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1
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Liquid Nitrogen and Room Temperature Reflectivity Spectra of Cd_{1-x}Fe_{x}Se in the 0.5-6.0 eV Energy Range

100%
Dębowska D., Zimnal-Starnawska M., Kisiel A., Giriat W.
Acta Physica Polonica A
|
1994
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vol. 86
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issue 6
1015-1020
EN
The reflectivity measurements for mixed crystals Cd_{1-x}Fe_{x}Se (0.00 ≤ x ≤ 0.10) have been carried out in an energy range of 0.5-6.0 eV at 300 and 77 K. The influence of Fe^{2+}(3d^{6}) states on the changes in the energy positions of the reflectivity maxima E_{0}, E_{1}(A_{1}), E_{1}(A_{2}), and E_{1}(B) is analyzed and the obtained results are consistent with the models existing in the literature.
2
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Transition Metal Impurities and Electronic Structure of ZnSe-Based Isovalent Semiconductor Alloys

100%
Surkova T. P., Giriat W., Godlewski M., Permogorov S.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
1009-1012
EN
Energy level positions of the nickel 2+/1+ and cobalt 2+/3+ charge states have been used to estimate band edges for the valence and conduction bands of ZnSe-based alloys with cation (ZnCdSe) and anion (ZnSSe) substitution. Chemical trends in band offsets of heterostructures of Zn- or Mn-based II-VI compounds are analysed. Further on, the change of Ni^{2+}(3d^{8}) and Co^{2+}(3d^{7}) intra-d shell transition bands upon the alloying of host material is discussed.
3
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X-Ray Absorption Near Edge Structure Analysis of HgMnSe, HgFeSe and HgTeSe

88%
Burattini E., Kisiel A., Markowski R., Dalba G., Giriat W.
Acta Physica Polonica A
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1993
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vol. 83
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issue 1
107-114
EN
Experimental studies of the Se K X-ray absorption edges have been carried out in HgTe_{0.5}Se_{0.5}, Hg_{0.8}Mn_{0.2}Se and Hg_{0.9}Fe_{0.1}Se. A comparison is made for Hg_{0.5}Mn_{0.5}Se and Hg_{0.5}Fe_{0.5}Se theoretical results obtained by the self-consistent, semi-relativistic LMTO method within the LD approximation. Small differences of Se K edge XANES have been shown for HgTeSe and HgSe in contrary to evident differences for HgMnSe and HgFeSe. This behaviour of the absorption Se K edges is related to significant, hybridized contribution of the 3d and 4s Mn or Fe unoccupied states. The maximal contributions of the hybridized bands of the hypothetic zinc-blende MnSe or FeSe were estimated using the virtual crystal model. These maximal contributions are situated at about 6 eV and 17 eV in zinc-blende MnSe and at -0.8 eV and 5.5 eV in zinc-blende FeSe. For HgFeSe apart from the evidence of the strongly localized resonant donor (empty for low Fe concentrations) the complementary hybridized contribution of Fe 3d empty states also situated around the conduction band minimum should be taken into consideration.
4
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Magnetization and Susceptibility of Cd_{1-x}Co_{x}Se

88%
Górska M., Anderson J., Green S., Kido G., Giriat W.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
753-756
EN
The magnetization and magnetic susceptibility of Bridgman-grown Cd_{1-x}Co_{x}Se with values of x up to 0.04 have been measured over a temperature range from 2 to 390 K and in magnetic fields up to 23 T. A pair-exchange value J/k_{B} of about -3 K was obtained from the magnetic field dependence of the magnetization. This exchange is probably due to the next-nearest-neighbor interaction. The high-temperature susceptibility data indicated a presence of the Curie-Weiss like paramagnetism and the temperature independent Van Vleck type paramagnetism.
5
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Room and Liquid Nitrogen Temperature Reflectivity Spectra of Co,Se Mixed Crystals

76%
Dębowska D., Zimnal-Starnawska M., Kisiel A., Piacentini M., Zema N., Lama F., Giriat W.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
275-278
EN
The optical properties of the semiconducting compounds Zn_{1-x}Co_{x}Se crystallizing in the zinc-blende structure have been investigated. The reflectivity spectra of these materials for different concentration of Co ions, have been taken out in a wide energy range between 4 and 25 eV at room (RT) and liquid nitrogen temperature (LNT) using synchrotron radiation from ADONE Storage Ring in Frascati. The comparisons between the reflectivity spectra of ternary systems and host crystal ZnSe are made. On the basis of the experimental and theoretical results, the changes of the structures of the reflectivity spectra of host crystal ZnSe caused by the influence of transition metal ions are discussed.
6
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Liquid Nitrogen Temperature Reflectivity Spectra of Zn_{1-x}Mn_{x}Se and Zn_{1-y}Fe_{y}Se Mixed Crystals

76%
Zimnal-Starnawska M., Dębowska D., Kisiel A., Piacentini M., Lama F., Zema N., Giriat W.
Acta Physica Polonica A
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1994
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vol. 86
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issue 5
869-874
EN
The liquid nitrogen temperature reflectivity spectra of the tetrahedral diluted magnetic semiconductors (DMS's) Zn_{1-y}Fe_{y}Se and Zn_{1-x}Mn_{x}Se crystallizing in the zinc-blende structure were investigated. The reflectivity measurements for different concentration of Fe (y = 0.01, 0.05, and 0.10) and Mn (x = 0.10 and 0.30) ions were taken out in a wide energy range between 4 and 30 eV using synchrotron radiation from ADONE storage ring in Frascati. The average resolution ΔE/E used for these measurements was better than 1 × 10^{-3} over the entire spectral range. The single crystals were cleaved, before being mounted inside the reflectometer, from the samples grown by the Bridgman method. The comparison between the reflectivity spectra of ternary systems and host crystal ZnSe is made. The changes of the structures of reflectivity spectra of host crystal ZnSe caused by the influence of Fe and Mn ions are discussed.
7
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EXAFS Studies of Zn_{1-x}Mn_{x}S Ternary Compounds

76%
Zimnal-Starnawska M., Łażewski J., Kisiel A., Boscherini F., Pascareli S., Giriat W.
Acta Physica Polonica A
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1994
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vol. 86
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issue 5
763-766
EN
We performed extended X-ray absorption fine structure (EXAFS) measurements of Zn_{1-x}Mn_{x}S solid solution for various concentrations x in the range of 0 ≤ x ≤ 0.4. Data were collected on Zn and Mn K-edges with the use of synchrotron radiation from the ADONE storage ring in Frascati utilizing the Si(111) channel-cut monochromator. Applying the usual procedure of data reduction described elsewhere, we found well-defined different nearest-neighbor Zn-S and Mn-S distances, according to the previous results, almost independent on x. For Mn-S distances in the range of 0.1 ≤ x ≤ 1.0 we found, within the limit of experimental error, a constant value equal to 2.430±0.008 Å. For Zn-S distances for concentration changing from x = 0.0 to x = 0.4 we observed a weak, linear increase from 2.343±0.008 Å to 2.354 ± 0.008 Å, respectively.
8
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Vacuum Ultraviolet Reflectivity of Cd_{1-x}Fe_{x}Te

76%
Dębowska D., Zimnal-Starnawska M., Kisiel A., Piacentini M., Zema N., Giriat W.
|
EN
Reflectivity spectra for mixed crystals Cd_{1-x}Fe_{x}Te with 0.00 ≤ x ≤0.05 were investigated. The measurements were carried out in the energy range 6.0-30.0 eV at 300 K. The influence of Fe^{2+}(3d^{6}) states on the changes in the energy positions of the reflectivity maxima E'_{1} , E'_{1} + ∆, c, d, e, f, h and i is analysed. The obtained results confirm the band structure diagrams published previously.
9
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Co^{2+} Ions in ZnS_{x}Se_{1-x}:Co - ESR and Optical Studies

76%
Świątek K., Surkova T., Sienkiewicz A., Zakrzewski A., Godlewski M., Giriat W.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
593-596
EN
The electron spin resonance of Co^{2+} ions in ZnS_{x}Se_{1-x}:Co mixed crystals was measured at temperature of 3 K and microwave frequency of 9.47 GHz. Trigonal Co_{Zn}^{2+}-S center in the ZnS_{0.001}Se_{0.999}:Co crystal was identified and parameters of relevant spin Hamiltonian were determined. Influence of alloy disorder in the anion sublattice on the Co_{Zn}^{2+} ground and first excited states is briefly discussed.
10
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Energy Level Position of Ni and Band Offsets in Zn_{1-x}Cd_{x}Sc:Ni and ZnS_{x}Sc_{1-x}:Ni

76%
Surkova T., Giriat W., Godlewski M., Kaczor P., Zakrzewski A. J., Permogorov S., Tenishev L.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
925-928
EN
Absorption and reflectivity measurements have been carried out for Zn_{1-x}Cd_{x}Se:Ni and ZnS_{x}Se_{1-x}:Ni solid solutions. Energy level positions of nickel 2+/1+ charge state have been used for estimation of band offsets for the valence and conduction bands of ZnCdSe/ZnSe and ZnSSe/ZnSe. Intra-shell transitions of Ni^{2+} were also studied.
11
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Photoluminescence of Co-Doped ZnCdSe and ZnSSe Alloys

64%
Surkova T., Born H., Thurian P., Hoffmann A., Busse W., Gumlich H., Broser I., Giriat W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
1013-1016
EN
Photoluminescence measurements have been carried out for Zn_{1-x} Cd_{x} Se:Co and ZnS_{x}Se_{1-x}:Co mixed crystals. Changes of recombination channels are observed in mixed crystals as compared to the emission of host binary compounds. Character of changes is slightly different for the alloys with cation and anion substitution. Photoluminescence kinetics of the L-line and of two other Co^{2+} intra-shell emission bands was measured to determine radiative decay rates.
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