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1
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Thermal Donor Generation in Boron- and Aluminium-Doped Czochralski Silicon

100%
Kopalko K., Kaczor P., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1991
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vol. 80
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issue 3
345-348
EN
Generation of thermal donor centres in oxygen-rich silicon doped with boron and aluminium acceptors has been studied with the FTIR technique. It has been found that upon annealing 470°C two kinds of absorption series were generated. One of them belonged to the well-known first ionization level of silicon thermal (double) donors (TD's): TD°/TD^{+} . The second series was identified with the so-called shallow thermal donors (STD's). The generation kinetics of the two series was followed for both kinds of acceptor doping and significant differences has been found. The results of the FTIR investigations were further compared with the magnetic resonance findings allowing for their mutual correlation and more general conclusions.
2
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Infrared Absorption Study of Thermally Generated Shallow Donor Centers in Czochralski Silicon

100%
Kaczor P., Kopalko K., Godlewski M., Gregorkiewicz T.
Acta Physica Polonica A
|
1992
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vol. 82
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issue 4
677-680
EN
A comparative study of thermally generated donor centers in boron and aluminum doped Czochralski silicon was performed by means of Fourier transform infrared technique. A detailed study revealed presence of donor centers belonging to the well-known series of thermal donors and shallow thermal donors. For both types of material the same centers could be observed while considerable differences in their generation kinetics occurred. In addition to the previously identified species also new ones could be observed. One of them, with single ionization level at approximately 39.5 meV, was found to exhibit clear dependence of its concentration upon illumination of the sample during cooling from room temperature to liquid He temperature.
3
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Quasi Fermi Levels in Semiconductor Photovoltaic Heterojunction

100%
Orlowski B., Pieniazek A., Goscinski K., Kopalko K.
|
EN
The photovoltaic heterojunction elements are build of two different semiconductors of n and p type. Under cell illumination the same density of n and p carriers are created in each generation point but it leads to the remarkably higher increase of relative concentration for minority than for majority carriers. It is causing bigger energy change of the quasi Fermi level of minority than of majority carriers. The minority carriers decide of the value of generated photovoltage while the majority carriers contribution to it, in most cases can be neglected. Measured change of the generated open circuit photovoltage versus illumination light intensity allows to estimate corresponding to it increase of the minority carrier concentration. These allows as well to scan the part of the forbidden gap region by the minority carriers quasi Fermi level and in a case of impurity or defect levels located in forbidden gap it can influence on the continuous dependence of generated photovoltage versus light intensity e.g. for pinning of the Fermi level. To create efficient photovoltaic heterojunction it will need to study electronic properties of the used impurities and their proper distribution in the region of junction.
4
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Epitaxial Growths of II-VI Compounds on (110) Substrates

88%
Cywiński G., Wojtowicz T., Kopalko K., Karczewski G., Kossut J.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
281-284
EN
We studied epitaxial growth conditions of II-VI semiconductors on (110) substrates, which is indispensable for fabrication of T-shaped quantum wire structures. We experimented with different types of (110)-oriented substrates and monitored the surface quality of deposited layers in situ by reflection high energy electron diffraction and ex situ by photoluminescence. The aim of this work is to find optimum growth conditions of II-VI compounds on a cleaved edge of a superlattice as required by the overgrowth method.
5
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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.
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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Band Structure of Mn/ZnTe Studied, by Angle-Resolved Photoelectron Spectroscopy

76%
Kowalski B., Orlowski B., Pietrzyk M., Kaczor P., Kopalko K., Mickievicius S., Johnson R.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
735-740
EN
The electronic band structure of Mn/ZnTe(110) (1×1) has been studied by angle-resolved photoelectron spectroscopy. The sets of spectra were acquired for the clean surface and after in situ deposition of 0.4 ML of Mn, in order to compare the band structures and to reveal changes brought about by the presence of Mn. The experimental band structure diagram of Mn/ZnTe along theΓ-K direction in the Brillouin zone has been derived from the experimental data. Indications of interaction between the Mn 3d states and sp^3 bands of the semiconductor are discussed.
8
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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
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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.
9
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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.
10
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Comparison of Optical Properties of CdTe/CdMnTe Quantum Wells Grown by Molecular Beam and Atomic Layer Epitaxy

76%
Godlewski M., Kopalko K., Wojtowicz T., Karczewski G., Kossut J., Bergman J., Monemar B.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1012-1016
EN
Optical properties of a series of CdTe/CdMnTe multi quantum well structures grown with MBE and ALE (CdTe quantum wells only) methods are compared. Based on the results of the photoluminescence experiments we conclude that the ALE growth leads to a different lateral scale of quantum well width fluctuations, which results in different exciton properties in two multi quantum well systems studied. In the wells grown with ALE method excitons are less localized. They can migrate in a quantum well plane between quantum well regions varying in thickness by 1 monolayer.
11
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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.
12
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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
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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.
13
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Substrates Grown from the Vapor for ZnO Homoepitaxy

76%
Skupiński P., Kopalko K., Łusakowska E., Domukhovski V., Jakieła R., Mycielski A., Grasza K.
Acta Physica Polonica A
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2008
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vol. 114
|
issue 5
1361-1368
EN
The novel method of preparation of epi-ready ZnO substrates is demonstrated. The substrates were made of unique ZnO crystals grown by chemical vapor transport method using hydrogen as the transport agent. The effect of low-level doping (Mn, Co, Cu, and V) on the structural quality of the crystals was investigated. Atomic layer deposition was used to verify usability of the substrates for homoepitaxy. The thermal annealing prior to the atomic layer deposition process and effect of thermal annealing of the epitaxial layers was studied. The X-ray diffraction and atomic force microscopy methods were applied to study the structural quality of the ZnO layers. Detection of the dopants in the substrates by secondary ion mass spectroscopy made possible the measurement of the thickness of the layers. The obtained root mean square roughness for both the substrates and layers ranged between 0.2 nm and 5 nm, and was dependent on the sample crystallographic orientation and sequence of polishing and annealing procedures. The optimal recipe for the epi-ready substrate preparation was formulated.
14
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Barriers in Miniaturization of Electronic Devices and the Ways to Overcome Them - from a Planar to 3D Device Architecture

76%
Godlewski M., Guziewicz E., Gierałtowska S., Łuka G., Krajewski T., Wachnicki Ł., Kopalko K.
Acta Physica Polonica A
|
2009
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vol. 116
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issue S
S-19-S-21
EN
We witness a new revolution in electronic industry - a new generation of integrated circuits uses as a gate isolator HfO_{2}. This high-k oxide was deposited by the atomic layer deposition technique. The atomic layer deposition, due to a high conformality of deposited films and low growth temperature, has a large potential to be widely used not only for the deposition of high-k oxides, but also of materials used in solar cells and semiconductor/organic material hybrid structures. This opens possibilities of construction of novel memory devices with 3D architecture, photovoltaic panels of the third generation and stable in time organic light emitting diodes as discussed in this work.
15
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Monocrystalline and Polycrystalline ZnO and ZnMnO Films Grown by Atomic Layer Epitaxy - Growth and Characterization

64%
Wójcik A., Kopalko K., Godlewski M., Łusakowska E., Paszkowicz W., Dybko K., Domagała J., Szczerbakow A., Kamińska E.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
667-673
EN
Recently we demonstrated growth of monocrystalline ZnO films by atomic layer epitaxy in the gas flow variant using inorganic precursors. In this study, we discuss properties of ZnO films grown with organic precursors. Successful Mn doping of the ZnO films during the growth was achieved using the Mn-thd complex. Secondary ion mass spectroscopy and X-ray investigations reveal the contents of Mn up to about 20% of the cationic component.
16
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Temperature Study of Photoluminescence from Deep CdTe/Cd_{1-x}Mn_{x}Te Quantum Wells

64%
Kutrowski M., Wojtowicz T., Karczewski G., Kopalko K., Zakrzewski A. K., Janik E., Grasza K., Łusakowska E., Kossut J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
500-504
EN
The photoluminescence studies in CdTe/CdMnTe quantum wells are reported in the temperature range 10-300 K. The MnTe concentration in the barriers is x = 0.3, 0.5, 0.63 and 0.68. Thus the potential wells in our samples are very deep, of the order of ≈ 800 meV in the conduction band and ≈ 200 meV in the valence band in the case of the x = 0.68 sample. In spite of the large lattice mismatch (related to high x value) between the wells and the barriers the observed line widths are as narrow as 2 meV in the case of 100 Å. Clear manifestations of internal strain are observed. In particular, the temperature coefficient of the luminescence energies shows strong dependence on the width of wells.
17
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Digital Magnetic Quantum Wells for the Study of Interface Sharpness of Molecular Beam Epitaxy Grown Structures

64%
Wojtowicz T., Karczewski G., Żakrzewski A., Kutrowski M., Janik E., Dynowska E., Kopalko K., Kret S., Kossut J., Laval J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
165-168
EN
We report on the growth and basic characterization of digital magnetic quantum wells, that is, quantum wells in which the well material is itself a short period superlattice composed of alternating diluted magnetic and nonmagnetic semiconductor layers each only a few monolayers thick. These novel structures can be useful in a variety of studies, including studies of barrier-well interface sharpness.
18
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Hybrid Organic/ZnO p-n Junctions, with n-Type ZnO, Grown by Atomic Layer Deposition

64%
Łuka G., Krajewski T., Szczerbakow A., Łusakowska E., Kopalko K., Guziewicz E., Wachnicki Ł., Szczepanik A., Godlewski M., Fidelus J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1229-1234
EN
We report on fabrication of hybrid inorganic-on-organic thin film structures with polycrystalline zinc oxide films grown by atomic layer deposition technique. ZnO films were deposited on two kinds of thin organic films, i.e. pentacene and poly(dimethylosiloxane) elastomer with a carbon nanotube content (PDMS:CNT). Surface morphology as well as electrical measurements of the films and devices were analyzed. The current density versus voltage (I-V) characteristics of ITO/pentacene/ZnO/Au structure show a low-voltage switching phenomenon typical of organic memory elements. The I-V studies of ITO/PDMS:CNT/ZnO/Au structure indicate some charging effects in the system under applied voltages.
19
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Structure Dependent Conductivity of Ultrathin ZnO Films

64%
Snigurenko D., Kopalko K., Krajewski T., Łuka G., Gierałtowska S., Witkowski B., Godlewski M., Dybko K., Paszkowicz W., Guziewicz E.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1042-1044
EN
Zinc oxide films dedicated for hybrid organic/inorganic devices have been studied. The films were grown at low temperature (100°C, 130C and 200°C) required for deposition on thermally unstable organic substrates. ZnO layers were obtained in atomic layer deposition processes with very short purging times in order to shift a structure of the films from polycrystalline towards amorphous one. The correlation between atomic layer deposition growth parameters, a structural quality and electrical properties of ZnO films was determined.
20
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(Zn,Cu)O Films by Atomic Layer Deposition - Structural, Optical and Electric Properties

64%
Łukasiewicz M., Witkowski B., Wachnicki Ł., Kopalko K., Gierałtowska S., Wittlin A., Jaworski M., Guziewicz E., Godlewski M.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-34-A-36
EN
ZnCuO thin films have been deposited on silicon, glass and quartz substrates by atomic layer deposition method, using reactive organic precursors of zinc and copper. As zinc and copper precursors we applied diethylzinc and copper(II) acetyloacetonate. Structural, electrical and optical properties of the obtained ZnCuO layers are discussed based on the results of scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, atomic force microscopy, the Hall effect and photoluminescence investigations.
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