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Zakład Fizyki Powierzchni i Nanostruktur

Strona domowa:

http://www.fnano.umcs.lublin.pl/

Kierownik zakładu:

prof. dr hab. Mieczysław Jałochowski

Pracownicy:

Kopciuszyński Marek
Korczak Zbigniew
Krawiec Mariusz
Kwapiński Tomasz
Marucha Witold
Paradowski Mieczysław
Stępniak-Dybala Agnieszka
Stróżak Mirosław
Zdyb Ryszard

Główne kierunki badawcze:

W Zakładzie dominuje eksperymentalna i teoretyczna problematyka fizyki metalicznych nanostruktur. Badany jest wpływ ograniczenia rozmiarów nanostrukturowych obiektów na ich strukturę elektronową. Monoatomowe łańcuchy atomów metali wytwarzane są na wysoceuporządkowanych, wicynalnych powierzchniach krzemu Si(335), Si(557), itp. Metaliczne studnie kwantowe i klastery są wytwarzane na atomowo gładkich powierzchniach Si(111)-(7x7)Au, Si(111)-(6x6)Au i innych rekonstruowanych powierzchniach krzemu. Prace doświadczalne prowadzone sa w pięciu układach ultrawysokiej próżni (UHV). Podstawowymi metodami ekperymentalymi są: dyfrakcja wysokoenergetycznych elektronów (RHEED), tunelowa mikroskopia skaningowa (STM), fotoemisja z kątową rozdzielczością (ARPES) i optyczna odbiciowa spektroskopia różnicowa.


Najważniejsze publikacje: Ukryj abstrakty


  1. Pawlikowska-Pawlęga, B. Misiak, L. E. Zarzyka, B. Paduch, R. Gawron, A. Gruszecki, W. I., FTIR, 1H NMR and EPR spectroscopy studies on the interaction of flavone apigenin with dipalmitoylphpsphatidylcholine liposomes, Biochimica et Biophysica Acta – Biomembranes, 1828(), 2013, 518-527

    Abstract:
    Apigenin (5,7,4′-trihydroxyflavone) is a cancer chemopreventive agent and a member of the family of plant flavonoids. Apigenin interaction with liposomes formed with dipalmitoylphosphatidylcholine (DPPC) was investigated by means of FTIR spectroscopy, 1H NMR and EPR techniques. Fluorescent microscopy and electron microscopy were applied to study the apigenin effects on colon myofibroblasts and human skin fibroblasts. The strong rigidifying effect of apigenin with respect to polar head groups was concluded on the basis of the action of the flavone on partition coefficient of Tempo spin label between the water and lipid phases. The ordering effect was also found in hydrophobic region at the depth monitored by 5-SASL and 16-SASL spin labels. The inclusion of apigenin to the membrane restricted the motional freedom of polar head groups lowering penetration of Pr3+ ions to the membranes. The 1H NMR technique supported also the restriction of motional freedom of the membrane in the hydrophobic region, especially in the zone of CH2 groups of alkyl chains. FTIR analysis showed that apigenin incorporates into DPPC liposomes via hydrogen bonding between its own hydroxyl groups and lipid polar head groups in the C–O–P–O–C segment. It is also very likely that hydroxyl groups of apigenin link with polar groups of DPPC by water bridges. Electron and fluorescence microscopic observations revealed changes in the internal membrane organization of the examined cells. In conclusion, the changes of the structural and dynamic properties of membranes can be crucial for processes involving tumor suppression signal transduction pathways and cell cycle regulation.

  2. Pawlikowska-Pawlęga, B. Misiak, L. E. Zarzyka, B. Paduch, R. Gawron, A. Gruszecki, W. I., Localization and interaction of genistein with model membranes formed with dipalmitoylphosphatidylcholine (DPPC), Biochimica et Biophysica Acta – Biomembranes, 1818(), 2012, 1785-1793

    Abstract:
    The effect of genistein on the liposomes formed with dipalmitoylphosphatidylcholine was studied with the application of Fourier-transform infrared spectroscopy, nuclear magnetic resonance (1H NMR) and electron paramagnetic resonance techniques. Membranous structures organization of human skin fibroblasts and colon myofibroblasts was also examined using fluorescence and electron microscopy. The strongest rigidifying effect of genistein with respect to polar head groups was concluded on the basis of the effect of the flavonoid on the shape of NMR lines attributed to –N+(CH3)3 groups. The rigidifying effect of genistein with respect to the hydrophobic core of lipid membranes was also concluded from the genistein-dependent broadening of the NMR lines assigned to –CH2 groups and terminal –CH3 groups of alkyl chains. EPR data supported ordering effect of genistein of the hydrophobic core in the liquid–crystalline phase (Lα). The analysis of the FTIR spectra of the two-component liposomes showed that genistein incorporates into DPPC membranes via hydrogen bonding between the lipid polar head groups in the C–O–P–O–C segment and its hydroxyl groups. Both fluorescence microscopy and ultrastructural observation revealed changes in membranous structures organization as aftermath of genistein treatment. In conclusion, genistein localized within membranes changes the properties of membrane that can be followed by the changes inside cells being crucial for pharmacological activity of genistein used in cancer or other disease treatment.

  3. Podleśny, J. Stochmal, A. Podleśna, A. Misiak, L.E., Effect of laser light treatment on some biochemical and physiological processes in seeds and seedlings of white lupine and faba bean, Plant Growth Regulation, 67(), 2012, 227-233

    Abstract:
    The aim of present study was to determine the changes of some biochemical and physiological processes, which occurred in seeds and seedlings of white lupine and faba bean after pre-sowing treatment with laser beams. It was found this treatment of seeds considerably increased the activity of amylolytic enzymes in seeds of both plants. The greatest differentiation of the enzymatic activity was noticed after 120 h from the time of sowing but the activity of these enzymes in the seeds of both tested plants was similar and it had the same course in time. The irradiated seeds of white lupine and faba bean had higher fresh weight at the time of imbibition than the seeds which were not treated with laser beams. It resulted in earlier and more uniform germination. The concentration of free radicals increased considerably in the seeds pre-treated with laser beams and the largest increase in seeds of both plant species was noticed after five exposures to laser beams. Treating seeds with laser beams considerably increased the amount of indole-3-acetic acid (IAA) in the germinating seeds. Three exposures of seeds caused the largest increase of this plant hormone content in the seeds. The activity of IAA in faba bean was slightly higher than in white lupine seeds. Pre-sowing stimulation with laser had a positive influence on the growth and development of seedlings, which had longer hypocotyl and roots in comparison to seedlings which grew from non irradiated seeds.

  4. M. Krawiec,M. Jałochowski, Array of double Au-Ag chains on the Si(557) surface, Applied Surface Science, 256(), 2010, 4813-4817

  5. T. Kwapiński, Conductance oscillations and charge waves in zigzag shaped quantum wires, Journal of Physics: Condensed Matter, 22(), 2010, 295303 (1-9)

  6. T. Kwapiński, Tip apex charged states in tunneling spectroscopy, Physica E, 43(), 2010, 333-337

  7. M. Krawiec, Structural model of the Au-induced Si(553) surface: Double Au rows, Physical Review B, 81(), 2010, 115436 (1-7)

  8. M. Krawiec,M. Jałochowski, Doping of the step-edge Si chain: Ag on a Si(557)-Au surface, Physical Review B, 82(), 2010, 195443 (1-7)

  9. T. Kwapiński,M. Jałochowski, Signature of tip electronic states on tunneling spectra, Surface Science, 604(), 2010, 1752-1756

  10. Z. Korczak,T. Kwapiński,P. Mazurek, Conductance of Pb on modified Si(335) vicinal surface, Surface Science, 604(), 2010, 54-58

  11. T. Kwapiński,S. Kohler,P. Hanggi, Electron transport across a quantum wire in the presence of electron leakage to a substrate, The European Physical Journal B, 78(), 2010, 75-81

  12. R. Zdyb, A. Pavlovska, E. Bauer, Strain engineering of magnetic anisotropy in thin ferromagnetic films, Journal of Physics: Condensed Matter, 21(), 2009, 314012 (1-6)

  13. M. Krawiec, Pb chains on reconstructed Si(335) surface, Physical Review B, 79(), 2009, 155438 (1-7)

  14. R. Zdyb, T. O. Mentes, A. Locatelli, M. A. Nino, E. Bauer, Magnetization and structure of ultrathin Fe films, Physical Review B, 80(), 2009, 184425 (1-9)

  15. T. Kwapiński, S. Kohler, P. Hanggi, Discontinuous conductance of bichromatically ac-gated quantum wires, Physical Review B, 79(), 2009, 155315 (1-6)

  16. A. Stępniak, P. Nita, M. Krawiec, M. Jałochowski, In and Si adatoms on Si(111)5x2-Au: Scanning tunneling microscopy and first-principles density functional calculations, Physical Review B, 80(), 2009, 125430 (1-8)

  17. HoangVuChung, M. Klevenz, R. Lovrincic, F. Neubrech, O. Skibbe, A. Pucci, P. Nita, M. Jałochowski, T. Nagao, Studies on gold atom chains and lead nanowires on silicon vicinal surfaces, Journal of Physics: Conference Series, 187(), 2009, 012025 (1-6)

  18. Krawiec, M., Thermoelectric transport through a quantum dot coupled to a normal metal and BCS superconductor, Acta Physica Polonica A, 114(), 2008, 115-122

  19. Klevenz, M. Neubrech, F. Lovrincic, R. Jałochowski, M. Pucci, A., Infrared resonances of self-assembled Pb nanorods, Applied Physics Letters, 92(), 2008, 133116 (1-3)

  20. Krawiec, M., First principles study of Si(335)-Au surface, Applied Surface Science, 254(), 2008, 4318-4321

  21. Zdyb, R., Influence of substarte morphology on Pb growth, Applied Surface Science, 254(), 2008, 4408-4413

  22. Kisiel, M. Skrobas, K. Jałochowski, M., Photoelectron diffraction effect In the highly ordered Si(557)/Pb surface, Applied Surface Science, 254(), 2008, 4313-4317

  23. Zdyb, R., Growth of Pb on Si(335) surface, Journal of Non-Crystalline Solids, 354(), 2008, 4176-4180

  24. Skrobas, K. Zdyb, R. Kisiel, M. Jałochowski, M., Band structure of In chains on Si(335)-Au, Materials Science-Poland, 26(), 2008, 55-61

  25. Douillard, L. Charra, F. Korczak, Z. Bachelot, R. Kostcheev, S. Lerondel, G. Adam, P. Royer, P., Short range plasmon resonators probed by photoemission electron microscopy, Nano Letters, 8(), 2008, 935-940

  26. Kwapiński, T. Krawiec, M. Jałochowski, M., STM tunneling through a quantum wire with a side-attached impurity, Physics Letters A, 372(), 2008, 154-161

  27. Hnatyuk, V. Stróżak, M., Optical response of Pb quantum wells on Si(111)-(6x6)-Au, Physics Letters A, 372(), 2008, 3882-3887

  28. Zdyb, R. Bauer, E., Coexistence of ferromagnetism and paramagnetism in a ferromagnetic monolayer, Physical Review Letters, 100(), 2008, 155704 (1-4)

  29. Zdyb, R., Quantum and finite size effects in ultrathin Fe films, Abstract of 14-th International Conference on Solid Films and Surfaces, (), 2008, 135-136

  30. Zdyb, R., Pb cluster array on Si(111)-(7x7) surface, Liverpool, Abstract of 25-th European Conference on Surface Science, , (), 2008, 81-82

  31. Krawiec, M., First principles study of Pb chains on Si(335)-Au surface, Liverpool, Abstract of 25-th European Conference on Surface Science, , (), 2008, 724-725

  32. Zdyb, R. Bauer, E., Spin reorientation transition in ultrathin Fe films on W(110), Abstract of 6-th international workshop on LEEM-PEEM, (), 2008, 35

  33. Kwapiński, T., Time-dependent and stationary electron transport through one-dimensional systems, AvH Foundation, Abstracts – Netzwerktagung, Augsburg, (), 2008, ISSN: 1864-824X, 43

  34. Krawiec, M., First principles study of Pb chains on Si(335)-Au surface,Ustroń-Katowice, Abstract of XXX International Conference of Theoretical Physics, (), 2008,

  35. Jałochowski, M., Monoatomowe łańcuchy na wicynalnych powierzchniach Si, Kraków, II Krajowa Konferencja Nanotechnologii, Książka streszczeń, (), 2008,

  36. Krawiec, M., Jednowymiarowe nanostruktury – czy poprawnie interpretujemy obrazy STM, Kraków, II Krajowa Konferencja Nanotechnologii, Książka streszczeń, (), 2008,

  37. Stępniak, A. Nita, P. Jałochowski, M., Jednowymiarowe struktury In na powierzchni Si(11 11 13), Kraków, II Krajowa Konferencja Nanotechnologii, Książka streszczeń, (), 2008,

  38. Nita, P. Stępniak, A. Jałochowski, M. Skrobas, K. Zdyb, R. Krawiec, M., Rekonstrukcje In na powierzchni Si(335)-Au,Kraków, II Krajowa Konferencja Nanotechnologii, Książka streszczeń, (), 2008,

  39. Skrobas, K. Zdyb, R. Jałochowski, M., Struktura elektronowa klasterów Pb i In na powierzchni Si(111)-(7x7), Kraków, II Krajowa Konferencja Nanotechnologii, Książka streszczeń, (), 2008,

  40. Nita, P. Stępniak, A. Jałochowski, M., Podwójne łańcuchy In na powierzchni Si(335)-Au, Zakopane, Streszczenia V Seminarium STM/AFM, wyd. IF UJ, Kraków 2008, (), 2008, U-6

  41. Kwapiński, T. Jałochowski, M. Nita, P. Stępniak, A., Asymetria przewodnictwa STS pojedynczych atomów, Zakopane, Streszczenia V Seminarium STM/AFM, wyd. IF UJ, Kraków 2008, (), 2008, P-I-12

  42. Stępniak, A. Nita, P. Krawiec, M. Jałochowski, M., Jednowymiarowe struktury z atomów In na powierzchni Si(111)-(5x2)-Au, Zakopane, Streszczenia V Seminarium STM/AFM, wyd. IF UJ, Kraków 2008, (), 2008, U-4

  43. Jałochowski, M. Stróżak, M. Zdyb, R., Klastery atomów Pb na powierzchni Si(111)-(7x7), Zakopane, Streszczenia V Seminarium STM/AFM, wyd. IF UJ, Kraków 2008, (), 2008, P-I-13

  44. Krawiec, M., Monoatomowe łańcuchy Pb na zrekonstruowanej powierzchni Si(335), Zakopane, Streszczenia V Seminarium STM/AFM, wyd. IF UJ, Kraków 2008, (), 2008, P-I-11

  45. Gorczyca, A. Krawiec, M. Maska, M.M. Mierzejewski, M., Particle-hole asymmetry in the scanning tunneling spectroscopy of the high temperature superconductors, Physica Status Solidi B-Basic Solid State Physics, 244(7), 2007, 2448-2452

    Abstract:
    There is still no consensus on the mechanism that is responsible for a particle-hole asymmetry observed in scanning tunneling spectroscopy of high-temperature superconductors. According to the most popular hypothesis this asymmetry results from strong Coulomb correlations in a nearly half-filled band. In the present paper we propose another mechanism that leads to such asymmetry. It originates from the coupling between the superconductor and the substrate that the system is deposed on. We show that this coupling gives rise to the particle-hole asymmetry only in the case of an anisotropic superconductivity. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  46. Krawiec, M. Jalochowski, M., Thermoelectric effects in STM tunneling through a monoatomic chain, Physica Status Solidi B-Basic Solid State Physics, 244(7), 2007, 2464-2469

    Abstract:
    We study thermoelectric properties of the system composed of a monoatomic chain on a surface and additional electrode coupled to the chain, which can be an STM tip. In particular, we are interested in thermopower, electric and thermal conductance, Wiedemann-Franz relation and thermoelectric figure of merit, which is a direct measure of the usefulness of the system for applications. We discuss the modifications of the STM wire topography due to temperature difference between the electrodes. Finally, we also make connection to STM experiment, in which the thermopower has been directly measured, showing different structure, not visible in topography spectra. (c) 2007 WILEY-NCH Verlag GmbH & Co. KGaA, Weinheim.

  47. Hnatyuk, V. Strozak, M., Optical and transport properties of ultrathin in quantized films, Journal Of Physics-Condensed Matter, 19(39), 2007, art. no.-396001

    Abstract:
    The differential reflectivity ( DR) has been measured during In deposition onto a Si( 111)-( 6 x 6) Au surface at 105 K. The experiments were done with s- polarized light from the infrared spectral range ( 0.26 - 0.35 eV). The imaginary part of the In dielectric function and mean free path ( scattering time) of the electrons were determined from the experimental data. The presented results show two series of maxima which repeat with a period of 1 and 3 monolayers of In( 111). They can be explained by periodical changes in surface roughness during layer- by- layer In growth and the influence of the quantum size effect ( QSE), respectively. It is shown that the DR technique is a suitable probe for characterization of the size effect phenomena and transport properties in ultrathin metallic films or quantum wells.

  48. Korczak, Z. Kwapinski, T., Electrical conductance at initial stage in epitaxial growth of Pb, Ag, Au and In on modified Si(111) surface, Surface Science, 601(16), 2007, 3324-3334

    Abstract:
    The electronic properties of thin metallic films of Pb, Ag, Au and In atoms deposited at 105 K on well defined metallic surface, i.e. Si(111)-(6 x 6)Au surface with 10 ML of annealed Pb, were investigated using four-point probe method in UHV condition. The structure of the substrate and deposited metals were monitored by the RHEED system. The electrical conductance, measured during the deposition of In and Pb atoms, shows the local minimum for the coverage equals about 0.3 ML whereas for An and Ag atoms the conductance decreases during the first monolayer growth. For An atoms the local maximum in the conductance was observed for the coverage about 0.55 ML, which can be connected with localized states. To describe theoretically the conductance behavior the tight-binding Hamiltonian and equation of motion for the Green's function were used and good qualitative agreement was obtained. (C) 2007 Elsevier B.V. All rights reserved.

  49. Pawllikowska-Pawlega, B. Gruszecki, W.I. Misiak, L. Paduch, R. Piersiak, T. Zarzyka, B. Pawelec, J. Gawron, A., Modification of membranes by quercetin, a naturally occurring flavonoid, via its incorporation in the polar head group, Biochimica et Biophysica Acta – Biomembranes , 1768(), 2007, 2195-2204

    Abstract:
    Quercetin is a naturally occurring flavonoid that has a lot of beneficial properties to human health. In this report, using the spin label technique, the influence of quercetin on the fluidity of multilamellar DPPC liposomes was studied. The polarity of the environment preferred by quercetin was also examined by determining the dependence of the position of electronic absorption maxima on dielectric properties of different environments. Autofluorescence of quercetin was also used to examine its distribution in cells. An additional aim of the study was to find how quercetin presence affects human skin fibroblasts. The results showed that incorporation of quercetin at physiological pH into DPPC liposomes caused changes in the partition coefficient of the Tempo spin label between water and polar head group phases. By determining the electronic absorption maxima, we observed that the chromophore of quercetin is localized in the polar head region. Fluorescence microscopy of HSF cells showed quercetin presence in the membrane, cytoplasm and inside the nucleus. Ultrastructural observation revealed some changes, especially in membranous structures, after flavonol treatment. From the results we have concluded that quercetin present in the membrane and other structures can cause changes within cells crucial for its pharmacological activity. © 2007 Elsevier B.V. All rights reserved.

  50. Krawiec, M., Compensation of the Kondo effect in quantum dots coupled to ferromagnetic leads within the equation of motion approach, Journal of Physics: Condensed Matter, 19(), 2007, 346234 (1-13)

  51. Kwapiński, T., Conductance oscillations of a quantum wire disturbed by an adatom, Journal of Physics: Condensed Matter, 19(), 2007, 176218 (1-9)

  52. Litak, G. Krawiec, M., Properties of the pi state induced by impurities in a d-wave superconductor, Physica C, 460-462(), 2007, 1066-1067

  53. Krawiec, M. Wysokiński, K.I., Thermoelectric phenomena in a quantum dot asymmetrically coupled to external leads, Physical Review B, 75(), 2007, 155330 (1-6)

  54. Kisiel, M. Skrobas, K. Zdyb, R. Mazurek, P. Jałochowski, M., Pb chains on ordered Si(335) surface, Physics Letters A, 364(), 2007, 152-156

  55. Tringides, M.C. Jalochowski, M. Bauer, E., Quantum size effects in metallic nanostructures, Physics Today, 60(), 2007, 50-54

  56. Pucci, A. Kost, F. Fahsold, G. Jalochowski, M., Infrared spectroscopy of Pb layer growth on Si(111), Physical Review B, 74(12), 2006, art. no.-125428

    Abstract:
    The growth of Pb films on Si(111)-(6x6) Au and on Si(111)-(7x7) Au at 120 K was investigated in situ with infrared transmittance spectroscopy. In the development of the transmission spectra with film thickness the formation of the crystalline layer, the layer-by-layer growth mode, and size effects can be identified. The infrared spectra are analyzed with the Drude model for the dielectric function. In order to get a good fit, both the parameters' plasma frequency and relaxation rate must become thickness dependent, which is explained in relation to the quantum-size effects and to the classical-size effect. This work is the first infrared spectroscopic study of quantum-size effect-related oscillations in metal films.

  57. Kisiel, M. Jalochowski, M. Zdyb, R., Morphology and electronic structure of submonolayer Pb on Si(111)-(6x6)Au, Physics Letters A, 357(2), 2006, 141-145

    Abstract:
    The electronic structure and the morphology of Pb adsorbed on the Si(111)-(6 x 6)Au substrate in the coverage range from 0.025 up to 1 monolayer are investigated with ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling microscopy (STM). The UPS measurements reveal two distinct peaks in the spectra. Correlation with the STM images allows us to associate one of them with single Pb atoms. The second peak emerges at coverage of 0.075 ML and is identified as a localized quantum well state. An evolution of these states as a function of the Pb coverage is determined. (c) 2006 Elsevier B.V. All rights reserved.

  58. Zdyb, R. Pavlovska, A. Jalochowski, M. Bauer, E., Self-organized Fe nanostructures on W(110), Surface Science, 600(8), 2006, 1586-1591

    Abstract:
    The magnetic domain structure of Fe wires, ribbons and islands with different shapes that have been prepared under ultra high vacuum conditions on W(I 10) are studied with spin polarized low energy electron microscopy. The dimensions of the nanostructures, which are of the order of tens and hundreds of nm, can be controlled by the temperature at which they are produced, by the average Fe coverage and by the substrate morphology. The domain structure of the nanostructures depends on their shape and is determined by the competition between magnetoelastic.. shape and magnetocrystalline anisotropies. (c) 2006 Elsevier B.V. All rights reserved.

  59. Krawiec, M. Jalochowski, M. Kisiel, M., High resolution scanning tunneling spectroscopy of ultrathin Pb on Si(111)-(6 x 6) substrate, Surface Science, 600(8), 2006, 1641-1645

    Abstract:
    The electronic structure of Si(111)-(6 x 6)Au surface covered with sub-monolayer amount of Pb is investigated using scanning tunneling spectroscopy. Already in small islands of Pb with thickness of 1 ML Pb-(111) and with the diameter of only about 2 nm we detected the quantized electronic state with energy 0.55 eV below the Fermi level. Similarly, the I(V) characteristics made for the Si(111)-(6 x 6)Au surface reveal a localized energy state 0.3 eV below the Fermi level. These energies result from fitting of the theoretical curves to the experimental data. The calculations are based on tight binding Hubbard model. The theoretical calculations clearly show prominent modification of the I(V) curve due to variation of electronic and topographic properties of the STM tip apex. (c) 2006 Elsevier B.V.. All rights reserved.

  60. Krawiec, M. Kwapinski, T. Jalochowski, M., Double nonequivalent chain structure on a vicinal Si(557)-Au surface, Physical Review B, 73(7), 2006, art. no.-075415

    Abstract:
    We study electronic and topographic properties of the vicinal Si(557)-Au surface using scanning-tunneling microscopy (STM) and a reflection of high-energy electron diffraction technique. STM data reveal double wire structures along terraces. Moreover, the behavior of the voltage-dependent STM tip-surface distance is different in different chains. While the one chain shows oscillations of the distance which are sensitive to the sign of the voltage bias, the oscillations in the other chain remain unchanged with respect to the positive or negative biases. This suggests that one wire has metallic character while the other one has a semiconducting one. The experimental results are supplemented by theoretical calculations within tight binding model suggesting that the observed chains are made of different materials, one gold and the other silicon.

  61. Korczak, Z. Kwapinski, T., Electrical conductance at initial stage in epitaxial growth of Pb on modified Si(111) surface, Surface Science, 600(8), 2006, 1650-1653

    Abstract:
    The electrical conductance and RHEED intensities as is a function of the coverage have been measured during Pb depositions at 105 K on Si(111)-(6 x 6)Au with up to 4.2 ML of annealed Pb. The experiments show the strong influence of used substrates on the behavior of the conductance during the epitaxy of Pb atoms, especially for very initial stage of growth. Oscillations of the conductance during the layer-by- layer growth are correlated with RHEED intensity oscillations. The analysis of the conductance behavior is made according to the theory described by Trivedi and Aschcroft [N. Trivedi, N. Aschcroft, Phys. Rev. B 38 (1988) 12298]. (c) 2006 Elsevier B.V. All rights reserved.

  62. Krawiec, M., Residual Kondo effect in quantum dot coupled to half-metallic ferromagnets, Journal of Physics-Condensed Matter, 18(29), 2006, 6923-6936

    Abstract:
    We study the Kondo effect in a quantum dot coupled to half- metallic ferromagnetic electrodes in the regime of strong on- dot correlations. Using the equation of motion technique for non-equilibrium Green functions in the slave boson representation, we show that the Kondo effect is not completely suppressed for anti-parallel magnetization of the leads. In the parallel configuration, there is no Kondo effect but there is an effect associated with elastic co-tunnelling which, in turn, leads to similar behaviour of the local (on-dot) density of states (LDOS) as the usual Kondo effect. Namely, the LDOS shows the temperature-dependent resonance at the Fermi energy, which splits with the bias voltage and the magnetic field. Moreover, unlike for non-magnetic or not fully polarized ferromagnetic leads, only the minority spin electrons can form such resonance in the density of states. However, this resonance cannot be observed directly in the transport measurements, and we give some clues how to identify the effect in such systems.

  63. Litak, G. Krawiec, M., Superconducting pairing amplitude and local density of states in presence of repulsive centers, Physica B-Condensed Matter, 378-80(), 2006, 434-436

    Abstract:
    We study the properties of superconductor in presence of a finite concentration of repulsive centers. The superconductor is described by the negative U Hubbard model while repulsive centers are treated as randomly distributed impurities with repulsive interaction. Analyzing the paring potential and local density of states at impurity sites we find a wide range of the system parameters where the it-like state could possibly be realized. Comparison of our results to the single repulsive center case is also given. (c) 2006 Elsevier B.V. All rights reserved.

  64. Krawiec, M. Wysokinski, K. I., Thermoelectric effects in strongly interacting quantum dot coupled to, Physica B-Condensed Matter, 378-80(), 2006, 933-934

    Abstract:
    We study thermoelectric effects in Kondo correlated quantum dot coupled to ferromagnetic electrodes by calculating thermopower S in the Kondo regime as function of on-dot energy level and temperature. The system is represented by the Anderson model and the results agree well with those recently measured for a quantum dot coupled to nonmagnetic leads. For magnetic electrodes, one observes marked dependence of S on the degree of their polarisation. (c) 2006 Elsevier B.V. All rights reserved.

  65. Annett, J. F. Krawiec, M. Gyorffy, B. L., Origin of spontaneous currents in a superconductor- ferromagnetic proximity system, Physica C-Superconductivity and Its Applications, 437-38(), 2006, 7-10

    Abstract:
    We have previously shown that a ferromagnet-superconductor heterostructure may possess a spontaneous current circulation parallel to the interface. This current is caused by Andreev bound states in the thin ferromagnetic layer, and can be fully spin-polarized. Here we investigate the total energy of the system in cases where the current either does or does not flow. We show that the current is a true quantum ground state effect, and examine the effect of the current on the different contributions to the total energy. (c) 2005 Elsevier B.V. All rights reserved.

  66. Krawiec, M. Annett, J. F. Gyorffy, B. L., Spontaneous currents in a ferromagnet-normal metal- superconductor trilayer, Acta Physica Polonica A, 109(4-5), 2006, 507-512

    Abstract:
    We discuss the ground state properties of the system composed of a normal metal sandwiched between ferromagnet and superconductor within a tight binding Hubbard model. We solved the spin-polarized Hartree-Fock-Gorkov equations together with the Maxwell equation (Ampere's law) and found a proximity induced F'ulde-Ferrell-Larkin-Ovchinnikov state in this system. Here we show that the inclusion of the normal metal layer in between those subsystems does not necessarily lead to the suppression of the Fulde-Ferrell-Larkin-Ovchinnikov phase. Moreover, we found that depending on the thickness of the normal metal slab the system can be switched periodically between the state with the spontaneous current flowing to that one with no current. All these effects can be explained in terms of the Andreev bound states formed in such structures.

  67. Krawiec, M. Kwapinski, T., Electron transport through a strongly correlated monoatomic chain, Surface Science, 600(8), 2006, 1697-1701

    Abstract:
    We study transport properties of a strongly correlated monoatomic chain coupled to metallic leads. Our system is described by tight binding Hubbard-like model in the limit of strong on-site electron-electron interactions in the wire. The equation of motion technique in the slave boson representation has been applied to obtain analytical and numerical results. Calculated linear conductance of the system shows oscillatory behavior as a function of the wire length. We have also found similar oscillations of the electron charge in the system. Moreover our results show spontaneous spin polarization in the wire. Finally, we compare our results with those for non- interacting chain and discuss their modifications due to the Coulomb interactions in the system. (c) 2006 Elsevier B.V. All rights reserved.

  68. Krawiec, M. Wysokinski, K. I., Thermoelectric effects in strongly interacting quantum dot coupled to ferromagnetic leads, Physical Review B, 73(7), 2006, art. no.-075307

    Abstract:
    We study thermoelectric effects in a Kondo correlated quantum dot coupled to ferromagnetic electrodes by calculating conductance, thermopower, and thermal conductance in the Kondo regime. We also study the effect of the asymmetry in the coupling to the leads, which has important consequences for antiparallel magnetization configuration. We discuss the thermoelectric figure of merit, tunnel magnetoresistance, and violation of the Wiedemann-Franz law in this system. The results agree with recently measured thermopower of the quantum dot defined in a two-dimensional electron gas.

  69. Kwapinski, T., Charge fluctuations in a perfect and disturbed quantum wire, Journal of Physics-Condensed Matter, 18(31), 2006, 7313-7326

    Abstract:
    The tight-binding Hamiltonian and retarded Green function formalism are used to study the local and total density of states of a monatomic quantum wire. An additional atom (adatom) can be coupled with the wire at its side. Also the local and average charges of the perfect and disturbed wire are shown and the analytical formula for the local density of states at each site is obtained. The local density of states at each atom in a wire which consists of an even number of atoms is characterized by minima at the Fermi level, in comparison with a wire disturbed by an adatom, where the density of states is characterized by local peaks. Charge fluctuations ( waves) are observed in the wire for the case when the condition for the conductance oscillations is satisfied. For the single electron energies of a wire localized above the Fermi energy the local charge along the wire forms a wave curve which possesses one maximum less than for energies localized below the Fermi level.

  70. Mazurek, P. Paprocki, K. Mitura, Z., Investigation of Si-Au vicinal surfaces using scanning tunnelling microscopy and reflection high-energy electron diffraction, Journal of Microscopy-Oxford, 224(), 2006, 125-127

    Abstract:
    Silicon vicinal surfaces can be successfully used as substrates for the preparation of one-dimensional nanostructures. The quality of the structures prepared may be controlled using scanning tunnelling microscopy, as shown in this work. Additionally, it is possible to obtain valuable information using reflection high-energy electron diffraction. A typical way of employing reflection high-energy electron diffraction is to observe patterns of scattered electrons on a screen. However, it is possible to obtain more detailed information on the arrangement of atoms at the surface if azimuthal plots are collected. Azimuthal plots are measured by recording the intensity of specularly reflected electrons during the rotation of the sample around an axis perpendicular to its surface. So far, only flat surfaces have been examined in such a way. In this work, it is shown that such data, containing interesting features, can also be collected for vicinal surfaces.

  71. Bauer, E. Belkhou, R. Cherifi, S. Hertel, R. Heun, S. Locatelli, A. Pavlovska, A. Zdyb, R. Agarwal, N. Wang, H., Microscopy of mesoscopic ferromagnetic systems with slow electrons, Surface and Interface Analysis, 38(12-13), 2006, 1622-1627

    Abstract:
    Mesoscopic ferromagnetic systems are not only of practical interest for high density recording and storage devices but also as models of cooperative phenomena in low dimensions. The magnetization distribution in such systems is studied in this paper by X-ray Magnetic Circular Dichroism Photo Emission Microscopy (XMCDPEEM), using thin rectangular and ring-shaped patterned Co films and by Spin-Polarized Low Energy Electron Microscopy (SPLEEM), using epitaxial Fe nanostructures. Copyright (C) 2006 John Wiley & Sons, Ltd.

  72. Kisiel, M. Skrobas, K. Jalochowski, M., Angle-resolved photoemission of ultrathin Pb films on Si(111)- (6x6)Au: quantum size effect, Optica Applicata, 35(3), 2005, 443-448

    Abstract:
    The electronic band structure of extremely thin (from 1 to 8 monoatomic layer (ML) thick) epitaxial Pb(111) films grown at low temperatures in ultrahigh vacuum (UHV) condition on Si(111)-(6x6)Au substrate is studied with angle-resolved photoelectron spectroscopy (ARPES). The morphology of the Pb film is determined with scanning tunneling microscopy (STM). Normal-emission photoelectron spectra recorded at the sample temperature of 130 K reveal quantum well states (QWS) characteristic of quantization perpendicular to the film surface. The energies of these states as a function of the number of the Pb(l 11) monoatomic layers are determined and compared with calculated in terms of the Bohr-Sommerfeld phase accumulation model.

  73. Kisiel, M. Skrobas, K. Zdyb, R. Jalochowski, M., Band structure of Au monoatomic chains on Si(335) and Si(557) surfaces, Optica Applicata, 35(3), 2005, 449-455

    Abstract:
    The electronic band structure of the Si(557) and Si(335) surfaces covered with monoatomic Au chains produced in UHV conditions, is investigated in detail by. angle-resolved photoelectron spectroscopy (ARPES), especially for the surface state bands near the Fermi energy. The ARPES spectra in the plane parallel to step edges for Si(557)-Au vicinal surface show strongly dispersive electron energy bands, characteristic of one-dimensional structure. The band dispersion is also calculated within tight-binding model, with two adjustable coupling parameters t(1) and t(2), for the first and second neighbors along the chains, respectively, and compared with that determined from the photoemission experiment. The scanning tunneling microscopy (STM) imaging and reflection high energy electron diffraction (RHEED) studies enabled us to determine atomic chain separation and its internal structure. The study shows that the structural anisotropy of these surfaces induces highly anisotropic electronic structure.

  74. Krawiec, M. Kwapinski, T. Jalochowski, M., Scanning tunneling microscopy of monoatomic gold chains on vicinal Si(335) surface: experimental and theoretical study, Physica Status Solidi B-Basic Solid State Physics, 242(2), 2005, 332-336

    Abstract:
    We study electronic and topographic properties of the Si(335) surface, containing Au wires parallel to the steps. We use scanning tunneling microscopy (STM) supplemented by reflection of high energy electron diffraction (RHEED) technique. The STM data show the space and voltage dependent oscillations of the distance between STM tip and the surface which can be explained within one hand tight binding Hubbard model. We calculate the STM current using nonequilibrium Keldysh Green function formalism. (c) 2(9)5 WILFY-VCH Verlag GmbH W Co KGaA. Weinheim.

  75. Litak, G. Krawiec, M., 'pi-state' induced by impurities with a repulsive interaction, Physica Status Solidi B-Basic Solid State Physics, 242(2), 2005, 438-442

    Abstract:
    We study the properties of a quantum impurity embedded in a superconducting host. The superconductor is described by the negative U Hubbard model while the impurity introduces a repulsive interaction to the system. We discuss the influence of this 'on-impurity' Coulomb repulsion on the local properties, (density of states, electron pairing) of the superconductor. We show the condition of pi-like behaviour. defined as two subsystems having a phase difference of pi, in the system by using a proper combination of attractive pairing interaction and repulsive one located at impurity site.

  76. Kwapinski, T., Conductance oscillations of a metallic quantum wire, Journal of Physics-Condensed Matter, 17(37), 2005, 5849-5858

    Abstract:
    The electron transport through a monatomic metallic wire connected to leads is investigated using the tight-binding Hamiltonian and the Green function technique. Analytical formulae for the transmittance are derived and M-atom oscillations of the conductance versus the length of the wire are found. Maxima of the transmittance function versus the energy, for a wire consisting of N atoms, determine the (N + 1) period of the conductance. The periods of conductance oscillations are discussed and the local and average quantum wire charges are presented. The average charge of the wire is linked with the period of the conductance oscillations and for M-atom periodicity there are possible (M - 1) average occupations of the wire states.

  77. Kwapinski, T. Taranko, R. Taranko, E., Photon-assisted electron transport through a three-terminal quantum dot system with nonresonant tunneling channels, Physical Review B, 72(12), 2005, art. no.-125312

    Abstract:
    We have studied the electron transport through a quantum dot coupled to three leads in the presence of external microwave fields supplied to different parts of the considered mesoscopic system. Additionally, we introduced a possible nonresonant tunneling channel between leads. The quantum dot charge and currents were determined in terms of the appropriate evolution operator matrix elements and under the wide-band limit the analytical formulas for time-averaged currents and differential conductance were obtained. We have also examined the response of the considered system on the rectangular-pulse modulation imposed on different quantum dot-lead barriers as well as the time dependence of currents flowing in response to suddenly removed (or included) connection of a quantum dot with one of the leads.

  78. Sujak, A. Gabrielska, J. Milanowska, J. Mazurek, P. Strzalka, K. Gruszeeki, W. I., Studies on canthaxanthin in lipid membranes, Biochimica Et Biophysica Acta-Biomembranes, 1712(1), 2005, 17-28

    Abstract:
    Polar carotenoid pigment - canthaxanthin - has been found to interfere with the organization of biological membranes, in particular of the retina membranes of an eye of primates. The organization of lipid membranes formed with dipalmitoylphosphatidylcholine (DPPC) and egg yolk phosphatidylcholine containing canthaxanthin was studied by means of several techniques including: electronic absorption spectroscopy, linear dichroism, X-ray diffractometry, H-1-NMR spectroscopy and FTIR spectroscopy. It appears that canthaxanthin present in the lipid membranes at relatively low concentration (below 1 mol% with respect to lipid) modifies significantly physical properties of the membranes. In particular, canthaxanthin (i) exerts restrictions to the segmental molecular motion of lipid molecules both in the headgroup region and in the hydrophobic core of the bilayer, (ii) promotes extended conformation of alkyl lipid chains, (iii) modifies the surface of the lipid membranes (in particular in the gel state, L-beta') and promotes the aggregation of lipid vesicles. It is concluded that canthaxanthin incorporated into lipid membranes is distributed among two pools: one spanning the lipid bilayer roughly perpendicularly to the surface of the membrane and one parallel to the membrane, localized in the headgroup region. The population of the horizontal fraction increases with the increase in the concentration of the pigment in the lipid phase. Such a conclusion is supported by the linear dichroism analysis of the oriented lipid multibilayers containing canthaxanthin: The mean angle between the dipole transition moment and the axis normal to the plane of the membrane was determined as 20 +/- 3 degrees at 0.5 mol% and 47 +/- 3 degrees at 2 mol% canthaxanthin. The analysis of the absorption spectra of canthaxanthin in the lipid phase and H-1-NMR spectra of lipids point to the exceptionally low aggregation threshold of the pigment in the membrane environment (similar to 1 mol%). All results demonstrate a very strong modifying effect of canthaxanthin with respect to the dynamic and structural properties of lipid membranes. (c) 2005 Elsevier B.V. All rights reserved.

  79. Podleśny, J. Misiak, L. E. Podleśna, A. Pietruszewski, S., Concentration of free radicals in pea seeds after pre-sowing treatment with magnetic field, International Agrophysics, 19(), 2005, 243-249

    Abstract:
    The aim of the research was the estimation of seed lot magnetic stimulation effect on free radicals concentration and dynamics of pea seeds germination. The first factor were two cultivars of pea: Rola (traditional form) and Piast (afila type), the second factor were the 3 exposure doses of magnetic field intensity: D0 - no stimulation (control), Dl - 10 750 Jm3s and D2 - 85 987 Jm3s. The stimulated seeds of both pea forms showed faster uptake of water and achieved larger mass during the seed imbibition in comparison to the seeds without stimulation. It was found that earlier and more steady emergence of these plants was a con­sequence of this process. Pea seedlings which were grown from stimulated seeds achieved in the following successive dates of measurement significantly larger hypocotyl and roots length in comparison to the seedlings without stimulation with magnetic field. A significant increase of free radicals concentration was ob­served in the seeds which were pre-sowing treated with magnetic field. There was no significant effect of the stimulation on the free radicals concentration in the organs of young pea plants grown from seeds of the varieties under examination. Free radicals num­bers in the leaves, stems and roots did not differ significantly from those which were found in the particular organs of plants which were grown from non-stimulated seeds. The laboratory tests did not show any larger number of free radicals in the seeds harvested from the plants which were grown from the stimulated seeds.

  80. Zdyb, R. Pavlovska, A. Locatelli, A. Heun, S. Cherifi, S. Belkhou, R. Bauer, E., Imaging low-dimensional magnetism with slow electrons, Applied Surface Science, 249(1-4), 2005, 38-44

    Abstract:
    Two aspects of low-dimensional magnetism are discussed: the spin-dependent quantization effects in perfect two-dimensional single crystal layers and the magnetic domain structure of submicron magnetic patterns. Both require high lateral resolution and surface sensitivity. This is provided by spin- polarized low energy electron microscopy (SPLEEM) and X-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM). (c) 2004 Elsevier B.V. All rights reserved.

  81. Zdyb, R. Locatelli, A. Heun, S. Cherifi, S. Belkhou, R. Bauer, E., Nanomagnetism studies with spin-polarized low-energy electron microscopy and x-ray magnetic circular dichroism photoemission electron microscopy, Surface and Interface Analysis, 37(2), 2005, 239-243

    Abstract:
    The spin reorientation transition (SRT) of ultrathin Fe-Co alloy films on an Au(111) surface and the magnetic/structural phase transition of epitaxial MnAs films on a GaAs(100) surface are studied by two electron microscopic techniques with very high surface sensitivity, i.e. spin-polarized to energy electron microscopy (SPLEEM) and x-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM), combined with low-energy electron microscopy (LEEM) and low- energy electron diffraction (LEED), respectively. A new SRT mechanism is found and the interrelation between ferromagnetism and structure is elucidated. Copyright (C) 2005 John Wiley Sons, Ltd.

  82. Jalochowski, M. Strozak, M. Zdyb, R., Optical recognition of structural and electronic transformation of Pb ultrathin films, Journal of Physics-Condensed Matter, 16(39), 2004, S4345-S4352

    Abstract:
    In this study, the transformation of ultrathin Pb film on a Si(111)-(7 x 7) surface from amorphous-like to crystalline state is examined at low temperatures during the film growth by measuring the differential reflectance (DR) DeltaR/R, as a function of film thickness. The experiments were performed under ultrahigh vacuum conditions in the visible and infrared spectral range. The determined imaginary part of the Pb dielectric function changes steeply at the critical thickness of the film of about 5 monoatomic Pb(111) layers. High energy electron diffraction (RHEED) and scanning tunnelling microscopy (STM) studies revealed a film with fine granular morphology before the structural transition and a well ordered epitaxial layer after the transformation. The variation of the optical (AC) conductivity was compared with DC electrical conductance data. We show that the DR technique can be efficiently used to characterize structural and electronic changes in ultrathin metallic films.

  83. Zdyb, R. Jalochowski, M. Strozak, M., Quantum size effect in absorption of low energy electrons in Pb layers, Vacuum, 74(2), 2004, 217-222

    Abstract:
    Absorption of low-energy electrons in Pb ultrathin layers grown on a Si(111)-(6 x 6)Au substrate has been measured as a function of the incident electron energy and of the film thickness. The thickness-dependent curves of the current revealed two distinct features. One of them is associated with the quantum size effect and showed the characteristic oscillatory behavior with the periodicity determined by the film thickness. The other, independent of the film thickness, was attributed to the bulk band structure of Pb. On the basis of the changes in the quantum size oscillations peak position as a function of the transmitted electron energy, and of the layer thickness, the electronic band structure of Pb 8-20eV above the vacuum level has been determined in the GammaL direction. (C) 2004 Elsevier Ltd. All rights reserved.

  84. Strozak, M. Hnatyuk, V. Jalochowski, M., Optical properties of Pb nanowires on Si(335), Vacuum, 74(2), 2004, 241-245

    Abstract:
    Pb films and self-assembled nanowires on Si(3 3 5) grown at temperature equal to 265 K are investigated by optical reflectance method and scanning tunneling microscopy. In the optical studies s-polarized light with the photon energy from 0.35 to 2.0 eV was used. The measurements were performed during the Pb deposition, for two orientations of the sample: with the light electric field along, and perpendicularly to the Pb nanowires. Two thickness ranges were distinguished: first, for the coverages less than 2 ML, and second, for the larger coverages. The large anisotropy in the optical reflectance was observed in the second range of the thicknesses. The anisotropy was caused by the presence of self-assembled, parallelly aligned metallic nanowires. For the two orthogonal orientations of the sample the reflectance ratio as high as 3.8 was observed. (C) 2004 Elsevier Ltd. All rights reserved.

  85. Krawiec, M. Gyorffy, B. L. Annett, J. F., Current-carrying Andreev bound states in a superconductor- ferromagnet proximity system, Physical Review B, 70(13), 2004, art. no.-134519

    Abstract:
    We study the ground-state properties of a ferromagnet- superconductor heterostructure on the basis of a quasiclassical theory. We have solved the Eilenberger equations together with Maxwell's equation fully self-consistently and found that due to the proximity effect a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO)-like state is realized in such a system. Moreover, this state has oscillations of the pairing amplitude in either one or two directions, depending on the exchange splitting and thickness of the ferromagnet. In particular, using semiclassical arguments (Bohr-Sommerfeld quantization rule) we show that owing to the presence of the Andreev bound states in the ferromagnet, a spontaneous current in the ground state is generated as a hallmark of the FFLO state in the direction parallel to the interface. We also discuss the effects of the elastic disorder and finite transparency of the interface on the properties of the FFLO state in the system.

  86. Krawiec, M. Wysokinski, K. I., Electron transport through a strongly interacting quantum dot coupled to a normal metal and BCS superconductor, Superconductor Science & Technology, 17(1), 2004, 103-112

    Abstract:
    We study electron transport through a quantum dot coupled to a normal metal and BCS-like superconductor (N-QD-S) in the presence of the Kondo effect and Andreev scattering. The system is described by the single impurity Anderson model in the limit of strong on-dot interaction. To study electron transport, we use the recently proposed equation of motion technique for the Keldysh non-equilibrium Green's function together with the modified slave boson approach. We derive the formula for the current which contains various tunnelling processes and we apply it to a study of the transport through the system. We find that the Andreev conductance is strongly suppressed and there is no zero-bias (Kondo) anomaly in the differential conductance. We discuss the effects of the particle-hole asymmetry in the electrodes as well as the asymmetry in the couplings.

  87. Kwapinski, T., Time-dependent electron transport through a quantum wire, Physical Review B, 69(15), 2004, art. no.-153303

    Abstract:
    The influence of the external time-dependent field on electron transport through a quantum wire is studied using the model Hamiltonian and evolution operator method. The conductance, transmission coefficient, and current flowing through the wire connected to leads are obtained. It is shown that the average current can be expressed by the corresponding matrix elements of the evolution operator and it satisfies the Landauer-like formula. The sideband peaks in the average current and transmittance are investigated. In contrast to the even-odd conductance oscillation the six-atom period was found in the case where ac external field is applied to the wire.

  88. Taranko, R. Kwapinski, T. Taranko, E., Influence of microwave fields on electron transport through a quantum dot in the presence of direct tunneling between leads, Physical Review B, 69(16), 2004, art. no.-165306

    Abstract:
    We consider the time-dependent electron transport through a quantum dot coupled to two leads in the presence of the additional overdot (bridge) tunneling channel. By using the evolution operator method together with the wide-band limit approximation we derived the analytical formulas for the quantum dot charge and current flowing in the system. The influence of the external microwave field on the current and the derivatives of the current with respect to the gate and source-drain voltages has been investigated for a wide range of parameters. The most characteristic feature of including the additional overdot tunneling channel is an asymmetric behavior of the function describing the dependence of the average current vs the gate voltage or the differential conductance vs the source-drain voltage.

  89. Kwapinski, T., Electron transport through a few-atom system, Vacuum, 74(2), 2004, 201-205

    Abstract:
    The electron transport through a few-atom chain between two metallic leads is investigated. The additional atom is coupled to the quantum wire at its side and causes disturbance in the current flowing through the system. The evolution operator method is used to obtain the time-response of the current on adding another atom to the quantum wire, the stationary current flowing through the system and transmittance. It is shown that the current in the symmetrical case satisfies the Landauer-like formula. (C) 2004 Elsevier Ltd. All rights reserved.

  90. Mazurek, P. Daniluk, A. Paprocki, K., Substrate temperature control from RHEED intensity measurements, Vacuum, 72(4), 2004, 363-367

    Abstract:
    Substrate temperature is an importance parameter controlling nucleation and growth dynamics during the thin film epitaxy in MBE system. The most covenant methods able to determine the substrate temperature is based on some calibration procedures, where substrate temperature is calculated as a function of electric power dissipated in heater system. This paper presents possibility of substrate temperature control based on reflection high-energy electron diffraction (RHEED) intensity measurements as in situ technique. Temperature dependence of the specularly reflected electron beam intensity versus the substrate temperature is predicted by dynamical theory of electron scattering. The theoretical RHEED intensity dependence versus Si(111) substrate temperature was obtained from one- dimensional rocking-curve calculation. (C) 2003 Elsevier Ltd. All rights reserved.

  91. Paradowski, M. L. Misiak, L. E., Gd3+-RE3+ exchange interactions in rare-earth fluoride crystals (RE = Ce, Nd, Yb), Acta Physica Polonica A, 105(5), 2004, 445-457

    Abstract:
    The investigation of Gd3+-doped LaFi(3) La0.9Ce0.1F3, CeF3, La0.9Nd0.1F3, LiYF4, and LiY0.9Yb0.1 F-4 single crystals at 4.2 K was carried out in order to study the Gd3+ -R,E3+ exchange interactions (RE = Ce, Nd, Yb). The exchange interactions were estimated by the application of the molecular-field model at liquid-lielium temperature, using the g shift from the isostructural diamagnetic hosts LaFi(3) and LiYF4 to the paramagnetic hosts. The lattice dynamics is studied by analysing spin-Hamiltonian parameters in the light of the superposition model and the rotational invariance theory for phonon-induced contributions to spin-Hamiltonian parameters. It is suggested from the rotational invariance mechanism for phonon-induced contributions to spin-Hamiltonian parameters that the rotational contributions influence the exchange interactions significantly. Further, the distoritions caused by the La3+/Ce3+, La3+/Nd3+, and Y3+/Yb3+ substitutions , affect significantly the 4f(7) elect ron-ph on on interactions, as well as the exchange interactions. The magnitude of the isotropic exchange interactions is larger for more symmetrical charge distribution of the 4f(7) Shell.

  92. Jalochowski, M., Si(111)-(6 x 6)Au surface morphology and nucleation of Pb at low temperature, Progress in Surface Science, 74(1-8), 2003, 97-107

    Abstract:
    The morphologies of the Si(111)-(6 x 6)Au surface and the nucleation of Pb have been investigated at temperatures below room temperature using scanning tunnelling microscopy (STM). The STM scans of the clean Si(111)-(6 x 6)Au surface revealed exceptionally rich and strongly bias-dependent details within the unit cell. After deposition of about 0.01 ML of Pb(I 11), at temperatures above 180 K, the single Pb atoms formed a two- dimensional mesh with (6 x 6)-Au periodicity. In this early stage of deposition, the Pb atoms occupied predominantly one specific site of the (6 x 6) unit cell. The local symmetry of this site determined the further growth of the Pb layer. As a consequence, the structure of the Pb layer on Si(111)(6 x 6)Au is rotated of 30degrees relative to that of the Pb layer on Si(111)-(7 x 7). (C) 2003 Elsevier Ltd. All rights reserved.

  93. Jalochowski, M. Strozak, M. Zdyb, R., Reflectance anisotropy during growth of Pb nanowires on well ordered Si(335) surface, Applied Surface Science, 211(1-4), 2003, 209-215

    Abstract:
    Ultrathin Pb films on Si(3 3 5) deposited at temperatures ranging from 105 to 305 K are investigated by optical reflectance method, scanning tunneling microscopy, and reflection high energy electron diffraction. From the reflectance data for light with photon energy of 0.6 eV, the imaginary part of the Pb dielectric function epsilon(2)(Pb) is determined. For films with coverages below about 2 monoatomic layers (ML), independent on the substrate temperature, epsilon(2)(Pb) linearly increases with the average film thickness. For larger Pb coverages, it strongly depends on the deposition temperature. The observed variation of the dielectric function is correlated with structural and topographic transitions of Pb ultrathin films growing on Si(3 3 5) surface. The origin of the optical anisotropy as a consequence of self-assembling of Pb nanowires on well ordered Si(3 3 5) substrate is discussed. (C) 2003 Elsevier Science B.V. All rights reserved.

  94. Kuroiwa, N. Fukushima, Y. Rajasekar, P. Neddermeyer, H. Jalochowski, M. Bauer, E. Yasue, T. Koshikawa, T., Copper nanostructure formation and structure analysis on hydrogen-terminated Si(111) surface, Surface and Interface Analysis, 35(1), 2003, 24-28

    Abstract:
    The growth of Cu nanostructures on the hydrogen-terminated Si(111) surface was studied by scanning tunnelling microscopy (STM). On the hydrogen-terminated Si(111) surface, small Cu nanostructures scatter mainly on the terraces and a few structures along the steps and domain boundaries at a deposition temperature of similar to310degreesC: the shape of the nanostructure is round or triangular, and the face is not clear. At similar to340degreesC, the Cu nanostructures form preferentially at steps and domain boundaries of the substrate: the shape is triangular with truncated corners and the nanostructures have some facets. The top face has an inclination angle of similar to6degrees and the side face has one of similar to35degrees. On the top face, mono-atomic steps can be seen similar to0.8 mn apart. From these results, it is concluded that the Cu nanostructure has a {554} facet on top and a {110} facet on the side. Copyright (C) 2003 John Wiley Sons, Ltd.

  95. Kwapinski, T. Taranko, R., Time-dependent transport through a quantum dot with the over- dot (bridge) additional tunneling channel, Physica E-Low-Dimensional Systems & Nanostructures, 18(4), 2003, 402-411

    Abstract:
    The time-dependent, electron transport through a quantum dot with the additional over-dot (bridge) tunneling channel within the evolution operator technique has been studied. The microwave,field applied to the leads and quantum dot has been considered and influence, of the time-dependent shift of corresponding energy, levels on the quantum dot charge and current flowing, in the system, its time-averaged values and derivatives of the average current with respect to the gate and source-drain bias voltages have been investigated. The influence of the over-dot tunneling channel on the photon- assisted tunneling has been also studied. (C) 2003 Elsevier Science B.V. All rights reserved.

  96. Pawlikowska-Pawlega, B. Gruszecki, W. I. Misiak, L. E. Gawron, A., The study of the quercetin action on human erythrocyte membranes, Biochemical Pharmacology, 66(4), 2003, 605-612

    Abstract:
    Quercetin is a naturally occurring flavonoid that exerts multiple pharmacological effects. In our previous study, we showed that quercetin greatly affects the lipid membrane. In this report, a study of quercetin on human erythrocyte membrane has been performed to determine the influence of this flavonoid on the fluidity and the conformational changes of membrane proteins. An additional aim of the study was to find how quercetin presence affects the resistance of membrane to haemolytic agents. The results showed that incorporation of quercetin into the erythrocyte membranes caused the changes of the partition coefficient of the Tempo spin label between the water and polar head group phases. In the studies, the W/S ratio has been used as a monitor of changes in protein conformation and in the environment within the membrane. It was observed that quercetin caused an increase in protein-protein interactions in human erythrocyte membranes. Haemolytic action of quercetin in the dark was also investigated. This compound showed protective effect against hypotonic haemolysis. However, in the heat-induced haemolysis quercetin caused acceleration of haemolysis. Dark reaction of erythrocyte with quercetin resulted in a shrinkage of the cells and alteration of their shapes. From the results we have concluded that modification of erythrocyte membrane by quercetin proceeds via reaction with membrane lipids and proteins. (C) 2003 Elsevier Inc. All rights reserved.

  97. Man, K. L. Zdyb, R. Huang, S. F. Leung, T. C. Chan, C. T. Bauer, E. Altman, M. S., Growth morphology, structure, and magnetism of ultrathin Co films on W(111), Physical Review B, 67(18), 2003, art. no.-184402

    Abstract:
    The growth morphology, structure, and magnetism of ultrathin Co films on the W(111) surface are studied with conventional and spin polarized low energy electron microscopy and diffraction and first principles total energy calculations. Pseudo-layer- by-layer growth of thick pseudomorphic (ps) Co films is observed at 380 K, while Stranski-Krastanov growth and transformation to a (6x6) closed-packed structure are observed at higher temperatures. On the basis of the calculations, only one ps Co monolayer is expected to be thermodynamically stable against three-dimensional island formation. Calculations also indicate that the magnetic moment on Co atoms at the interface is reduced due to strong hybridization with the substrate, but remains non-zero even for the single ps monolayer. Metastable ps Co/W(111) is found experimentally to be ferromagnetically ordered at 380 K when film thickness exceeds 7.6 ps ML. Although only in-plane magnetization is observed, substrate atomic steps have a strong influence on the magnetization easy axis and magnetic domain structure, which suggests that the in- plane magnetocrystalline anisotropy is weak.

  98. Zdyb, R. Bauer, E., Magnetic domain structure and spin-reorientation transition in ultrathin Fe-Co alloy films, Physical Review B, 67(13), 2003, art. no.-134420

    Abstract:
    The evolution of the magnetic domain structure with the thickness of Fe1-xCox alloy films deposited at room temperature on epitaxial Au(111) films is studied for xless than or equal to0.3 by spin-polarized low-energy electron microscopy. In contrast to pure Fe films that show no out-of-plane magnetization small amounts of Co are sufficient to induce strong perpendicular magnetization below three monolayers with a pronounced striped domain structure. A reorientation transition to in-plane magnetization is found.

  99. Jartych, E. Jalochowski, M. Budzynski, M., Influence of the electrodeposition parameters on surface morphology and local magnetic properties of thin iron layers, Applied Surface Science, 193(1-4), 2002, 210-216

    Abstract:
    Iron layers with thickness of 70-200 nm were prepared by electrodeposition on the polycrystalline Cu substrate at different parameters of the electrolysis. The surface morphology of the iron layers and their local magnetic properties were studied using scanning tunneling microscopy (STM) and conversion electron Mossbauer spectroscopy (CEMS). STM studies revealed the granular structure of the surface of the electrodeposited iron layers with the roughness depending on the temperature of the bath, pH value and the current density. The influence of these electrodeposition parameters on the thickness of the iron layers became manifest in their magnetic anisotropy, as seen by CEMS. (C) 2002 Elsevier Science B.V. All rights reserved.

  100. Jalochowski, M. Strozak, M. Zdyb, R., Anomalous optical absorption in ultrathin Pb films, Physical Review B, 66(20), 2002, art. no.-205417

    Abstract:
    Ultrathin Pb films on Si(111)-(6x6)-Au deposited at 100 K are investigated by scanning tunneling microscopy, reflection high energy electron diffraction, and optical reflectance methods. From the reflectance data for light with a photon energy from 0.5 to 3 eV, the imaginary part of the Pb dielectric function epsilon(Pb) is determined. For films with a thickness of 12 ML, the Pb epsilon(Pb) vs photon energy resembles that expected for a bulk material. At smaller coverages the absorption spectrum shows anomalous, sharp optical structures. These structures are identified as strongly enchanced optical transitions characteristic of bulk materials. Simultaneously, a reduction of the free-electron Drude absorption is observed. This phenomenon is explained in terms of reduced electron screening. Our findings supply evidence of a bulklike electron band structure in ultrathin films and nanoparticles of Pb deposited on Si(111)-(6x6)Au.

  101. Mazurek, P. Jalochowski, M., Ordering of the vicinal Si(1510) surface at low Au coverage, Optica Applicata, 32(3), 2002, 247-252

    Abstract:
    Reflection high-energy electron diffraction (RHEED) and scanning tunnelling microscopy (STM) are used to investigate the ordering process of vicinal silicon surface. A vicinal Si(15 1 0) sample was cut from a Si(001) monocrystal and oriented by X-ray diffractometry techniques. At Au coverage within 1-2 ML and after the subsequent annealing at about 1000 K in UHV conditions this surface exhibits a rectangular imbricate step/terrace structure. The best surface ordering was found at 1.5-2 ML Au coverage where flat Si(001) terraces show 5x3.2 surface reconstruction. The edges of these rectangular terraces are parallel to the [011] and [01 (1) over bar] direction. Due to high density of corners formed by the rectangular terraces, this surface may be suitable for nucleation of quasi zero-dimensional structures.

  102. Jalochowski, M. Strozak, M., Optical anisotropy of Pb nanowires on Si(533) surface, Optica Applicata, 32(3), 2002, 373-379

    Abstract:
    Ultrathin Pb films on Si(533)/Au surface deposited at low temperatures are investigated by STM, RHEED, and by optical reflectance difference spectroscopy (RDS). In particular, we report the observation by RDS of an anisotropy in the optical reflectance of the Si(533) surface covered by Pb nanowires. It is found that the optical anisotropy originates from anisotropy of electrical conductivity of the Si(533) substrate and the anisotropy of Pb nanowires formed on this surface.

  103. Krawiec, M. Wysokinski, K. I., Nonequilibrium Kondo effect in asymmetrically coupled quantum dots, Physical Review B, 66(16), 2002, art. no.-165408

    Abstract:
    A quantum dot asymmetrically coupled to external leads has been analyzed theoretically by means of the equation-of-motion technique and the noncrossing approximation. The system has been described by the single-impurity Anderson model. To calculate the conductance across the device the nonequilibrium Green's function technique has been used. The obtained results show the importance of the asymmetry of the coupling for the appearance of the Kondo peak at nonzero voltages and qualitatively explain recent experiments.

  104. Kwapinski, T. Taranko, R. Taranko, E., Band structure effects in time-dependent electron transport through the quantum dot, Physical Review B, 66(3), 2002, art. no.-035315

    Abstract:
    The evolution operator method is used to study the electron tunneling through the quantum dot. The external microwaves fields are applied to both the dot and leads. Under the adiabatic approximation, the formulas for the time-dependent quantum dot charge and current flowing through the quantum dot are obtained. The time-averaged quantum dot charge, tunneling current, and derivatives of the time-averaged tunneling current with respect to the source drain and gate voltages are calculated beyond the wide band limit for the two-dimensional tight-binding spectrum of the leads electrons. The influence of the singularities of the lead density of states on the photon- assisted tunneling peaks is also discussed.

  105. Sujak, A. Mazurek, P. Gruszecki, W. I., Xanthophyll pigments lutein and zeaxanthin in lipid multibilayers formed with dimyristoylphosphatidylcholine, Journal of Photochemistry and Photobiology B-Biology, 68(1), 2002, 39-44

    Abstract:
    This paper reports the research on the effect of two main carotenoid pigments present in the membranes of macula lutea of the vision apparatus of primates, including humans, lutein and zeaxanthin, on the structure of model membranes formed with dimyristoylphosphatidylcholine (DMPC). The effects observed in DMPC are compared to the effects observed in the membranes formed with other phosphatidylcholines (PC): egg yolk PC (EYPC), and dipalmitoyl-PC (DPPC). The analysis has been focused, in particular, on the following aspects of the organization of lipid-carotenoid membranes: aggregation state of pigments, an effect on a thickness of the bilayer and pigment orientation within the membranes. These problems have been addressed with the application of UV-Vis absorption spectroscopy, linear dichroism measurements and the diffractometric technique. (1) Both lutein and zeaxanthin appear in a partially aggregated form in the oriented DMPC multibilayers, even at molar fractions as low as 2 mol.% with respect to lipid. (2) Orientation of the transition dipole of both xanthophylls with respect to the axis normal to the plane of DMPC membrane is different in the case of a monomeric form (34+/-3degrees in the case of lutein and 26+/-3degrees in the case of zeaxanthin) but essentially the same in the case of aggregated forms of both pigments (42+/-3degrees in the case of utein and 40+/-5degrees in the case of zeaxanthin). It was found that only lutein has an effect on the increase in the thickness of the DMPC membranes (by about 3 Angstrom at 25 degreesC). A similar effect was observed also in the case of DPPC at the same temperatures despite the differences in the physical state of both membrane systems. The differences between the effects of lutein and zeaxanthin observed are interpreted in terms of differences of stereochemical structure of both xanthophylls leading to the different localization in the lipid phase. The results demonstrate significant differences in the behavior of lutein and zeaxanthin in model membranes, which may contribute to their different physiological functions and different efficacy as membrane antioxidants. (C) 2002 Elsevier Science BY. All rights reserved.

  106. Mazurek, P. Daniluk, A. Paprocki, K., Forming the high quality CoSi2 by solid phase epitaxy, Optica Applicata, 32(3), 2002, 389-395

    Abstract:
    Thin films of CoSi2 were grown on Si(111) by solid phase epitaxy (template technique) in UHV condition. We present a practical experimental procedure for the preparation of thin epitaxial films of cobalt silicide. Layers obtained by the deposition of metal on silicon (111) demonstrate a high-quality crystallographic structure. The state of the surface of growing layers is studied with the in situ combination of reflection high-energy electron diffraction (RHEED) azimuthal plots and rocking curve.

  107. Paradowski, M. L. Misiak, L. E., Gd3+ spin-phonon interactions in rare-earth fluoride crystals, Acta Physica Polonica A, 102(3), 2002, 373-384

    Abstract:
    The X-band EPR study of Gd3+-doped LaF3, La0.9Ce0.1F3, La0.9Nd0.1F3, LiYF4 and LiY0.9Yb0.1F4 single crystals in the temperature range 4.2-295 K was carried out in order to investigate the Gd3+ spin-phonon interactions. Spin-Hamiltonian parameters are analysed in the light of the superposition model and the rotational invariance theory for phonon-induced contributions to spin-Hamiltonian parameters. The 4f(7) electron-phonon interactions can be described by the Debye model. It is suggested, from the rotational invariance mechanism for phonon-induced contributions to spin-Hamiltonian parameters, that the rotational contributions are much smaller than those from the strain. Temperature-induced distortions of the crystal field, as well as these distortions caused by the La3+/Nd3+ and Y3+/Yb3+ substitutions, influence significantly the 4f(7) electron-phonon interactions. The coupling constant K-2 of 4f(7) electrons to the whole phonon spectrum of the crystal lattice is stronger in the LaF3, La0.9Ce0.1F3, La0.9Nd0.1F3 with larger temperature-induced distortion of the Gd3+ site symmetry than in LiYF4, LiY0.9 Yb0.1F4. Our results are compared with those for Gd3+-doped RbCdF3 and PbF2 single crystals.

  108. Zdyb, R. Bauer, E., Spin-dependent quantum size effects in the electron reflectivity of ultrathin ferromagnetic crystals, Surface Review and Letters, 9(3-4), 2002, 1485-1491

    Abstract:
    We have studied the spin-dependent quantum size effects in the reflection of 0-20 eV electrons from 2-10-ML-thick Fe microcrystals grown in situ on a W(110) surface in a spin- polarized low energy electron microscope. The goal is to obtain a better understanding of the magnetic ( "asymmetry") image contrast and of the limits of spin polarization devices based on the quantum size contrast. The contrast is interpreted in terms of the band structure and, of the spin-dependent inelastic mean free path. For the figure of merit of spin polarization devices, an upper limit of 5 x 10(-2) is obtained.

  109. Zdyb, R. Bauer, E., Spin-resolved unoccupied electronic band structure from quantum size oscillations in the reflectivity of slow electrons from ultrathin ferromagnetic crystals, Physical Review Letters, 88(16), 2002, art. no.-166403

    Abstract:
    The spin-dependent reflectivity of electrons with energies between 0 and 20 eV from Fe single crystals 2-8 monolayers thick on a W(110) surface is studied by spin-polarized low energy electron microscopy. The quantum size oscillations in the reflectivity are analyzed in a similar manner as in photoemission of ground state electrons, yielding the spin- resolved unoccupied state band structure of Fe in the GammaN direction in the energy range studied.

  110. Yasue, T. Koshikawa, T. Jalochowski, M. Bauer, E., LEEM observation of formation of Cu nano-islands on Si(111) surface by hydrogen termination, Surface Science, 493(1-3), 2001, 381-388

    Abstract:
    The growth of Cu on Si(1 1 1) surface with and without hydrogen termination was studied with low energy electron microscopy. On the clean surface the two-dimensional "5 x 5 " incommensurate layer is first formed followed by the formation of three- dimensional (3D) islands. On the hydrogen-terminated surface the formation of the "5 x 5 " structure is suppressed and nano- scale 3D islands decorate the steps and domain boundaries of the delta7 x 7 structure. Many LEED spots from the nano-islands move with electron energy, which indicates that the islands are faceted. From the analysis of the LEED pattern it is suggested that the nano-islands are the (1 1 1)-oriented beta -phase Cu- Si alloy and are terminated by (1 1 1), {5 5 4} and {15 16 13} faces. (C) 2001 Elsevier Science B.V. All rights reserved.

  111. Jartych, E. Chocyk, D. Budzynski, A. Jalochowski, M., Surface morphology and local magnetic properties of electrodeposited thin iron layers, Applied Surface Science, 180(3-4), 2001, 246-254

    Abstract:
    Thin iron layers with different thickness were prepared by electrodeposition on the polycrystalline substrate. The surface morphology of the layers, their structure and local magnetic properties were studied using scanning tunneling microscopy (STM), X-ray diffraction (XRD) and conversion electron Mossbauer spectroscopy (CEMS). STM studies revealed the granular structure of the surface of the electrodeposited iron layers with the roughness up to 10 nm. XRD analysis proved that these layers were highly strained. The CEMS spectra showed an in-plane magnetic anisotropy in the iron layers. Isomer shift of the electrodeposited iron was different than that of the alpha -Fe. This difference was attributed to the internal stresses existing in the electrodeposited layers. (C) 2001 Elsevier Science B.V. All rights reserved.

  112. Jalochowski, M. Bauer, E., Self-assembled parallel mesoscopic Pb-wires on Au-modified Si(533) substrates, Progress in Surface Science, 67(1-8), 2001, 79-97

    Abstract:
    Arrays of extremely long and perfectly parallel mesoscopic Pb- wires are formed and studied in UHV conditions. Au-modified Si(5 3 3) substrate modified by deposition of sub-monolayer amount of Au are used as templates. A uniform distribution of monoatomic steps and terraces on well-oriented Si(5 3 3) is induced by formation of Au-chains running along step edges. Realtime surface imaging with LEEM shows that the wires growing on substrates held at temperatures close to the room temperature are all aligned parallel to [0 1 (1) over bar] azimuth, along the step edges. After nucleation of elongated islands, the I ML thick wetting layer remains on the vicinal Si surface. RHEED and low-temperature STM experiments show that the wires have triangular cross-section, limited by (1 1 1) and (1 0 0) facets of Pb. The width of the wires is 60 nm, whereas their length is up to 8 mum. The observed growth anisotropy leading to the formation of mesoscopic wires is attributed to enhanced one-dimensional diffusion along the parallel grooves and trenches that form vicinal surfaces. An additional factor, contributing to the anisotropic growth, is probably the anisotropic strain. due to the large misfit between Pb and Si lattices. (C) 2001 Elsevier Science Ltd. All rights reserved.

  113. Zdyb, R. Strozak, M. Jalochowski, M., Gold-induced faceting on Si(533) surface studied by RHEED, Vacuum, 63(1-2), 2001, 107-112

    Abstract:
    Reflection high energy electron diffraction (RHEED) technique was used to study the Si(5 3 3) surface. On the samples cut 14.42 degrees off the (1 1 1) plane in the [2 (1) over bar (1) over bar] direction, a submonolayer of Au up to 0.628 monolayer (ML) was deposited. Bare Si(5 3 3) surfaces after cleaning in ultrahigh vacuum conditions by short flashing up to about 1500 K did not show a long range older on the macroscopic scale. Upon increasing the coverage of Au, the surface transformed gradually into a flat and perfectly ordered Si(5 3 3) plane at a coverage equal to 0.275 ML, and split into a hill-and-valley structure consisting of (1 1 1) and (1 1 5 5) facets at 0.50 ML of Au, and a combination of (1 1 1) and (3 1 1) facets at 0.628 ML of Au. The crucial role of single atom chains of Au formed on the (1 1 1) terraces is experimentally verified and discussed. It was shown that these chains stabilize the facets and allow the creation of a large macroscopic Si(5 3 3) plane. We suggest that this mechanism can also be operative in the case of Si(1 1 5 5) and Si(3 1 1) planes. (C) 2001 Elsevier Science Ltd. All rights reserved.

  114. Jalochowski, M. Bauer, E., Growth of metallic nanowires on anisotropic Si substrates : Pb on vicinal Si(001), Si(755), Si(533), and Si(110), Surface Science, 480(3), 2001, 109-117

    Abstract:
    The spontaneous formation of mesoscopic Pb-wires, on 4 degrees off-cut Si(0 0 1) vicinal surface, Si(7 5 5), Si(5 3 3), and Si(1 1 0) substrates was studied by low-energy electron microscopy. Before the deposition of Pb the substrates were modified by predeposition of a submonolayer amount of Au followed by annealing. The Au-induced reconstruction creates quasi-one-dimensional facets and superstructures. Their width ranged from several hundred nm in the case of the vicinal Si(0 0 1) down to atomic scale size, for the Si(1 1 0) surface. The best-developed arrays of parallel aligned mesoscopic wires were obtained during the deposition of Pb on substrates cooled slightly below room temperature. Wires with length to width ratio reaching 130 were produced on the Si(7 5 5) and the Si(5 3 3) substrates. The width of these nanowires was uniform over the whole substrate and was about 60 nm. The driving forces for the formation of the mesoscopic wires are the anisotropic strain due to the large misfit between the Pb and the Si lattice and one-dimensional diffusion of Pb. (C) 2001 Elsevier Science B.V. All rights reserved.

  115. Yasue, T. Koshikawa, T. Jalochowski, M. Bauer, E., Dynamic observations of the formation of thin Cu layers on clean and hydrogen-terminated Si(111) surfaces, Surface Science, 480(3), 2001, 118-127

    Abstract:
    The growth of Cu on the clean and hydrogen-terminated Si(1 1 1) surfaces is studied in situ by low-energy electron microscopy (LEEM). The dependence of the growth of the "5 x 5" layer on the clean Si(1 1 1) 7 x 7 surface upon the deposition temperature is investigated by combining LEEM with LEED. After completion of the "5 x 5" layer not only the regular-shaped three-dimensional islands reported before are observed but also irregular shaped more two-dimensional islands. On the hydrogen- terminated Si(1 1 1) surface the formation of the "5 x 5" structure is suppressed and nano-scale islands form preferentially at the step edges and domain boundaries. This is attributed to the enhancement of the surface migration of Cu atoms by the elimination of the surface dangling bonds. (C) 2001 Elsevier Science B.V. All rights reserved.

  116. Kwapinski, T. Taranko, R. Taranko, E., Time-dependent transport through a quantum dot: Mean-field, treatment of the Coulomb interaction, Acta Physica Polonica A, 99(2), 2001, 293-305

    Abstract:
    We study an electron transport through a quantum dot in the presence of time-dependent fields. The dot is described by a single level and the intra-dot Coulomb interaction is introduced within the Hartree-Fock approximation. The external fields cause a time-dependent shift of the energy spectrum of the leads and quantum dot. We take into account the spin- polarized solutions for the quantum dot charge. We calculated the time dependence of the current and charge accumulated on the dot, the average current and charge vs. the source-drain and gate voltages in dependence on the Coulomb interaction strength. and the frequencies and amplitude of the external fields.

  117. Misiak, L. E., Gd3+-Yb3+ exchange interactions in LiY1-xYbxF4 single crystals, in Growth, Characterization, and Applications of Single Crystals, Proceedings of SPIE, 4412(), 2001, 177-180

    Abstract:
    The evaluated Gd3+ -Yb3+ exchange interactions over the nearest and the next-nearest neighbors in LiYbxY1-xF4 are found to increase in parabolic manner with x, the concentration of Yb3+ ions. The Gd3+ -Yb3+ exchange interactions are sensitive to x in the range x = 0.6 - 1.0, while they are almost constant in the range x = 0.1 - 0.5. The estimated Gd3+-Yb3+ exchange interaction constants (J = Jnn + Jnnn) are in the range 0.5 - 2.8 GHz for x from 0.1 to 1, respectively. These exchange interaction constants are increased with lowering temperature. The results are comparable to those of estimated using the molecular-field model. The average Gd3+ -Yb3+ pair exchange interaction constant is determined to be 0.33 GHz in paramagnetically diluted LiYbxY1-xF4 crystals.

  118. Paradowski, M. L. Misiak, L. E. Korczak, W. Korczak, S. Z., Gd3+-Yb3+ exchange interactions in LiY1-xYbxF4 single crystals, in Growth, Characterization, and Applications of Single Crystals, Proceedings of SPIE, 4412(), 2001, 242-245

    Abstract:
    The mixed LaxRE1-xF3 (RE = Ce, Pr, Nd) single crystals doped with Gd3+ (0.1 mol%) were grown by a modified Bridgmann-Stockbarger method. The crystal field was investigated using electron paramagnetic resonance technique. The angular dependencies of Gd3+ (8S7/2, f7) line positions with magnetic field oriented in (001) plane were measured in the temperature range 4.2 - 295 K. The surroundings of Gd3+ ions were investigated analyzing spin-hamiltonian parameters in the light of the superposition model. The small distortion of the D43d trigonal symmetry has been observed in LaF3, La0.9Ce0.1F3 and La0.9Nd0.1F3 below 150 K. The local structure deformation of the site symmetry of Gd3+ ions induced by temperature starts at about 150 K becoming larger at 4.2 K. In PrF3 the distortion was not observed in the temperature range 4.2 - 295 K. The results were compared with those of Gd3+-doped LiYF4 crystals.

  119. Duden, T. Zdyb, R. Altman, M. S. Bauer, E., Micromagnetic and microcrystalline structure of ultrathin Co layers on W single crystal surfaces, Surface Science, 480(3), 2001, 145-152

    Abstract:
    The magnetic domain structure and the microcrystalline structure of ultrathin Co layers on W(1 1 0), W(1 0 0) and W(1 1 1) surfaces are studied with low energy electron microscopy with and without spin-polarization with the goal to shed some light on the importance of the various parameters which determine the micromagnetic structure. (C) 2001 Elsevier Science B.V. All rights reserved.

  120. Podleśny, J. Misiak, L. Koper, R., Concentration of free radicals in faba bean seeds after the pre-sowing treatment of the seeds with laser light, International Agrophysics, 15(), 2001, 185-189

    Abstract:
    Experiments were conducted at the Institute of Soil Science and Plant Cultivation in Puławy, the Agricultural University and University of Maria Curie-Skłodowska in Lublin. The first row factor were three morphologically differentiated white lupine varieties: Nadwiślański (traditional form) and Tim (determinated form), and the second one - doses of laser irradia­tion: D0 - without irradiation, D1 - single fold irradiation, D2 -double irradiation, D3 - three fold irradiation, D4 - four fold irradiation, D5 - five fold irradiation. Single exposition was equal to 4·10-3 J cm-2s-1. Irradiation of double have been carried out at the Physics Department of the Agricultural University in Lublin, using a device for the laser irradiation of seed prior to sowing. The irradiated seeds of both faba bean forms gave a faster uptake of water and achieved a larger mass during seed imbibing in com­parison to seeds without irradiation. It was found that the earlier and steadier emergence of these plants was a consequence of this process. Faba bean seedlings which were grown from irradiated seeds achieved, in the succeeding measurement dates, significantly larger coleoptile and root length in comparison to those seedlings which had not been so irradiated by laser light. A significant incre­ase was observed in the concentration of free radicals in those seeds which were treated, before sowing, with laser light. The largest increase in the number of free radicals in the seed of both faba bean varieties was found after three and four fold seed irradiation. There was no significant effect of examined varieties in seed irradiation on free radical concentration in the young faba bean plant organs. The number of free radicals in the leaves, stems and roots did not differ significantly from that found in the particular organs of plant grown from non-irradiated seeds. Laboratory research did not show any increase in the number of free radicals in seeds harvested from plants grown from irradiated seeds.

  121. Koshikawa, T. Yasue, T. Jalochowski, M. Bauer, E., Dynamic LEEM observation of Cu nanostructure formation processes on Si(111) with and without hydrogen, Microbeam Analysis 2000, Proceedings, (), 2000, 259-260

  122. Yasue, T. Koshikawa, T. Jalochowski, M. Bauer, E., Dynamic LEEM observation of Cu nanostructure formation processes on Si(111) with hydrogen, Surface Review and Letters, 7(5-6), 2000, 595-599

    Abstract:
    Dynamic observation of the growth of Cu on dean and hydrogen- terminated Si(111) surfaces was carried out by using low energy electron microscopy (LEEM). On the clean surface, the two- dimensional "5 X 5" structure is formed, and the formation process of the "5 x 5" structure depends on the substrate temperature. Triangular islands are grown on the "5 x 5" structure after further deposition of Cu. On the other hand, the nanoscale islands are directly formed on the hydrogen- terminated surface below about 400 degreesC. Above about 400 degreesC, however, the Cu-induced desorption of hydrogen takes place, and the growth process becomes similar to that on the clean surface.

  123. Jalochowski, M., Self-assembled parallel mesoscopic Pb wires on vicinal Si(III), Acta Physica Polonica A, 98(3), 2000, 259-269

    Abstract:
    The work presents a novel method of production of mesoscopic metallic wires on semiconducting surfaces. Making use the self- assembly phenomenon, arrays of extremely long and perfectly parallel mesoscopic Pb-wires on vicinal Si(111) substrates are formed and studied in UHV conditions. Before deposition of Pb a uniform distribution of monoatomic steps and terraces was induced by formation of Au chains running along step edges. The wires growing on the substrates held at temperatures close to the room temperature reach up to 8 mum length. A reflection high electron energy diffraction experiment shows that the wires laying on Si(533) along the step edges have triangular cross-section determined by (111) and (100) facets of Pb. Scanning tunneling microscopy images collected at low temperatures have enabled us to determine details of the wires shape and morphology of the substrate. The width of the wires was approximately equal to 60 nm whereas their height was about 10 nm. The observed strong growth anisotropy is attributed to step edge barriers and high Pb mobility on the smooth Si(111) narrow terraces that form vicinal surfaces and the anisotropic strain due to large misfit between Pb and Si lattices.

  124. Jablonski, M. Korczak, W. Gorzelak, M. Jagiello-Wojtowicz, E., Intermittent three-month treatment with Ukrain in intact and ovariectomized rats. Part III: Effect on the native electron paramagnetic resonance signal intensity of the femur, Drugs under Experimental and Clinical Research, 26(5-6), 2000, 333-336

    Abstract:
    Ukrain, an acid alkaloid derivative of Chelidonium majus L., was administered intraperitoneally to ovariectomized and sexually mature female control rats at doses of 7, 14 and 28 mg/kg once daily for 10 days, followed by a 10-day break. This procedure was repeated five times. At the end of the long-term treatment with Ukrain (24 h after the last dose of the drug) the left femora of the rats were harvested Dried bones were studied by electron paramagnetic resonance (EPR) method Significant changes in the intensity of the native signal were observed within the groups (ANOVA, p = 0.0001); the lowest value was observed in the ovariectomized rats treated with 28 mg/kg of Ukrain (decrease of 40.8% compared to the ovariectomized group, p = 0.005), A significant increase in the intensity of the signal was observed in the intact 7 mg/kg Ukrain-treated group (34.7% compared to controls, p = 0.004).

  125. Paradowski, M. L. Pacyna, A. W. Bombik, A. Korczak, W. Korczak, S. Z., Magnetic susceptibility of LaxCe1-xF3 single crystals, Journal of Magnetism and Magnetic Materials, 212(3), 2000, 381-388

    Abstract:
    The magnetic susceptibility of LaxCe1-xF3 single crystals, for 0 < x less than or equal to 0.5, has been measured from 4 up to 300 K in a magnetic field B approximate to 0.2 T applied parallel to the crystallographic a-axis (perpendicular to the c-axis). The effective Bohr magneton number p(eff) and paramagnetic Curie temperature theta(p) have been obtained, using the Curie-Weiss law in the temperature range 100-300 K. The interconfiguration excited energy E-ex, the spin- fluctuation temperature T-sf, and the g-values, corresponding to three Kramers doublets in the F-2(5/2), ground multiplet of Ce3+ ion in LaxCe1-xF3 have been determined, using quantum theory of paramagnetic susceptibility. The mixed-valent and crystal held effects influence significantly the g-values. The effect of the dilution of the paramagnetic Ce3+ ions with diamagnetic La3+ ions is also discussed. (C) 2000 Elsevier Science B.V. All rights reserved.

  126. Krawiec, M. Wysokinski, K. I., Charge on the quantum dot in the presence of tunneling current, Solid State Communications, 115(3), 2000, 141-144

    Abstract:
    The calculation of the charge present in central region of the double barrier structure at nonequilibrium conditions is discussed. We propose here a simple method to calculate nonequilibrium Green's functions which allows consistent calculations of retarded and distribution functions. To illustrate the approach, we calculate the charge on the quantum dot coupled via tunnel barriers to two external leads having different chemical potentials mu(L) and mu(R). The obtained results have been compared with other approaches existing in the literature. They all agree in the equilibrium situation and the departures grow with increasing the difference mu(L) - mu(R). (C) 2000 Published by Elsevier Science Ltd. All rights reserved.

  127. Krawiec, M. Wysokinski, K. I., Spectral functions of the quantum dot coupled to normal and/or superconducting leads, Acta Physica Polonica A, 97(1), 2000, 197-200

    Abstract:
    We study the spectrum of the quantum dot coupled to two external leads, which may be normal and/or superconducting. The dot is described by the Anderson-Hubbard impurity model in the infinity U limit. The impurity spectral function shows complex behavior depending on the temperature and the state of the leads. For normal leads and at low temperature we observe the appearance of the Kondo resonance, while for BCS-like superconducting leads the bound states emerge due to absence of low energy excitations in the leads.

  128. Mazurek, P. Daniluk, A. Paprocki, K., Analysis of RHEED intensities during formations of the CaF2/Si(111) and MgO/YSi2-x/Si(100) interface, Vacuum, 57(2), 2000, 229-236

    Abstract:
    We have explored the epitaxial growth of two types of insulators on silicon substrate. CaF2 and MgO are able to block silicon diffusion to the growing surface forming stable interfaces type Si-Ca-F and MgO/YSi2-x in molecular beam epitaxy (MBE) deposition process. We are able to establish proper condition of epitaxy for this two insulators by controlling nucleation process during formation of the interfaces in CaF2/Si(1 1 1) and MgO/YSi2-x/Si(1 0 0) systems. High-perfection heteroepitaxy is possible even for early stages of the deposition process. (C) 2000 Elsevier Science Ltd. All rights reserved.

  129. Niedzwiedz, M. Gawron, A. Korczak, W. Trebacz, H., Analysis of some biophysical and biochemical parameters of long bones of spiny mouse (Acomys cahirinus) in its life cycle, Folia Histochemica Et Cytobiologica, 37(2), 1999, 161-162

  130. Krawiec, M. Wysokinski, K. I., Superconductivity in correlated systems: Constraint quantization of slave bosons, Physical Review B, 59(14), 1999, 9500-9507

    Abstract:
    The quantization rules obtained by Le Guillou and Ragoucy in the slave particle theories of correlated systems have been applied to study the superconductivity in extended Hubbard and t-J models. The quantization scheme has the virtue of treating the local constraint exactly. We compare our numerical results with those obtained in the mean-field approximation for usual slave boson technique. We also discuss the relation of the present approach with method of equation of motion for Hubbard operators. Where possible the obtained results are also compared with experimental data on high-temperature superconductors, as in these materials the essential physics is believed to depend on the presence of strong correlations. [S0163-1829(99)11913-1].

  131. Sujak, A. Gabrielska, J. Grudzinski, W. Borc, R. Mazurek, P. Gruszecki, W. I., Lutein and zeaxanthin as protectors of lipid membranes against oxidative damage: The structural aspects, Archives of Biochemistry and Biophysics, 371(2), 1999, 301-307

    Abstract:
    Two main xanthophyll pigments are present in the membranes of macula lutea of the vision apparatus of primates, including humans: lutein and zeaxanthin. Protection against oxidative damage of the lipid matrix and screening against excess radiation are the most likely physiological functions of these xanthophyll pigments in macular membranes, A protective effect of lutein and zeaxanthin against oxidative damage of egg yolk lecithin liposomal membranes induced by exposure to UV radiation and incubation with 2,2'-azobis (2- methypropionamidine) dihydrochloride, a water-soluble peroxidation initiator, was studied. Both lutein and zeaxanthin were found to protect lipid membranes against free radical attack with almost the same efficacy. The W-induced lipid oxidation was also slowed down by lutein and zeaxanthin to a very similar rate in the initial stage of the experiments (5-15 min illumination) but zeaxanthin appeared to be a better photoprotector during the prolonged UV exposure, The decrease in time of a protective efficacy of lutein was attributed to the photooxidation of the carotenoid itself. Both lutein and zeaxanthin were found to slightly modify mechanical properties of the liposomes in a very similar fashion as concluded on the basis of H-1 NMR and diffractometric measurements of pure egg yolk membranes and membranes pigmented with the xanthophylls. Linear dichroism analysis of the mean orientation of the dipole transition moment of the xanthophylls incorporated to the lipid multibilayers revealed essentially different orientation of zeaxanthin and lutein in the membranes, Zeaxanthin was found to adopt roughly vertical orientation with respect to the plane of the membrane. The relatively large orientation angle between the transition dipole and the axis normal to the plane of the membrane found in the case of lutein (6 degrees in the case of 2 mol% lutein in EYPC membranes) was interpreted as a representation of the existence of two orthogonally oriented pools of lutein, one following the orientation of zeaxanthin and the second parallel with respect to the plane of the membrane, The differences in the protective efficacy of lutein and zeaxanthin in lipid membranes were attributed to a different organization of zeaxanthin-lipid and lutein-lipid membranes. (C) 1999 Academic Press.

  132. Paradowski, M. L. Misiak, L. E., EPR of Gd3+-doped La0.9Nd0.1F3 crystal: Spin-phonon interactions and spin-lattice relaxations, Acta Physica Polonica A, 95(3), 1999, 367-380

    Abstract:
    The X-band EPR study of Gd3+-doped La0.9Nd0.1F3 single crystal in the temperature range 4.2-295 K is carried out in order to investigate crystal field effects, the Gd3+ spin-phonon interactions, as well as Gd3+ and Nd3+ spin-lattice relaxation times. The local distortions at 4.2 K of the positions of the eight F- ions surrounding the Gd3+ ion in the La0.9Nd0.1F3 crystal were determined from comparison of the theoretical with the experimental spin-Hamiltonian parameters. The spin-phonon interactions can be described by the Einstein model, which better characterizes the behavior of paramagnetic centers in LaF3 and La0.9Nd0.1F3 crystals than the Debye model. It is suggested, from the rotational invariance mechanism for phonon- induced contributions to spin Hamiltonian parameters, that the rotational contributions are much smaller than those from the strain.

  133. Paradowski, M. L. Korczak, W. Misiak, L. E. Korczak, Z., Growth and investigation of LaxRE1-xF3 (RE = Ce, Pr, Nd) single crystals, in Solid State Crystals: Single Crystal Growth, Characterization, and Applications, Proceedings of SPIE, 3724(), 1999, 47-51

    Abstract:
    The mixed LaxRE1-xF3 (RE = Ce, Pr, Nd) single crystals doped with Gd3+ (0.1 mol%) were grown by a modified Bridgmann-Stockbarger method using an induction furnace. The quality of crystals were controlled by X-ray diffraction and EPR technique, in addition the observation of defects with the polarizing microscope after chemical etching with acid was performed. The behavior of surrounding Gd3+ ions in hexagonal matrices was investigated at different temperatures (4.2-300 K), analyzing EPR data in the light of the superposition model. The distortion of the site symmetry of Gd3+ ions from the C2v towards C2 was observed in La0.9 Nd0.1F3 at 4.2 K. The low temperature magnetic ordering was determined to be antiferromagnetic (TN = 0.4 K for NdF3 and TN = 0.03 K for La0.9Nd0.1F3 using the molecular field theory).

  134. Krawiec, M. Domanski, T. Wysokinski, K. I., Do Van Hove singularities in leads influence tunneling current through quantum dot?, Acta Physica Polonica A, 94(3), 1998, 411-414

    Abstract:
    Using the Landauer type formula for the current through quantum dot we have studied the influence of the singularities in the density of states in leads on the differential conductance of the system and answered affirmatively the above question. The presence of Van Rove singularities in the leads may induce an additional structure on the conductance vs. voltage curve. The dot itself has been described by the single impurity Anderson model with a very strong "on-dot" Coulomb repulsion. We also simulate the effect of electron-phonon interaction in the dot by allowing for the fluctuations of the "impurity" energy level.

  135. Daniluk, A. Mazurek, P. Paprocki, K. Mikolajczak, P., RHEED intensity oscillations observed during the growth of CaF2 on Si(111), Physical Review B, 57(19), 1998, 12443-12447

    Abstract:
    Analyses of reflection high-energy electron diffraction (RHEED) intensity changes observed during initial stages of heteroepitaxial growth of calcium fluoride (CaF2) on Si(111) are presented. Layers obtained by deposition of CaF2 on a hot (550 degrees C) substrate demonstrate a high-quality crystallographic structure. The state of the surfaces of growing layers is studied with the in situ combination of RHEED azimuthal plots and rocking curve. The intensity of the reflected beam is calculated by solving the one-dimensional Schrodinger equation.

  136. Jalochowski, M. Strozak, M. Zdyb, R., One-dimensional structures on Si(111) observed by RHEED, Thin Solid Films, 306(2), 1997, 224-227

    Abstract:
    A vicinal Si(111) surface covered with a sub-monolayer amount of Au has been studied by reflection high energy electron diffraction (RHEED). At the coverage equal to 0.20 ML of Au, the RHEED pattern showed a reconstruction in the form of regularly distributed monoatomic steps. In order to determine the shape of the surface unit cell, several RHEED patterns obtained within a wide range of the electron incident angle were recorded and analyzed. The surface was composed of flat Si(111) terraces separated by single Si(111) steps. This surface was identified as an ideal Si(755) facet with Au atoms that form quasi-one-dimensional chains running along a Si[1(1) over bar0$] azimuth. Regularly spaced steps were stable within the investigated range of temperatures from 100 to 470 K. (C) 1997 Elsevier Science S.A.

  137. Jalochowski, M. Strozak, M. Zdyb, R., Gold-induced ordering on vicinal Si(111), Surface Science, 375(2-3), 1997, 203-209

    Abstract:
    A vicinal Si(111) surface covered with a sub-monolayer amount of Au has been studied by RHEED. For a sample misoriented by 8.46 degrees towards the [(1) over bar (1) over bar 2] azimuthal direction at a coverage equal to 0.20 ML of Au, the RHEED pattern showed a regular distribution of monoatomic steps with the staircase width equal to 18.88+/-0.33 Angstrom. Au- induced order was identified with a (755) facet of Si. Regularly spaced steps were stable within the investigated range of temperatures from 130 to 470 K. Upon further increase of the Au-coverage the periodicity was disturbed and al a coverage of about 0.50 ML of Au onset of (root 3 x root)R30 degrees reconstruction was visible. (C) 1997 Elsevier Science B.V.

  138. Jalochowski, M. Strozak, M. Zdyb, R., Gold-induced one-dimensional ordering on vicinal Si(111), Vacuum, 48(3-4), 1997, 273-275

    Abstract:
    Behaviour of a sub-monolayer Au-coverage on the vicinal Si(111) has been studied by RHEED. For the sample misoriented by 8.46 degrees towards the [<(11)over bar 2>] azimuthal direction at the coverage equal to 0.20 ML of Au, the RHEED pattern showed almost perfect distribution of the monoatomic Si(111) steps with the staircase width equal to 18.52 +/- 0.66 Angstrom. Au- induced order was identified with the (755) facet of Si with a one-dimensional chains of Au. Upon further increase of the Au deposition this regular distribution was gradually disturbed and at the coverage of about 0.50 ML of Au onset of an (root 3 x root 3)R 30 degrees reconstruction was visible. (C) 1997 Elsevier Science Ltd.

  139. Paradowski, M. L. Pacyna, A. W. Bombik, A. Korczak, W. Korczak, S. Z., Magnetic susceptibility of LaxNd1-xF3 single crystals, Journal of Magnetism and Magnetic Materials, 166(1-2), 1997, 231-236

    Abstract:
    The ac susceptibility of LaxNd1-xF3 single crystals, for 0 less than or equal to x less than or equal to 0.1, has been measured from 1.5 up to 40 K and their de susceptibility for 0 less than or equal to x less than or equal to 1 has been measured from 3 up to 300 K in magnetic fields up to 0.2 T. In both susceptibilities the magnetic fields were applied parallel to the crystallographic a-axis (perpendicular to the c-axis). The effective Bohr magneton number p(eff) and paramagnetic Curie temperature theta(p) have been obtained, using the Curie-Weiss law in the temperature range 100-300 K. Also the g-values corresponding to the five Kramers doublets in the I-4(9/2), ground multiplet of Nd3+ ion in LaxNd1-xF3 have been determined in the direction perpendicular to the c-axis, using the Van Vleck theory of paramagnetic susceptibility. The effect of the dilution of the paramagnetic Nd3+ ions with diamagnetic La3+ ions is also discussed.

  140. Daniluk, A. Mazurek, P. Paprocki, K. Mikolajczak, P., Monte-Carlo simulation of Ge on Si(111) MBE growth: analysis of percolative structure, Thin Solid Films, 306(2), 1997, 220-223

    Abstract:
    Reflection high energy electron diffraction (RHEED) intensity oscillations were observed during molecular beam epitaxy (MBE) growth of Ge on Si(111) surface. At 250 degrees C the oscillations continue up to 6 monolayers. The intensity of the reflected beam is calculated by solving the one-dimensional Schrodinger equation. Monte-Carlo simulation was used for the growth simulation in order to investigate fundamental behaviours of reflectivity chan during the Stranski-Krastanov growth of Ge on the Si(111) surface at 250 degrees C. (C) 1997 Elsevier Science S.A.

  141. Daniluk, A. Mazurek, P. Paprocki, K. Mikolajczak, P., Distributed growth model used for the interpretation of RHEED intensity oscillations observed during the growth of Pb on Si(111) substrates, Thin Solid Films, 306(2), 1997, 228-230

    Abstract:
    Analyses of reflection high-energy electron diffraction (RHEED) intensity changes observed during initial stages of heteroepitaxial growth of Pb on Si(111) substrates were presented. The intensity of the reflected beam is calculated by solving the one-dimensional Schrodinger equation. A simple birth-death model was used for the growth simulation in order to investigate the fundamental behaviours of reflectivity change during the growth of Pb on the Si(111) surface. (C) 1997 Elsevier Science S.A.

  142. Daniluk, A. Mazurek, P. Paprocki, K. Mikolajczak, P., RHEED intensity oscillations observed during the growth of YSi2-x on Si(111) substrates, Surface Science, 391(1-3), 1997, 226-236

    Abstract:
    For the first time reflection high-energy electron diffraction intensity oscillations were observed during reactive deposition epitaxy (RDE) growth of YSi2-x (x congruent to 0.3) on the Si(111) surface. The YSi2-x crystallographic structure consists of Y planes alternating with Si planes parallel to the Si(111) substrate planes. The intensity of the reflected beam is calculated by solving the one-dimensional Schrodinger equation. A birth-death model was used for the growth simulation in order to investigate fundamental behaviours of reflectivity change during the growth of YSi2-x on the Si(111) surface. (C) 1997 Elsevier Science B.V.

  143. Misra, S. K. Misiak, L. E., EPR study of Gd3+-doped RbR(SO4)(2)center dot 4H(2)O (R=Pr, Nd, Sm, Eu) single crystals: Phase transitions and spin-Hamiltonian parameters, Physical Review B, 56(5), 1997, 2391-2398

    Abstract:
    Extensive EPR measurements were carried out on Gd3+-doped RbR(SO4)(2) . 4H(2)O crystals (R=rare-earth ions, Sm, Eu, Pr, Nd) in the temperature range 100-300 K. The room-temperature data indicate that Gd3+ ions substitute equally for R3+ ions at the two magnetically inequivalent sites in the unit cell, and that the site symmetry of the Gd3+ ion is monoclinic. The Gd3+ room-temperature spin-Hamiltonian parameters and linewidths were estimated. The phase transition temperatures (T-c) were determined to be 175 +/- 1 K (first order) in RbPr(SO4)(2) . 4H(2)O, 178.5+/-1K (first order) in RbNd(SO4)(2) . 4H(2)O, 232+/-0.5K (second order) in RbSm(SO4)(2) . 4H(2)O, and 230.5+/-0.5 K (second order) in RbEu(SO4)(2) . 4H(2)O. In RbPr(SO4)(2) . 4H(2)O and RbNd(SO4)(2) . 4H(2)O, the occurrence of the first-order phase transitions was deduced from abrupt changes in the behavior of the linewidth, zero-field splitting, and line positions, and coexistence of lines observed below and above T-c. In addition, there were observed occurrences of two more phase transitions second order in nature in RbPr(SO4)(2) . 4H(2)O (T-cl = 261 K, T-c2=207.5 K) and in RbNd(SO4)(2) . 4H(2)O (T-cl = 250 K, T-c2= 219.5 K); these were not as sharply defined as the preceding ones. Below T-c, for all the crystals, the symmetry of the crystals was found to be lower than monoclinic, the four ions in the unit cell becoming magnetically inequivalent from each other. The observed second- order phase transitions in the four crystals were found to be in agreement with Landau theory of second-order phase transitions; the critical exponent was determined to be beta congruent to 0.51.

  144. Paradowski, M. L. Misiak, L. E., EPR study of Gd3+ in La0.9Nd0.1F3 single crystal, Nukleonika, 42(2), 1997, 543-550

    Abstract:
    EPR (X-band) study of Gd3+-doped (0.1 mol%) La0.9Nd0.1F3 single crystal at liquid helium, liquid nitrogen and room temperatures has been carried out in order to determine the crystal field effects in the La0.9Nd0.1F3 host, and to estimate the exchange interactions between Gd3+ and Nd3+ ions. Eleven spin-Hamiltonian parameters have been evaluated, by fitting the data from the angular variation of resonance lines in the ZX plane, to the spin-Hamil­tonian for the rhombic C2v symmetry of the crystal field. The average Gd3+ - Nd3+ exchange interaction J (= -2.7 GHz) has been estimated from the molecular-field model using the Gd3+ g-value shift between paramagnetic (Gd3+-doped La0.9Nd0.1F3) and diamagnetic (Gd3+-doped LaF3) crystals at 4.2 K.

  145. Misiak, L. E., On crystal growth of LiYF4, in Solid State Crystals: Growth and Characterization, Proceedings of SPIE, 3178(), 1997, 48-51

    Abstract:
    The Bridgman-Stockbarger method was used to grow single crystals of LiYF4. Smaller LiYF4 crystals can be grown in an induction furnace, whereas the resistance furnace is more useful for bigger crystals growth. The best parameters of crystal growth process were determined. The crystals were investigated by X-ray powder diffraction, the Laue X-ray reflection method and by using polarizing microscope after chemical etching. The best crystals were obtained from the resistance furnace using lowering rate 0.5 mm/h, the temperature gradient 60 °C/cm and the c-axis oriented along the crucible.

  146. Jalochowski, M. Hoffman, M. Bauer, E., Quantized hall effect in ultrathin metallic films, Physical Review Letters, 76(22), 1996, 4227-4229

    Abstract:
    The Hall coefficient R(H) Of ultrathin epitaxial Pb films is determined experimentally. A comparison with electrical conductivity data leads to the conclusion that the investigated Pb layers behave like a size-quantized metal. Pronounced variations of R(H) With the film thickness were found. The observed reversal of the sign of R(H) is discussed within the available theory of the quantum size effect describing the galvanomagnetic properties of metals. We find that the observed phenomenon cannot be explained by the free electron model of a quantized layer.

  147. Daniluk, A. Mazurek, P. Mikolajczak, P., RHEED intensity oscillations observed during growth of Ge on Si(111) substrates, Surface Science, 369(1-3), 1996, 91-98

    Abstract:
    Reflection high-energy electron diffraction (RHEED) intensity oscillations were observed during molecular beam epitaxy growth of Ge on a Si(111) surface. At 250 degrees C the oscillations continue up to 6 ML. When Ge is grown at room temperature on the Ge/Si(111) surface the oscillations continue up to 14 ML. During the growth of Ge thin films on a clean Si(111)-7x7 surface at room temperature the oscillations continue up to 10 ML. The intensity of the reflected beam is calculated by solving the one-dimensional Schrodinger equation. A simple birth-death model was used for the growth simulation in order to investigate fundamental behaviours of reflectivity change during the Stranski-Krastanov growth of Ge on the Si(111) surface at 250 degrees C.

  148. Mitura, Z. Mazurek, P. Paprocki, K. Mikolajczak, P. Beeby, J. L., In situ characterization of epitaxially grown thin layers, Physical Review B, 53(15), 1996, 10200-10208

    Abstract:
    A method of characterization of ultrathin layers based on analysis of reflection high-energy electron diffraction (RHEED) azimuthal plots using dynamical diffraction theory is presented. Dysprosium silicide thin films are grown on a Si(111)-7 x 7 substrate. Layers obtained following deposition of Dy on a hot (600 degrees C) substrate demonstrate a high- quality crystallographic structure. RHEED azimuthal plots collected experimentally for those samples at Bragg reflections show reproducible fine structure. A series of calculations is carried out to analyze the experimental data, and detailed agreement is found between the numerical and measured azimuthal plots. The structure below the surface resembles bulk DySi2-x with alternate planes of Dy and Si, At the surface the structure is terminated with Si atoms which, however, do not form a single plane (as in the bulk) but form two subplanes separated by a distance of about 0.5 Angstrom. It is concluded that analysis of RHEED azimuthal plots can be very useful for simple in situ characterization of growing layers.

  149. Wojtowicz, K. PawlikowskaPawlega, B. Gawron, A. Misiak, L. E. Gruszecki, W. I., Modifying effect of quercetin on the lipid membrane, Folia Histochemica Et Cytobiologica, 34(), 1996, 49-50

  150. Gawron, A. Wójtowicz, K. Misiak L. E., Gruszecki, W. I., Effects of incorporation of lutein and 8-methoxypsoralen into erythrocyte and liposomal membranes, Pharmaceutical Sciences, 2(), 1996, 89-91

    Abstract:
    To determine whether the biological activity of lutein and 8-methoxypsoralen are related to their effect on membrane lipids, their effects, in the dark, on liposomal and erythrocyte membranes were studied by electron paramagnetic resonance (by use of a spin label), by ultrasound absorption, and by differential scanning calorimetry. Incorporation of lutein or 8-methoxypsoralen into erythrocyte membranes increased the fluidity of the membrane in the lipid core adjacent to the hydrophilic zone (as monitored with 5-doxyl-stearic acid spin label). Both compounds also increased ultrasound absorption in dipalmitoylphosphatidylcholine liposomes and reduced the temperature of the main phase transition. These results indicate that despite their different chemical structures and their different localization in the membrane, on a molecular level the mode of action of these two drugs on biomembranes is very similar.

  151. Mitura, Z. Mazurek, P. Paprocki, K. Mikolajczak, P. Maksym, P. A. Beeby, J. L., Structural characterization of thin films with the use of RHEED azimuthal plots, Microscopy of Semiconducting Materials 1995, (), 1995, 541-544

    Abstract:
    A quantitative method of characterizing ultra thin films based on a precise analysis of RHEED azimuthal plots is presented. An interpretation of experimental data collected for dysprosium silicide layers grown on a Si(lll) substrate is carried out. Detailed agreement for experimental azimuthal plots and theoretical ones obtained from a numerical solution of the Schrodinger equation is demonstrated.

  152. Mazurek, P. Paprocki, K. Mikolajczak, P., Epitaxial silicides: New results from RHEED analysis, Thin Solid Films, 267(1-2), 1995, 95-98

    Abstract:
    The growth kinetics and surface structure of Y, Dy and Co silicides are examined using a new reflection high-energy electron diffraction (RHEED) method. We prepared epitaxial silicide films on (111) Si by (1) deposition of metal and contact reaction (solid phase epitaxy), and (2) deposition of metal on hot substrates (reactive deposition). Subsequent annealing at temperatures up to 600 degrees C yielded monocrystalline, continuous layers, whose properties were examined by means of RHEED (in situ) and X-ray diffraction and scanning electron microscopy (ex situ). Method 2 was shown to give better results. We have measured directly the yttrium silicide formation temperature which can be as low as 120 degrees C for thin (60 Angstrom) metal layer deposited on (111)Si substrate. RHEED azimuthal plots of the Si layer which was grown on silicides depends strongly on the crystalline quality of the epitaxial layers. A study of the growth of thin (10-150 Angstrom) silicon overlayers on yttrium, dysprosium and cobalt silicide films epitaxially grown on (111)Si was also made.


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