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1
Content available remote

Influence of Annealing on Optical Properties of ZnO Nanorods Obtained by the Microwave-Assisted Hydrothermal Process

100%
Materska P., Witkowski B., Godlewski M.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 5
1202-1204
EN
Optical properties of ZnO nanorods (of different sizes, grown on two different substrates) are investigated. Nanorods were grown using microwave-assisted hydrothermal process on gallium nitride or silicon substrate. To initiate nanorods growth on a silicon substrate ZnO nucleation layer was used. ZnO nanoseeds were deposited by atomic layer deposition. For GaN substrate an epitaxial relation was observed. For both substrates nanorods show a hexagonal structure, expected for wurtzite ZnO. Results of nanorods annealing are discussed.
2
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ZnO Nanopowders by a Microwave Hydrothermal Method - Influence of the Precursor Type on Grain Sizes

100%
Wolska E., Witkowski B., Godlewski M.
Acta Physica Polonica A
|
2011
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vol. 119
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issue 5
683-685
EN
Two series of ZnO nanopowders obtained by a microwave hydrothermal method are examined. We used two different zinc precursors (zinc chloride (ZnCl_2) and zinc nitrate hexahydrate (N_2O_6Zn·6H_2O)). Both types of nanopowders show a bright emission in a visible light, including the band edge emission, which indicates their good crystallographic quality. Results of scanning electron microscopy, photo- and cathodoluminescence investigations are presented.
3
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The Effect of Synthesis Pressure on Properties of Eu-Doped ZnO Nanopowders Prepared by Microwave Hydrothermal Method

88%
Rosowska J., Kaszewski J., Witkowski B., Wachnicki Ł., Godlewski M.
Acta Physica Polonica A
|
2016
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vol. 130
|
issue 5
1205-1208
EN
In the current research, europium doped ZnO nanopowders prepared by a microwave hydrothermal method are investigated. The effects of synthesis pressure on the morphologies, crystal structures, and optical properties of Eu-doped ZnO were analyzed by scanning electron microscopy, X-ray diffraction, cathodo- and photoluminescence. From our investigations it can be concluded that the synthesis pressure strongly influences the surface morphology. With the increase of the synthesis pressure from 2 MPa to 10 MPa significant changes can be observed. An increase of the mean crystallites sizes and change of the intensity ratio between the near band edge and defect related deep level emission band of ZnO were observed.
4
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Optical Characterization of ZnO Nanorods Grown by the Ultra-Fast and Low Temperature Hydrothermal Process

88%
Witkowski B., Ivanov V., Wachnicki Ł., Gierałtowska S., Godlewski M.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 5
1199-1201
EN
The results of photoluminescence investigations of zinc oxide nanorods are reported. These nanorods grown on undoped silicon substrates were obtained by low temperature and ultra-fast version of a microwave-assisted hydrothermal method. The photoluminescence investigations show very high quality of the obtained material. From photoluminescence studies we conclude the lack of carrier localization effects. The photoluminescence is dominated by band gap edge emission of bound excitonic (donor bound excitons) origin. Thus, the photoluminescence quenching observed at increased temperatures is associated with thermal ionization of shallow donors. From photoluminescence analysis (changes of photoluminescence line width) a strength of exciton-acoustic phonon coupling is evaluated.
5
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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
|
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.
6
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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.
7
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Photoluminescence and Chromaticity Properties of ZnO Nanopowders Made by a Microwave Hydrothermal Method

76%
Wolska E., Sibera D., Witkowski B., Yatsunenko S., Pełech I., Narkiewicz U., Godlewski M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
908-910
EN
Four series of ZnO nanopowders obtained by a microwave hydrothermal method are examined. Two different solvents (ethanol and distilled water) and different values of pressure during heating in the reactor were used. The obtained nanopowders show a bright emission covering visible light spectral region, including the band edge emission. Results of scanning electron microscopy, X-ray diffraction, photo- and cathodoluminescence investigations and also CIE1961 chromaticity diagram are presented.
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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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
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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.
11
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Properties and Characterization of ALD Grown Dielectric Oxides for MIS Structures

64%
Gierałtowska S., Sztenkiel D., Guziewicz E., Godlewski M., Łuka G., Witkowski B., Wachnicki Ł., Łusakowska E., Dietl T., Sawicki M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
692-695
EN
We report on an extensive structural and electrical characterization of undergate dielectric oxide insulators Al_2O_3 and HfO_2 grown by atomic layer deposition. We elaborate the atomic layer deposition growth window for these oxides, finding that the 40-100 nm thick layers of both oxides exhibit fine surface flatness and required amorphous structure. These layers constitute a base for further metallic gate evaporation to complete the metal-insulator-semiconductor structure. Our best devices survive energizing up to ≈ 3 MV/cm at 77 K with the leakage current staying below the state-of-the-art level of 1 nA. At these conditions the displaced charge corresponds to a change of the sheet carrier density of 3 × 10^{13} cm^{-2}, which promises an effective modulation of the micromagnetic properties in diluted ferromagnetic semiconductors.
12
Content available remote

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
|
2012
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vol. 122
|
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.
13
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RBS/Channeling Analysis of Zinc Oxide Films Grown at Low Temperature by Atomic Layer Deposition

64%
Ratajczak R., Stonert A., Guziewicz E., Gierałtowska S., Krajewski T., Luka G., Wachnicki L., Witkowski B., Godlewski M.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 5
899-903
EN
The results of the Rutherford backscattering/channeling study of ZnO layers are presented. ZnO layers were deposited on the silicon single crystals and GaN epitaxial layers at low temperature by atomic layer deposition. Deposition temperature varied between 100 and 300°C. A random spectra analysis was performed to determine layer thickness and composition. In turn, analysis of the aligned spectra allows us to study evolution of ingrown defects. The Rutherford backscattering study supports the results of X-ray photoelectron spectroscopy measurements, performed separately, that the ZnO-ALD layers deposited at low temperature contain a higher oxygen content. Composition measurements, performed as a function of growth temperature, show that oxygen content decreases with the increasing temperature of the atomic layer deposition growth process.
14
Content available remote

Properties of GaN Nanocolumns Grown by Plasma - Assisted MBE on Si (111) Substrates

64%
Zytkiewicz Z., Dluzewski P., Borysiuk J., Sobanska M., Klosek K., Witkowski B., Setkiewicz M., Pustelny T.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-15-A-16
EN
We report on growth of GaN nanocolumns by plasma assisted MBE on (111) silicon substrates and on their characterization. The nanocolumns nucleate on the substrate spontaneously without use of any catalyst, probably by the Volmer-Weber mechanism. Transmission electron microscopy analysis shows high crystalline quality of GaN nanocolumns and their good alignment with the c-axis being perpendicular to the substrate. Preliminary results on use of GaN nanocolumns in gas sensor devices are presented.
15
Content available remote

(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
|
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.
16
Content available remote

ZnO by ALD - Advantages of the Material Grown at Low Temperature

64%
Guziewicz E., Godlewski M., Krajewski T., Wachnicki Ł., Łuka G., Paszkowicz W., Domagała J., Przeździecka E., Łusakowska E., Witkowski B.
Acta Physica Polonica A
|
2009
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vol. 116
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issue 5
814-817
EN
The 3D-architecture is a prospective way in miniaturization of electronic devices. However, this approach can be realized only if metal paths are placed not only at the top, but also beneath the electronic parts, which imposes drastic temperature limitations for the electronic device processing. Therefore last years a lot of investigations are focused on materials which can be grown at low temperature with electrical parameters appropriate for electronic applications. Zinc oxide grown by the atomic layer deposition method is one of the materials of choice. We obtained ZnO-ALD films at growth temperature range between 100°C and 200°C, and with controllable electrical parameters. Free carrier concentration was found to scale with deposition temperature, so it is possible to grow ZnO films with desired conductivity without any intentional doping. We used correlation of electrical and optical parameters to optimize the deposition process. Zinc oxide layers obtained in that way have free carrier concentration as low as 10^{16} cm^{-3} and high mobility (10-50 cm^{2}/(Vs)), which satisfies requirements for a material used in three-dimensional memories.
17
Content available remote

Epitaxial ZnO Films Grown at Low Temperature for Novel Electronic Application

52%
Wachnicki Ł., Dużyńska A., Domagala J., Witkowski B., Krajewski T., Przeździecka E., Guziewicz M., Wierzbicka A., Kopalko K., Figge S., Hommel D., Godlewski M., Guziewicz E.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 6A
A-7-A-10
EN
Monocrystalline films of zinc oxide were grown at 300C by atomic layer deposition. ZnO layers were grown on various substrates like ZnO bulk crystal, GaN, SiC and Al_2O_3. Electrical properties of the films depend on structural quality. Structural quality, surface morphology and optical properties of ZnO films were characterized using X-ray diffraction, scanning electron microscopy, and photoluminescence, respectively. High resolution X-ray diffraction spectra show that the rocking curve FWHM of the symmetrical 00.2 reflection equals to 0.058° and 0.009° for ZnO deposited on a gallium nitride template and a zinc oxide substrate, respectively. In low temperature photoluminescence sharp excitonic lines in the band-edge region with a FWHM equal to 4 meV, 5 meV and 6 meV, for zinc oxide deposited on gallium nitride, zinc oxide and sapphire substrate, respectively.
18
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Schottky Junctions Based on the ALD-ZnO Thin Films for Electronic Applications

52%
Krajewski T., Luka G., Smertenko P., Zakrzewski A., Dybko K., Jakiela R., Wachnicki L., Gieraltowska S., Witkowski B., Godlewski M., Guziewicz E.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-17-A-21
EN
The ZnO-based Schottky diodes revealing a high rectification ratio may be used in many electronic devices. This paper demonstrates several approaches to obtain a ZnO-based Schottky junction with a high rectification ratio. The authors tested several methods such as: post-growth annealing of the ZnO layer, acceptor (nitrogen) doping, as well as the ZnO surface coating with a properly chosen dielectric material. The influence of these approaches on the diode's rectification ratio together with modeling based on the differential approach and thermionic emission theory are presented.
19
Content available remote

ZnCoO Films by Atomic Layer Deposition - Influence of a Growth Temperature οn Uniformity of Cobalt Distribution

52%
Łukasiewicz M., Witkowski B., Godlewski M., Guziewicz E., Sawicki M., Paszkowicz W., Łusakowska E., Jakieła R., Krajewski T., Kowalik I., Kowalski B.
Acta Physica Polonica A
|
2009
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vol. 116
|
issue 5
921-923
EN
We report on the structural, electrical and magnetic properties of ZnCoO thin films grown by atomic layer deposition method using reactive organic precursors of zinc and cobalt. As a zinc precursor we applied either dimethylzinc or diethylzinc and cobalt(II) acetyloacetonate as a cobalt precursor. The use of these precursors allowed us the significant reduction of a growth temperature to 300°C and below, which proved to be very important for the growth of uniform films of ZnCoO. Structural, electrical and magnetic properties of the obtained ZnCoO layers will be discussed based on the results of secondary ion mass spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, atomic force microscopy, Hall effect and SQUID investigations.
20
Content available remote

Capability of Semiconducting NiO Films in Gamma Radiation Dosimetry

52%
Guziewicz M., Jung W., Grochowski J., Borysiewicz M., Golaszewska K., Kruszka R., Baranska A., Piotrowska A., Witkowski B., Domagala J., Gryzinski M., Tyminska K., Stonert A.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-69-A-72
EN
Electrical properties of RF magnetron sputtered p-NiO films were characterized after fabrication and after gamma irradiations using ^{137}Cs and ^{60}Co sources. Electrical parameters are obtained from the Hall measurements, impedance spectroscopy and C-V measurement of n-Si/p-NiO junction diodes. The results show that resistivity of the NiO film is gradually increased following after sequential irradiation processes because of the decrease in holes' concentration. Hole concentration of a NiO film decreases from the original value of 4.36 × 10^{16} cm^{-3} to 2.86 × 10^{16} cm^{-3} after ^{137}Cs γ irradiation with doses of 10 Gy. In the case of γ irradiation from ^{60}Co source, hole concentration of the film decreases from 6.3 × 10^{16}/cm^3 to 4.1 × 10^{16}/cm^3 and to 2.9 × 10^{16}/cm^3 after successive expositions with a dose of 20 Gy.
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