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1
Content available remote

Optical Characterization of ZnO Nanorods Grown by the Ultra-Fast and Low Temperature Hydrothermal Process

100%
Witkowski B., Ivanov V., Wachnicki Ł., Gierałtowska S., Godlewski M.
Acta Physica Polonica A
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2016
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vol. 130
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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.
2
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Electronic Properties of Stacked ZrO₂ Films Fabricated by Atomic Layer Deposition on 4H-SiC

100%
Król K., Kwietniewski N., Gierałtowska S., Wachnicki Ł., Sochacki M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
329-331
EN
The electronic properties of ZrO₂/SiO₂ stacked dielectric layers are reported as a function for temperature of the atomic layer deposition process. A dielectric layer has been characterized by C-V and I-V measurements of MIS structures. A strong dependence of κ value of ZrO₂ layer has been observed as a function of deposition temperature T. The values within the range of κ≈16-26 have been obtained. All measured stacked dielectric layers show an increase in dielectric breakdown voltage compared to simple SiO₂ dielectric by average factor of 1.7 and factor of 2 (21 MV/cm) for high-κ oxides deposited at low temperature (85°C).
3
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Optical and Structural Characterization of Zinc Oxide Nanostructures Obtained by Atomic Layer Deposition Method

86%
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.
4
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High Quality Gate Insulator/GaN Interface for Enhancement-Mode Field Effect Transistor

86%
Taube A., Kruszka R., Borysiewicz M., Gierałtowska S., Kamińska E., Piotrowska A.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-22-A-24
EN
The capacitance-voltage measurements were applied for characterization of the semiconductor/dielectric interface of GaN MOS capacitors with SiO_2 and HfO_2/SiO_2 gate stacks. From the Terman method low density of interface traps (D_{it} ≈ 10^{11} eV^{-1} cm^{-2}) at SiO_2/GaN interface was calculated for as-deposited samples. Samples with HfO_2/SiO_2 gate stacks have higher density of interface traps as well as higher density of mobile charge and effective charge in the dielectric layers. High quality of SiO_2/GaN interface shows applicability of SiO_2 as a gate dielectric in GaN MOSFET transistors.
5
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Barriers in Miniaturization of Electronic Devices and the Ways to Overcome Them - from a Planar to 3D Device Architecture

86%
Godlewski M., Guziewicz E., Gierałtowska S., Łuka G., Krajewski T., Wachnicki Ł., Kopalko K.
Acta Physica Polonica A
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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.
6
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Properties and Characterization of ALD Grown Dielectric Oxides for MIS Structures

73%
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.
7
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Structure Dependent Conductivity of Ultrathin ZnO Films

73%
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.
8
Content available remote

Electronic Properties of Thin HfO_2 Films Fabricated by Atomic Layer Deposition on 4H-SiC

73%
Taube A., Gierałtowska S., Gutt T., Małachowski T., Pasternak I., Wojciechowski T., Rzodkiewicz W., Sawicki M., Piotrowska A.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
696-698
EN
Applicability of thin HfO_2 films as gate dielectric for SiC MOSFET transistor is reported. Layers characterisation was done by means of atomic force microscopy and scanning electron microscopy, spectroscopic ellipsometry and C-V and I-V measurements of MIS structures. High permittivity dielectric layers were deposited using atomic layer deposition. Investigation showed high value of κ = 15 and existence of high density surface states (5 × 10^{12} eV^{-1} cm^{-2}) on HfO_2/SiC interface. High leakage current is caused probably due to low conduction band offset between hafnium oxide and silicon carbide.
9
Content available remote

Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

73%
Czapkiewicz M., Cywiński G., Dybko K., Siekacz M., Wolny P., Gierałtowska S., Guziewicz E., Skierbiszewski C., Wróbel J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1026-1028
EN
We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are defined by the integration of side and top gates in a single device. In this configuration, the planar gates are located on the both sides of a quantum channel and the metallic top gates, which cover the active region, are separated from the substrate by an insulating and passivating layers of HfO_2 or Al_2O_3/HfO_2 composite. The properties of devices have been tested at T = 4.2 K. For side gates we have obtained a very small surface leakage current I_g< 10^{-11} A at gate voltages |V_g| < 2 V, however, it is not enough to close the quantum channel. With top gates we have been able to reach the pinch-off voltage at V_g = - 3.5 V at a cost of I_g ≈ 10^{-6} A, which has been identified as a bulk leakage current.
10
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Content available

Si/ZnO nanorods with Ag nanoparticles/AZO heterostructures in PV applications

73%
Gwóźdź K., Płaczek-Popko E., Gumienny Z., Zielony E., Pietruszka R., Witkowski B. S., Wachnicki Ł., Gierałtowska S., Godlewski M., Chang L. B.
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2016
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issue 3
11
Content available remote

RBS/Channeling Analysis of Zinc Oxide Films Grown at Low Temperature by Atomic Layer Deposition

73%
Ratajczak R., Stonert A., Guziewicz E., Gierałtowska S., Krajewski T., Luka G., Wachnicki L., Witkowski B., Godlewski M.
Acta Physica Polonica A
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2013
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vol. 123
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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.
12
Content available remote

(Zn,Cu)O Films by Atomic Layer Deposition - Structural, Optical and Electric Properties

73%
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
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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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