Wyniki wyszukiwania - Biblioteka Nauki

1

Investigation of Porous Zn Growth Mechanism during Zn Reactive Sputter Deposition

100%

Borysiewicz M. , Wojciechowski T. , Dynowska E. , Kamińska E. , Piotrowska A.

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nr 5

1144-1148

EN

Ar-O-Zn plasma discharges created during DC reactive magnetron sputtering of a Zn target and RF reactive magnetron sputtering of a ceramic ZnO target were investigated and compared by means of the Langmuir probe measurements in order to determine the mechanism of growth of porous Zn films during DC-mode Zn reactive sputtering. The power supplied to the magnetrons during the sputtering was kept at 125 W and the plasma was characterised as a function of oxygen content in the sputtering gas mixture, ranging from 0 to 60% for two gas pressures related to porous Zn film deposition, namely 3 mTorr and 5 mTorr. Based on the correlation of plasma properties measurements with scanning electron microscope imaging and X-ray diffraction of the films deposited under selected conditions it was found that the growth of porous, polycrystalline Zn films was governed by high electron density in the plasma combined with a high electron temperature and an increased energy of the ions impinging on the substrate.

2

Low Temperature Processing of Nanostructures Based on II-VI Semiconductors Quantum Wells

86%

Majewicz M. , Śnieżek D. , Wojciechowski T. , Baran E. , Nowicki P. , Wojtowicz T. , Wróbel J.

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nr 5

1174-1176

EN

We report the first results of electron beam lithography processes performed on polymethyl methacrylate (PMMA) and hydrogen silsesquioxane (HSQ) resists, which have been pre-backed in vacuum at T ≤ 90°C. For such low temperature processing the lithographical resolution is reduced as compared to standard procedures, however, the exposure contrast and adhesion to CdTe and HgTe substrates have been sufficient for the fabrication of sub-μ m quantum devices. Furthermore, the new method of electrical microcontact forming is proposed, based on the local melting and annealing of an indium metal layer, performed with the application of accelerated electron beam. The method has been tested for CdTe/CdMgTe quantum wells using the lithography techniques, the exposure parameters have been optimized by inspecting the morphology of annealed metal film via the in situ imaging.

3

Magnetic Force Microscopy Study of Zn_{1-x}Co_{x}O Nanowires Grown by Rapid Thermal Evaporation

72%

Aleszkiewicz M. , Fronc K. , Aleszkiewicz P. , Zaleszczyk W. , Dziawa P. , Wojciechowski T. , Wojtowicz T. , Karczewski G.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

865-867

EN

In this work we studied domain structure of Zn_{1-x}Co_{x}O nanowires which are single arms of tetrapode crystals. The as-grown material exhibits hysteretic behavior even at room temperature as revealed by SQUID mesurements. In order to get insight into the magnetic properties of individual tetrapodes they were dismembered into nanowires of nanometric diameters, deposited on a flat substrate and imaged by magnetic force microscopy. A magnetic interaction between the magnetic force microscopy probe and single nanowires has been detected which confirms that nanometric volume of the material possesses a magnetic moment. The magnetic force microscopy contrast is attractively independent of the tip magnetization direction which indicates that shape anisotropy of nanowires is not strong enough to prevent occurrence of tip-induced magnetic field disturbance.

4

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

72%

Taube A. , Gierałtowska S. , Gutt T. , Małachowski T. , Pasternak I. , Wojciechowski T. , Rzodkiewicz W. , Sawicki M. , Piotrowska A.

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nr 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.

5

TEM Study of the Structural Properties of Nanowires Based on Cd, Zn, Te grown by MBE on Silicon Substrates

72%

Kaleta A. , Kret S. , Sanchez A. , Bilska M. , Kurowska B. , Szczepańska A. , Płachta J. , Wojnar P. , Wojciechowski T.

Acta Physica Polonica A

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2017

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tom 131

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nr 5

1399-1405

EN

In this work we report on the atomic structures, elemental distribution, defects and dislocations of three types of semiconductor nanowires: ZnTe, CdTe, and complex ZnTe/(Cd,Zn)Te core/shell hetero-nanowires grown by a molecular beam epitaxy on (111) Si substrate using a vapor-liquid-solid mechanism. The structural properties and the chemical gradients were measured by transmission electron microscopy methods. The nanowires reveal mainly sphalerite structure, however wurtzite nanowires were also observed.

6

Physical Properties of ZnCoO Tetrapods and Nanofibers

58%

Gas K. , Fronc K. , Dziawa P. , Knoff W. , Wojciechowski T. , Zaleszczyk W. , Baranowska-Korczyc A. , Morhange J. , Paszkowicz W. , Elbaum D. , Karczewski G. , Wojtowicz T. , Szuszkiewicz W.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

868-870

EN

In this paper the physical properties of two types of Co-doped ZnO nanostructures: tetrapods and nanofibers grown by a rapid thermal evaporation process and prepared by the electrospinning technique, respectively, were investigated and analyzed. Surface morphology of the samples was examined using scanning electron microscopy. X-ray diffraction measurements showed hexagonal wurtzite crystal structure of both types of investigated nanostructures. Both X-ray diffraction and Raman scattering data confirmed high phase purity of the samples. The magnetic properties studied with the use of the SQUID magnetometer confirmed a presence of ferromagnetic order in analyzed nanostructures. The observed photoluminescence spectra exhibited two groups of lines. The first one, in the ultraviolet spectral range, is due to the optical transitions close to ZnO band gap, the second one in the red region is most probably related to the Co^{2+} d-d internal transitions. The influence of native defects on the optical properties is also shown and discussed. All results reported here lead us to the conclusion that in the mixed crystal nanostructures obtained, a fraction of the Zn^{2+} ions is substituted by Co^{2+} ions.

7

Terahertz Response of a Point Contact Based on CdTe/CdMgTe Quantum Well in Magnetic Field

58%

Grigelionis I. , Białek M. , Grynberg M. , Czapkiewicz M. , Kolkovskiy V. , Wiater M. , Wojciechowski T. , Wróbel J. , Wojtowicz T. , But D. , Knap W. , Łusakowski J.

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nr 6

1069-1072

EN

A photoresponse at THz frequencies of a quantum point contact fabricated on a CdTe/CdMgTe quantum well was studied at low temperatures as a function of magnetic field. The spectra show a structure which was interpreted as resulting from the cyclotron resonance and magnetoplasmon excitations. The wavelength of the fundamental magnetoplasmon mode was found to be about 2 μm which coincides with one of dimensions of the point contact. We also discuss the possibility of coupling of magnetoplasmon modes to shallow impurity transitions in the quantum well.