Search results

1

Electron Transport in Submicron Wires of Semiconductors

100%

Wróbel J.

Acta Physica Polonica A

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1996

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vol. 90

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issue 4

691-701

EN

We review the methods of fabrication and transport properties of submicron II-VI, IV-VI and III-V semiconductor wires. Devices were prepared by electron-beam lithography and used for detailed magnetotransport studies, carried out at low (down to 30 mK) temperatures. We discuss a number of novel features obtained in ballistic, diffusive and localized transport regimes. In particular, we describe the universal conductance fluctuations for semimagnetic materials (CdMnTe) and discuss the edge channel transport for PbTe, PbSe and GaAs/GaAlAs systems.

2

Influence of the Selected Factors on Thermal Fatigue of the ADI in an Aspect of its Suitability as the Material for Metal Moulds

63%

Wróbel J., Zych J.

Archives of Metallurgy and Materials

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2014

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issue 2

3

Focusing with 2D Square Photonic Crystal with Concavo-Concavo Boundaries

52%

Palka N., Ciurapinski W., Wróbel J.

Acta Physica Polonica A

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2009

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vol. 116

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issue 3

368-370

EN

We studied focusing properties of 2D square photonic crystal with concavo-concavo boundaries. The photonic crystal is built by air holes in a uniform dielectric. The incident plane wave propagates through a section of the photonic crystal and efficient focusing is observed by finite difference time domain simulations. To analyze the properties of photonic crystal we calculated the photonic band structure and equal frequency contours for TE modes. In our simulation we consider influence of geometry of the concave structures on the focusing properties.

4

Artificial Neural Network to the Control of the Parameters of the Heat Treatment Process of Casting

52%

Bokota A., Kulawik A., Wróbel J.

Archives of Foundry Engineering

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2015

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issue 1

5

Linear and Non-Linear Response in T-Shaped Electron Waveguides

52%

Bek M., Bułka B., Wróbel J.

Acta Physica Polonica A

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2009

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vol. 116

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issue 5

829-831

EN

We present theoretical studies of three-terminal ballistic junction in linear and non-linear regime. Various conductance and voltage dips and peaks are observed and their origin is explained as influence of the bend resistance and the threshold effect.

6

Sequential separation of twin pregnancy electrocardiograms

52%

Wróbel J., Kotas M., Leski J. M.

Bulletin of the Polish Academy of Sciences: Technical Sciences

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2016

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issue 1

7

Optical Studies of HgCdMnTe Bicrystals

52%

Grabecki G., Wróbel J., Karczewski G.

Acta Physica Polonica A

|

1991

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vol. 79

|

issue 2-3

221-223

EN

We report preliminary results of optical measurements performed on Hg_{1-x-k}Cd_{x}Mn_{k}Te grain boundaries. Photovoltaic spectra and I-V characteristics under illumination exhibit metastable behavior, confirming our previous conclusions based on transport measurements under high hydrostatic pressure.

8

The Numerical Analysis of the Phenomena of Superficial Hardening of the Hot-Work Tool Steel Elements / Analiza Numeryczna Zjawisk Przypowierzchniowego Hartowania Elementów Ze Stali Narzędziowej Do Pracy Na Gorąco

52%

Bokota A., Kulawik A., Wróbel J., Szymczyk R.

Archives of Metallurgy and Materials

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2015

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issue 4

9

The Use of Numerical Modelling to Determine the Conditions of Regeneration of Medium Carbon Steel

51%

Kulawik A., Wróbel J., Bęczkowski R.

Archives of Metallurgy and Materials

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2017

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vol. 62

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issue 4

10

Observation of Two-Dimensional Electron Gas in LPE-Grown GaInAs-InP Heterostructures

46%

Fronc K., Grabecki G., Wróbel J., Dietl T., Gajewska M.

Acta Physica Polonica A

|

1991

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vol. 80

|

issue 3

449-452

EN

A series of GaInAs/InP heterostructures was grown by liquid phase epitaxy. The heterostructures were characterized by magnetotransport measurements carried out down to 1.8 K and up 10 T. The results demonstrate the existence of the high-mobility two-dimensional electron gas in the narrow-gap GaInAs as well as the presence of residual conductance through the InP buffer layer.

11

Bistability of (Ga,Mn)As Ferromagnetic Nanostructures Due to the Domain Walls Switching

39%

Andrearczyk T., Wosiński T., Mąkosa A., Figielski T., Wróbel J., Sadowski J.

Acta Physica Polonica A

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2009

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vol. 116

|

issue 5

901-903

EN

We designed and investigated four-arm nanostructures, composed of two perpendicularly crossed stripes, fabricated from ferromagnetic (Ga,Mn)As layer by means of electron-beam lithography patterning and chemical etching. The nanostructures exhibit a bistable resistance behavior resulting from two configurations of magnetic domain walls in the central part of the structures. We demonstrate a possibility of switching between two stable resistance states in zero magnetic field by applying a pulse of either weak magnetic field or electric current through the structure.

12

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

39%

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

Acta Physica Polonica A

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2014

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vol. 126

|

issue 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.

13

Mechanical and Electrical Properties, of ZnO-Nanowire/Si-Substrate Junctions Studied by Scanning Probe Microscopy

39%

Aleszkiewicz M., Fronc K., Wróbel J., Klepka M., Wojtowicz T., Karczewski G.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

255-260

EN

Scanning tunneling spectroscopy was used to check the tunneling I-V characteristics of junctions formed by n-ZnO nanowires deposited on Si substrates with n- and p-type electrical conductivity (i.e. n-ZnO nanowire/n-Si and n-ZnO nanowire/p-Si junctions, respectively). Simultaneously, several phenomena which influence the measured I-V spectra were studied by atomic force microscopy. These influencing factors are: the deposition density of the nanowires, the possibility of surface modification by tip movement (difference in attraction forces between nanowires and the p-Si and n-Si) and the aging of the surface.

14

Quantum Hall Ferromagnet in Magnetically-Doped Quantum Wells

33%

Andrearczyk T., Jaroszyński J., Wróbel J., Karczewski G., Wojtowicz T., Papis E., Kamińska E., Piotrowska A., Popović D., Dietl T.

Acta Physica Polonica A

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2003

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vol. 104

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issue 2

93-102

EN

The article reviews our recent studies on quantum Hall ferromagnetism in diluted magnetic semiconductors. We carried out magnetoresistance studies on modulation-doped, gated heterostructures of (Cd,Mn)Te/(Cd,Mg)Te:I. We put into evidence the formation of Ising quantum Hall ferromagnet with Curie temperature T_C as high as 2 K. Quantum Hall ferromagnetism is manifested by anomalous magnetoresistance maxima. Moreover, magnitude of these spikes depends dramatically on the history of the sample, shows hysteresis when either magnetic field or gate voltage are swept, stretched-exponential time evolution characteristic of glassy systems, and strong Barkhausen noise. Our study suggests that these metastabilities stem from the slow dynamics of ferromagnetic domains.

15

Magnetization Steps in Cd_{1-x}Mn_{x}Te Observed in Coherent Transport

33%

Jaroszyński J., Dietl T., Wróbel J., Karczewski G., Wojtowicz T., Kossut J., Maude D. K., van der Linden P., Portal J. C.

Acta Physica Polonica A

|

1997

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vol. 92

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issue 4

797-800

EN

Magnetoconductance measurements on submicron wires of n^{+}-Cd_{1-x}Mn_{x}Te were carried out up to 27 T and down to 100 mK. The inverse correlation field of the universal conductance fluctuations is found to increase abruptly in the vicinity of the magnetization steps due to Mn pairs in CdMnTe. No such effect is observed in similar wires of CdTe. These findings support a recent model, according to which the correlation field of the universal conductance fluctuations in magnetic systems is inversely proportional to the magnetic susceptibility of the localized spins.

16

Effects of Ballistic Transport in Wires of n-PbTe

33%

Grabecki G., Wróbel J., Dietl T., Papis E., Kamińska E., Piotrowska A., Ueta Y., Sprinholtz G., Bauer G.

Acta Physica Polonica A

|

1997

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vol. 92

|

issue 4

789-792

EN

We present results of magnetotransport studies on quantum wires of submicron PbTe epilayers, fabricated by means of electron beam lithography and dry etching. When the wire width is reduced down to 1 μm, the transition from diffusive to ballistic regime is observed. Effects associated with collimation and boundary scattering are found in the Hall, longitudinal, and van der Pauw magnetoresistance for wires and junctions in the shape of a cross.

17

Magneto-Transport Characterization of Four-Arm Nanostructure Based on Ferromagnetic (Ga,Mn)As

33%

Andrearczyk T., Wosiński T., Figielski T., Mąkosa A., Tkaczyk Z., Łusakowska E., Wróbel J., Sadowski J.

Acta Physica Polonica A

|

2008

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vol. 114

|

issue 5

1049-1054

EN

We report on results of magneto-transport measurements performed on four-arm nanostructure fabricated from p-type ferromagnetic Ga_{0.92}Mn_{0.08}As layer. The results reveal hysteresis-like behaviors of low field magnetoresistance. We interpret the magnetoresistance in terms of domain walls, which are expected to be trapped inside the nanostructure at some particular positions and which contribute to the total resistance.

18

Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

33%

Czapkiewicz M., Cywiński G., Dybko K., Siekacz M., Wolny P., Gierałtowska S., Guziewicz E., Skierbiszewski C., Wróbel J.

Acta Physica Polonica A

|

2012

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vol. 122

|

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.

19

Electron Localization in Sb-Doped Si/SiGe Superlattices

33%

Dietl T., Jaroszyński J., Sawicki M., Głód P., Wróbel J., Stöger G., Brunthaler G., Bauer G., Schäffler F.

Acta Physica Polonica A

|

1995

|

vol. 88

|

issue 4

699-702

EN

Millikelvin studies of in-plane magnetoconductance in short period Si/Ge:Sb superlattices have been carried out in order to examine the effect of anisotropy on quantum localization. The field-induced metal-to-insulator transition has been observed, indicating the existence of extended states. This suggests that despite anisotropy as large as D_{∥}/D_{⊥} ≈ 10^{3} the system behaves as 3D in respect of localization by disorder.

20

Magnetotransport through Nanoconstriction in Ferromagnetic Semiconductor (Ga,Mn)As

33%

Figielski T., Wosiński T., Pelya O., Sadowski J., Morawski A., Mąkosa A., Dobrowolski W., Jagielski J., Wróbel J.

Acta Physica Polonica A

|

2003

|

vol. 103

|

issue 6

525-531

EN

We studied narrow (submicron) constrictions in the layers of ferromagnetic semiconductor (Ga,Mn)As. We have demonstrated a contribution of the quantum localization effects to the magnetoresistance of the constricted samples. We have also found a negative contribution of a domain wall trapped in the constriction to the resistance, due presumably to the erasing of the localization effects by the domain wall.

Refine search results

Electron Transport in Submicron Wires of Semiconductors

Influence of the Selected Factors on Thermal Fatigue of the ADI in an Aspect of its Suitability as the Material for Metal Moulds

Focusing with 2D Square Photonic Crystal with Concavo-Concavo Boundaries

Artificial Neural Network to the Control of the Parameters of the Heat Treatment Process of Casting

Linear and Non-Linear Response in T-Shaped Electron Waveguides

Sequential separation of twin pregnancy electrocardiograms

Optical Studies of HgCdMnTe Bicrystals

The Numerical Analysis of the Phenomena of Superficial Hardening of the Hot-Work Tool Steel Elements / Analiza Numeryczna Zjawisk Przypowierzchniowego Hartowania Elementów Ze Stali Narzędziowej Do Pracy Na Gorąco

The Use of Numerical Modelling to Determine the Conditions of Regeneration of Medium Carbon Steel

Observation of Two-Dimensional Electron Gas in LPE-Grown GaInAs-InP Heterostructures

Bistability of (Ga,Mn)As Ferromagnetic Nanostructures Due to the Domain Walls Switching

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

Mechanical and Electrical Properties, of ZnO-Nanowire/Si-Substrate Junctions Studied by Scanning Probe Microscopy

Quantum Hall Ferromagnet in Magnetically-Doped Quantum Wells

Magnetization Steps in Cd_{1-x}Mn_{x}Te Observed in Coherent Transport

Effects of Ballistic Transport in Wires of n-PbTe

Magneto-Transport Characterization of Four-Arm Nanostructure Based on Ferromagnetic (Ga,Mn)As

Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

Electron Localization in Sb-Doped Si/SiGe Superlattices

Magnetotransport through Nanoconstriction in Ferromagnetic Semiconductor (Ga,Mn)As