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  1. 41 Acta Physica Polonica A

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  1. 41 Guziewicz E.

  2. 25 Godlewski M.

  3. 14 Kopalko K.

  4. 13 Witkowski B.

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1
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Reflectivity Study of Hg_{1-x}Co_{x}Se Crystals

100%
Guziewicz E., Kowalski B. J., Orłowski B. A., Szuszkiewicz W.
Acta Physica Polonica A
|
1994
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vol. 86
|
issue 5
875-878
EN
The reflectivity spectra of Hg_{1-x}Co_{x}Se (x = 0.0, 0.024, 0.031) crystals were measured in the vacuum ultraviolet photon energy range from 4 to 12 eV to find the influence of Co ions on the valence band electronic structure of the HgSe crystal. The structure of the reflectivity spectra was interpreted in terms of the electronic band structure of the binary material (HgSe) assuming direct allowed interband transitions.
2
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Content available

Tuning of Color Chromaticity of Light Emission from ZnSe Films Grown on a GaAs Substrate by Atomic Layer Epitaxy

88%
Skrobot M., Godlewski M., Guziewicz E., Kopalko K., Phillips M.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
359-367
EN
Monocrystalline films of sphalerite-type ZnSe were grown on GaAs(100) substrates from elemental Zn and Se precursors by atomic layer epitaxy in a gas flow system. Due to color mixing of band edge and deep defect-related emissions these layers emit intensive white light. Depth profiling cathodoluminescence indicates that green and red emissions mostly come from disordered regions of the films, close to the ZnSe/GaAs interface. We tested a possibility of tuning of chromaticity coordinates and of color temperature of the emission. We found that the chromaticity parameters (color perception) can be tuned by either regulating the appropriate accelerating voltage of electrons or current density of primary electrons in cathodoluminescence investigations. These properties of ZnSe films make them suitable for some practical applications as white light sources.
3
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4f Shell of Gd^{2+} and Gd^{3+} Ions in Sn_{1-x}Gd_{x}Te - Resonant Photoemission Study

88%
Kowalski B. J., Gołacki Z., Guziewicz E., Orłowski B. A., Johnson R. L.
Acta Physica Polonica A
|
1997
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vol. 92
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issue 5
875-878
EN
Resonant photoemission spectra of Sn_{1-x}Gd_{x}Te (x=0.02 and 0.08) measured for the photon energy range 142 to 151 eV show the valence band density of states distribution and the Gd 4f derived maximum. The energy position of the J=0 component of the Gd 4f maximum was determined and used as a measure of the Gd 4f shell binding energy. The electrostatic model of core level shifts was used to interpret the difference in the Gd 4f binding energies observed for x=0.02 and x=0.08.
4
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Cathodoluminescence Measurements at Liquid Helium Temperature of Poly- and Monocrystalline ZnO Films

88%
Witkowski B., Wachnicki Ł., Jakieła R., Guziewicz E., Godlewski M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-28-A-30
EN
Scanning electron microscopy, cathodoluminescence and secondary ion mass spectroscopy investigations are used to study an inter-link between structural quality, elements distribution and light emission properties of ZnO poly- and monocrystalline films grown by the atomic layer deposition. Cathodoluminescence and scanning electron microscopy investigations were performed at liquid helium temperature for four different types of ZnO films deposited on different substrates.
5
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Contribution of Mn 3d Electrons To the Valence Band of Sn_{0.9}Mn_{0.1}te

88%
Nadolny A., Guziewicz E., Kowalski B., Orłowski B., Johnson R.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
454-458
EN
The synchrotron radiation in the energy range between 15 and 70 eV was used to investigate the electronic structure of the crystalline Sn_{0.9}Mn_{0.1}Te by means of the resonant photoemission spectroscopy. Fano-type resonance has been observed in the obtained constant initial energy curves with the resonant energy 50.6 eV and antiresonant energy 49.0 eV. The energy distribution curves taken at photon energies close to the Mn 3p-3d transitions allow us to conclude that Mn atoms contribute to the valence band mainly at energies of 4.0 eV and 7.8 eV below the valence band edge.
6
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Zn(Mn)O Surface Alloy Studied by Synchrotron Radiation Photoemission

88%
Guziewicz E., Kopalko K., Sadowski J., Guziewicz M., Golacki Z.
Acta Physica Polonica A
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2005
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vol. 108
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issue 4
689-696
EN
The Mn/ZnO(0001) system was investigated by synchrotron radiation photoemission. The Mn/ZnO interface with 4 ML of manganese deposited onto the ZnO surface was annealed up to 500ºC. No Mn capping layer was found at the surface after annealing as was confirmed by scanning Auger spectroscopy experiment. We used a resonant photoemission to extract the Mn3d partial density of states in photoemission spectra. The Mn3d states contribute to the electronic structure of the system within 10 eV of the Fermi level. They show three features: a main peak at 3.8-4.5 eV, a valence structure at the top of the valence band (1-3 eV), and a broad satellite situated between 5.5 and 9 eV below E_F. The satellite/main branching ratio was determined to be 0.43, which is a fingerprint of strong hybridization between the Mn3d electrons and the valence band of the crystal. The hybridization effect in Zn_{1-x} Mn_xO surface alloy is comparable to Zn_{1-x}Mn_xS and much higher than in Zn_{1-x}Mn_xSe, Zn_{1-x}Mn_xTe, and Ga_{1-x}Mn_xAs semimagnetic compounds.
7
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Resonant Photoemission Spectroscopy Study on the Contribution of the Yb 4f States to the Electronic Structure of ZnO

76%
Demchenko I., Melikhov Y., Konstantynov P., Ratajczak R., Barcz A., Guziewicz E.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
907-909
EN
The electronic structure of Yb implanted ZnO has been studied by the resonant photoemission spectroscopy. The contribution of the Yb 4f partial density of states is predominant at binding energy about 7.5 and ≈11.7 eV below the VB maximum. At photon energy about 182 eV the multiplet structure around 11.7 eV shows the strongest resonance that corresponds to the ¹I multiplet which is almost exclusively responsible for this resonance, while ³H and ³F states are responsible for the resonance around 7.5 eV. It was also found that the Yb 4f partial density of states distribution shows some similarity to Yb₂O₃.
8
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Characterization of n-ZnO/p-GaN Heterojunction for Optoelectronic Applications

76%
Wachnicki L., Gieraltowska S., Witkowski B., Figge S., Hommel D., Guziewicz E., Godlewski M.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
869-872
EN
An important feature of zinc oxide and gallium nitride materials are their similar physical properties. This allows to use them as a p-n junction materials for applications in optoelectronics. In earlier work we presented use of ZnO as a transparent contact to GaN, which may improve external efficiency of LED devices. In this work we discuss properties of a n-ZnO/p-GaN heterostructure and discuss its optimization. The heterostructure is investigated by us for possible applications, e.g. in a new generation of UV LEDs or UV light detectors.
9
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Cd_{1-x}Fe_{x}Te Ternary Crystal Formation Studied by Resonant Photoemission

76%
Guziewicz E., Kowalski B. J., Gołacki Z., Orłowski B. A., Johnson R. L., Masek J.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
793-796
EN
A resonant photoemission was used to study the ternary crystal formation, when small amount of Fe atoms was deposited (in one monolayer range of thickness) on the clean CdTe(100) surface. The constant initial state spectra taken near the Fe 3p-3d transition after Fe deposition and then again after heating process show the existence of two Fano-like resonance. The differences of the energy distribution curves taken for both resonance and antiresonance, respectively, allow us to distinguish two kind of Fe 3d contributions to the valence band: one derived from the metallic Fe islands on the surface and the second - derived from the Fe atoms built into the Cd_{1-x}Fe_{x}Te crystal.
10
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Optical and Structural Characterization of Zinc Oxide Nanostructures Obtained by Atomic Layer Deposition Method

76%
Wachnicki Ł., Witkowski B., Gierałtowska S., Kopalko K., Godlewski M., Guziewicz E.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 5
905-907
EN
Zinc oxide is a II-VI semiconductor material which is gaining increasing interest in various fields such as biology, medicine or electronics. This semiconductor reveals very special physical and chemical properties, which imply many applications including a transparent electrode in solar cells or LED diodes. Among many applications, ZnO is also a prospective material for sensor technology, where developed surface morphology is very advantageous. In this work we present ZnO nanowires growth using atomic layer deposition method. ZnO nanowires were obtained using controlled physical properties. As a substrate we used gallium arsenide with gold-gallium eutectic droplets prepared on the surface at high temperature. To obtain the eutectic solution there was put a gold thin film on GaAs through the sputtering and then we annealed the sample in a nitrogen gas flow. The so-prepared substrate was applied for growth of ZnO nanowires. We used deionized water and zinc chloride as oxygen and zinc precursors, respectively. The eutectic mixture serves as a catalyst for the ZnO nanowires growth. Au-Ga droplets flow on the front of ZnO nanowires. Scanning electron microscopy images show ZnO nanorods in a form of crystallites of up to 1 μm length and a 100 nm diameter. It is the first demonstration of the ZnO nanowires growth by atomic layer deposition using the vapour-liquid-solid approach.
11
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Cathodoluminescence Profiling for Checking Uniformity of ZnO and ZnCoO Thin Films

76%
Witkowski B., Łukasiewicz M., Wolska E., Kopalko K., Kowalski B., Guziewicz E., Godlewski M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
675-677
EN
We employ scanning electron microscopy and cathodoluminescence for evaluation of uniformity of ZnCoO films obtained by the atomic layer deposition. Cathodoluminescence quenching by Co ions allows us to detect (regions of weaker light emission) Co accumulations, with the resolution limited by diffusion length of secondary carriers.
12
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Resonant Photoemission Study of Gd 4f States in IV-VI Crystals

76%
Kowalski B. J., Gołacki Z., Guziewicz E., Orłowski B. A., Ghijsen J., Johnson R. L.
Acta Physica Polonica A
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1997
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vol. 91
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issue 4
819-823
EN
Resonant photoemission experiments were performed in order to reveal the contributions of half-filled Gd 4f^{7} shell to the electronic structures of Sn_{0.95}Gd_{0.05}Te and Pb_{0.95}Gd_{0.05}S crystals. The influences of the Gd 4f^{6} final-state multiplet splitting and f-ligand hybridization on the shapes of the spectra are discussed.
13
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4f Contribution to Valence Band of Pb_{1-x}RE_{x}S (RE = Eu,Gd) Studied by Resonant Photoemission

76%
Kowalski B., Gołacki Z., Guziewicz E., Orłowski B., Ghijsen J., Johnson R.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1035-1039
EN
Resonant photoemission experiments were carried out in order to reveal the contributions of partly filled Eu 4f^{7} and Gd 4f^{7} shells to the valence bands of Pb_{0.95}Eu_{0.05}S and Pb_{0.95}Gd_{0.05}S crystals. The coupling between these orbitals and the host electronic states is discussed.
14
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Cr 3d Surface and Bulk States in Sn_{1-x}Cr_{x}Te/Cr Crystals

76%
Guziewicz E., Szamota-Sadowska K., Kowalski B. J., Grodzicka E., Story T., Orłowski B. A., Johnson R. L.
Acta Physica Polonica A
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1997
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vol. 91
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issue 4
783-787
EN
We report a new approach to investigate metal-semiconductor interface formation. Photoemission spectroscopy was applied in order to investigate the clean surface of a Sn_{0.97}Cr_{0.03} Te crystal and to observe its changes under sequential deposition of small amounts of Cr atoms. In order to analyse the Cr 3d contribution to the valence band, the Fano-type resonance tuned to the Cr 3p-3d transition was used. The experiment was designed to follow the Sn_{0.97}Cr_{0.03} Te/Cr interface formation process. At the clean Sn_{0.97}Cr_{0.03}Te surface, the Cr 3d states contribution to the valence band was found to be positioned 0.8 eV below the Fermi level. After the Cr deposition processes the contribution shifted to a higher binding energy and another contribution 5.8 eV below the Fermi level was also observed.
15
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Electronic Band Structure of Cubic HgS

76%
Guziewicz E., Kowalski B., Orłowski B., Dybko K., Witkowska B., Szuszkiewicz W.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 2
395-398
EN
Reflectivity spectra of Hg_{1-x}Fe_{x}S (x < 0.04) and HgSe_{1-y}S_{y} (y < 0.5) mixed crystals were measured in the vacuum ultraviolet energy range from 4 to 12 eV. Information about the electronic band structure of cubic modi­fication of HgS resulting from the above data is analyzed and discussed.
16
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Visible Luminescence from Porous Silicon

76%
Bała W., Firszt F., Nossarzewska-Orłowska E., Brzozowski A., Orłowski B., Kowalski B., Guziewicz E.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
761-764
EN
This paper presents results of investigation of the temperature dependence of visible luminescence in porous silicon layers prepared by anodization in hydrofluoric acid. Luminescence spectra were measured in the temperature range between 40 K and 350 K. Room temperature reflectivity spectra were also measured in vacuum ultraviolet radiation range from 4 eV to 12 eV.
17
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X-ray Absorption Fine Structure Investigation of the Low Temperature Grown ZnCoO Films

76%
Wolska A., Klepka M., Witkowski B., Witkowski M., Guziewicz E., Godlewski M.
Acta Physica Polonica A
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2012
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vol. 121
|
issue 4
883-887
EN
ZnO based diluted magnetic semiconductors are intensively investigated for possible spintronic applications. In the present work we investigate the ZnCoO layers grown at low temperature by atomic layer deposition. The local atomic structure of a series of layers with different Co concentration is investigated by the X-ray absorption fine structure measurements. Two groups of ZnCoO layers are investigated - the ones with an uniform Co distribution and highly nonuniform films. For uniform samples we observe that a majority of Co atoms is built into the ZnO matrix substituting the Zn atoms. In contrast, for the nonuniform samples, metallic Co inclusions are also observed. These results are in strong correlation with the magnetic properties of the films studied separately. Samples with the uniform Co distribution (Co substitutes Zn in ZnO) are paramagnetic, whereas the nonuniform ones show a ferromagnetic response.
18
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Synchrotron Photoemission Study of Ferromagnetic (Zn,Co)O Films

76%
Guziewicz E., Lukasiewicz M., Wachnicki L., Kopalko K., Dłużewski P., Jakiela R., Godlewski M.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-40-A-42
EN
The electronic structure of ferromagnetic (Zn,Co)O films was investigated by resonant photoemission across the Co 3p → Co 3d photoionization threshold, e.g. using photon energy between 50 eV and 66 eV. The films were grown by atomic layer deposition at temperature between 160C and 300C and they differed in distribution and content of cobalt. The maximum of the Fano resonance was observed at photon energy 63 eV, whereas the minimum at 58 eV. The difference between energy distribution curves taken at 63 eV and the one taken at 58 eV was calculated for a series of samples. It shows that the Co 3d contribution to the valence band electronic structure of ferromagnetic (Zn,Co)O films differs significantly from that of the films which show the paramagnetic response.
19
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Valence Band Density of States and Mn 3d Contribution in Mn_{1-x}Mg_{x}Te

76%
Kowalski B., Guziewicz E., Kopalko K., Orłowski B., Janik E., Wojtowicz T., Johnson R.
Acta Physica Polonica A
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1998
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vol. 94
|
issue 3
401-405
EN
Resonant photoemission spectroscopy was applied to determine the Mn 3d derived contribution to the valence band density of states of Mn_{0.44} Mg_{0.56}Te grown by molecular beam epitaxy on a GaAs(001) substrate. The modifications of the valence band density-of-states distribution are discussed as a consequence of the substitution of Mg ions for Mn ions.
20
Content available remote

Optical Properties of ZnCoO Films and Nanopowders

76%
Wolska E., Łukasiewicz M., Fidelus J., Łojkowski W., Guziewicz E., Godlewski M.
Acta Physica Polonica A
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2009
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vol. 116
|
issue 5
918-920
EN
ZnCoO is one of the most studied and promising semiconductor materials for spintronics applications. In this work we discuss optical and electrical properties of ZnCoO films and nanoparticles grown at low temperature by either atomic layer deposition or by a microwave driven hydrothermal method. We report that doping with cobalt quenches a visible photoluminescence of ZnO. We could observe a visible photoluminescence of ZnO only for samples with very low Co fractions (up to 1%). Mechanisms of photoluminescence quenching in ZnCoO are discussed. We also found that ZnO films remained n-type conductive after doping with Co, indicating that a high electron concentration and cobalt 2+ charge state can coexist.
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