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Wyszukujesz frazę "Wójtowicz, G." wg kryterium: Autor


Tytuł:
Doping and Characterization of Wide-Gap II-VI Epilayers
Autorzy:
Karczewski, G.
Wojtowicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/1946648.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.Ln
71.55.-i
71.55.Gs
Opis:
In this paper we review the properties of n-type doped ZnSe and CdTe epilayers grown by molecular beam epitaxy on (100) GaAs substrates. Recent results of photoluminescence, transport measurements, secondary ion mass spectroscopy and deep-level transient spectroscopy are discussed. A major emphasis is placed on the effect of different dopant species and the role of the deviation from stoichiometry on the doped epitaxial layers. Since deep defect states play an important role in determining the properties of the doped materials, considerable attention is directed towards characterization and identification of deep-lying defect states, both native and introduced by dopants. In particular, in the case of ZnSe the deep-level transient spectroscopy results clarify why Cl is superior to Ga as an effective n-type dopant. They provide strong evidence that chlorine - unlike Ga - does not introduce by itself any detectable deep defects into the ZnSe lattice. In the case of CdTe, we focus on the influence of the deviation from stoichiometric growth conditions in the molecular beam epitaxy process and on the properties of In doped layers. We discuss resistivity, Mn diffusivity and the presence of various deep defects in layers grown at different Cd/Te flux ratios.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 635-644
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Weakly Diluted Magnetic CdTe/Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te Semiconductor Structures Grown by MBE
Autorzy:
Wojtowicz, Τ.
Karczewski, G.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933693.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
78.55.Et
Opis:
In this paper we review the results of our effort to grow layers and low-dimensional structures containing Cd$\text{}_{1-x}$Μn$\text{}_{x}$Te diluted magnetic semiconductor with relatively high values of Mn molar fraction x. A high quality of the structures grown so far is demonstrated by making use of results of several selected experiments. In the case of the epilayers having bulk-like thickness with x ≥ 0.7 we discuss, in particular, the magnetic phase diagram as well as we report on collective spin excitation (magnons) observed in Raman scattering experiments. The discussion of the growth of different quantum wells, including rectangular, digital, parabolic and wedge quantum wells, is accompanied by a brief overview of their optical and magnetooptical properties. These results include first measurements concerning magnetic polarons in quantum wells embedded in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te barriers with 0.4 ≤ x ≤ 0.8. Finally, we report on the present status of the search for dimensional effects in the spin-glass phase performed with the use of our specially designed superlattice structures.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 631-642
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Epitaxial Growths of II-VI Compounds on (110) Substrates
Autorzy:
Cywiński, G.
Wojtowicz, T.
Kopalko, K.
Karczewski, G.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1969044.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.-a
Opis:
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.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 281-284
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Search for T-Shaped Quantum Wires in CdTe/CdMg(Mn)Te System
Autorzy:
Cywiński, G.
Wojtowicz, T.
Karczewski, G.
Kossut, J.
Gębicki, W.
Powiązania:
https://bibliotekanauki.pl/articles/1969038.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.15.Rn
73.20.Dx
85.40.Ux
Opis:
We attempted to produce and to investigate T-shaped wire structures of II-VI compounds. Our samples were grown on GaAs hybrid substrates in a two-stage growth process. The photoluminescence measurements resulted into two different possible polarization behaviors of recorder signal. We interpret one of these behaviors as due to quantum wire formation.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 277-280
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graded Quantum Well Structures Made of Diluted Magnetic Semiconductors
Autorzy:
Wojtowicz, T.
Kutrowski, M.
Karczewski, G.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1968998.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
78.55.Et
Opis:
In this paper we review results of studies of two types of spatially graded quantum well structures containing various layers of diluted magnetic semiconductors Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te or Cd$\text{}_{1-x-y}$Mn$\text{}_{x}$Mg$\text{}_{y}$Te. The design of the structures has been recently proposed by us and suitable samples have been grown by a modified molecular beam epitaxy method. In the structures of the first type a digital profiling of the composition of the constituent material in the growth direction allowed to produce quantum wells with a specifically required shape of the confining potential (including parabolic, half-parabolic, triangular, and trapezoidal). Such samples were used for (i) determination of the conduction and valence band offsets in MnTe/CdTe and MgTe/CdTe systems, (ii) for the demonstration of an enhanced exciton binding in a parabolic confining potential as well as for (iii) demonstration of the possibility of "spin-splitting engineering" in diluted magnetic semiconductors quantum structures. In the second type of the structures, a precise in-plane profiling of either quantum well width or the barrier width or n-type doping intensity was realized. These structures were subsequently used for studies of the evolution of optical spectra with an increase in the concentration of confined two-dimensional gas of conduction electrons.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 199-217
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stimulated and Laser Emission in CdZnTe/CdMnTe Double Quantum Well Heterostructures
Autorzy:
Kowalczyk, L.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933829.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.45.+h
71.55.Gs
Opis:
Stimulated emission by optical excitation has been investigated in CdZnTe/CdMnTe quantum well heterostructures. Laser action has been achieved at 4.2 K and at 77 K with relatively low threshold values of the excitation intensity. Photοluminescence excitation spectra of the stimulated emission were obtained indicating that the optical gain involves exciton-exciton inelastic scattering.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 787-790
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrical Properties of p-ZnTe/n-CdTe Photodiodes
Autorzy:
Chusnutdinow, S.
Makhniy, V.
Wojtowicz, T.
Karczewski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1409588.pdf
Data publikacji:
2012-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.15.Hi
73.61.Ga
85.60.Dw
88.40.jm
Opis:
Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of photovoltaic, thinfilm p-ZnTe/n-CdTe heterojunctions have been studied in the temperature range of 280-400 K. The p-n junctions were grown by MBE on (100) semi-insulating GaAs substrates. From the analysis of I-V and C-V curves the potential barrier height of the junctions and its temperature dependence are determined. The relatively large value of the temperature coefficient of the potential barrier height (2.5-3.0 × $10^{-3}$ eV/K) indicates a high density of defects at the p-ZnTe/n-CdTe interface. The presence of interface defects limits the efficiency of the solar energy conversion of these devices.
Źródło:
Acta Physica Polonica A; 2012, 122, 6; 1077-1079
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Changing the Properties of the CdTe/ZnTe Quantum Dots by in situ Annealing during the Growth
Autorzy:
Wojnar, P.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/2047681.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.De
78.55.Et
Opis:
We present an attempt to control the properties of CdTe/ZnTe self-assembled quantum dots during their formation in the process of molecular beam epitaxy. Namely, the structures were in situ annealed at various temperatures and annealing times after the formation of quantum dots, before the deposition of a capping layer. Depending on the annealing parameters, the dots exhibit different optical properties which were studied by means of spatially resolved photoluminescence. From the analysis of these results, the information about relative changes of the average size and sheet density of quantum dots was extracted.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 283-288
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR Evidence for Thermally Excited Triplet States in Exinite, Vitrinite and Inertinite Separated from Bituminous Coal
Autorzy:
Słowik, G. P.
Wojtowicz, W.
Więckowski, A. B.
Powiązania:
https://bibliotekanauki.pl/articles/2043436.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Hq
76.30.Rn
87.64.Hd
Opis:
In this work we have made an electron spin resonance (EPR) study of macerals obtained from the lithotype clarain separated from Polish medium-rank coal (85.6 wt.% C). For three macerals:~exinite, vitrinite, and inertinite, the temperature dependence of intensity of EPR spectra in the temperature range of 100-373 K was investigated. The experimentally obtained EPR spectra of macerals were fitted by curves of the derivatives of the Gaussian and Lorentzian functions. The best fitting was obtained, when the experimental EPR spectra were assumed to be a superposition of three lines, for exinite and vitrinite - a broad Gaussian (G), a broad Lorentzian (L1) and a narrow Lorentzian (L3) line, but for inertinite of two lines - a narrow Lorentzian (L2) and a narrow Lorentzian (L3) line. The computer-assisted fitting has shown that each individual component line has similar values of resonance field, but different linewidths and amplitudes. The temperature dependence of line intensity I of the broad Gaussian (G) and narrow Lorentzian (L2 and L3) lines fulfils the Curie law in the form I=C/T or IT=C, whereas the broad Lorentzian (L1) line does not fulfil the Curie law. In the last case the temperature dependence of the Lorentzian (L1) component was fitted by the relation I=C/T+B/[T(3+exp(J/kT))] or IT=C+B/[3+exp(J/kT))], valid for thermally excited triplet states (S=1). For exinite and vitrinite the curves presenting the temperature dependence of the product IT versus temperature T were resolved into two curves, one for paramagnetic centres in the doublet state (S=1/2), and the other for paramagnetic centres in the thermally excited triplet state (S=1).
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 171-176
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ferroelectric Field Effect Transistor Based on Modulation Doped CdTe/CdMgTe Quantum Wells
Autorzy:
Kolkovsky, V.
Wojciechowski, T.
Wojtowicz, T.
Karczewski, G.
Powiązania:
https://bibliotekanauki.pl/articles/1811945.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.80.-e
77.80.Fm
85.50.Gk
73.61.Ga
Opis:
In this work, we observed effects of changing the electron concentration and electron mobility upon the poling of the $Cd_{0.96}Zn_{0.04}Te$ ferroelectric gate deposited on the top of the CdTe-based modulation doped quantum well structure, which are confirmation of the existence of the electrostatic field originating from the ferroelectric material, which can be controlled by an external voltage. The analysis of the data obtained from the Hall effect measurements showed that the electron mobility and carrier concentration decreased by a factor of 2.5 and 1.5, respectively upon the negative poling of the gate with respect to the poled by the positive voltage. Moreover, the electrostatic field, depending on its directions, causes depletion of accumulation of electrons in the 2D channel, i.e., it is a source of the field effect.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1173-1178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exciton Magnetic Polaron Features in Photoluminescence Excitation Spectra of CdTe/(CdMn)Te Quantum Wells with High Mn Contents
Autorzy:
Mackh, G.
Ossau, W.
Yakovlev, D. R.
Landwehr, G.
Wojtowicz, T.
Karczewski, G.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933923.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.+z
78.55.Et
Opis:
Exciton magnetic polarons are studied in CdTe/Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te (0.4 ≤ x ≤ 0.8) quantum wells. The magnetic polaron formation leads to the appearance of an additional line in the photoluminescence excitation spectra, which can be employed to determine the Zeeman splittings more exactly than by using the free exciton peak. We find an overall increase in the polaron energy with increasing x in the whole range of Mn contents studied.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 849-852
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
δ-Doped CdTe/Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te Multiple Quantum Wells Investigated by Photoreflectance Spectroscopy
Autorzy:
Sitarek, P.
Misiewicz, J.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933972.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.72.Vv
78.66.Hf
Opis:
Room temperature photoreflectance spectroscopy was used to investigate CdTe/Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te multiple quantum wells grown by MBE. Structures were indium δ-doped into the well or into the barrier. The value of heavy and light hole subbands splitting was measured and compared to the calculated ones. The influence of the position of δ-doping on the measured spectra was shown.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 901-904
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strain Relaxation of ZnTe/CdTe and CdTe/ZnTe heterostructures: In Situ Study
Autorzy:
Riesz, F.
Kret, S.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1952073.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.14.Hg
68.55.Bd
68.65.+g
Opis:
The strain relaxation kinetics of ZnTe/CdTe and CdTe/ZnTe heterostructures grown on GaAs substrates by molecular beam epitaxy are studied by in situ reflection high-energy electron diffraction. The observed critical layer thickness is 5 monolayers for ZnTe/CdTe and less than 1 monolayer for CdTe/ZnTe. The relaxation is anisotropic. Dislocation core parameters and relaxation rate constants were determined using a kinetic model and assuming strain-dependent activation energy of dislocation movement.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 911-914
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoluminescence of CdTe/CdMgTe Double Quantum Wells with a Two-Dimensional Electron Gas
Autorzy:
Deresz, M.
Wiater, M.
Karczewski, G.
Wojtowicz, T.
Łusakowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1033223.pdf
Data publikacji:
2017-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
CdTe/CdMgTe quantum wells
magnetophotoluminescence
Opis:
Magnetophotoluminescence measurements at liquid helium temperatures were carried out on asymmetric double quantum wells based on CdTe/CdMgTe heterostructures. Due to doping with shallow iodine donors, a two-dimensional electron gas was present in the quantum wells. The samples studied differed with the quantum well widths and doping level. We show a resemblance of the luminescence to results obtained on single quantum wells which suggests that in samples studied the quantum wells are not strongly coupled.
Źródło:
Acta Physica Polonica A; 2017, 132, 2; 390-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exciton Magneto-Optical Study on Single Quantum Wells, Cd$\text{}_{1-x}$Zn$\text{}_{x}$Te/Cd$\text{}_{1-x'-y}$Zn$\text{}_{x}$'Mn$\text{}_{y}$Te
Autorzy:
Takeyama, S.
Grabecki, G.
Adachi, S.
Takagi, Y.
Wojtowicz, T.
Karczewski, G.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1934045.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
78.20.Ls
78.66.Hf
Opis:
Four-single quantum wells composed of the ternary non-magnetic compounds Cd$\text{}_{0.93}$Zn$\text{}_{0.07}$Te (well width = 13, 19, 40, 90 Å), separated by the quaternary magnetic-compound Cd$\text{}_{0.48}$Zn$\text{}_{0.04}$Mn$\text{}_{0.48}$Te on (100)GaAs substrate were grown by MBE, and exhibited clear and distinctive photoluminescence lines corresponding to each quantum well. Double luminescence peaks with closely spaced within one well were observed from 90 Å and 40 Å quantum wells. Temperature and magnetic-field study revealed characteristic luminescence features associated with a bound exciton near the interface rather than with one monolayer fluctuation.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 945-948
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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