| 1. |
- Adcox, K, et al.
(författare)
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PHENIX detector overview
- 2003
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 499:2-3, s. 469-479
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX detector is designed to perform a broad study of A-A, p-A, and p-p collisions to investigate nuclear matter under extreme conditions. A wide variety of probes, sensitive to all timescales, are used to study systematic variations with species and energy as well as to measure the spin structure of the nucleon. Designing for the needs of the heavy-ion and polarized-proton programs has produced a detector with unparalleled capabilities. PHENIX measures electron and muon pairs, photons, and hadrons with excellent energy and momentum resolution. The detector consists of a large number of subsystems that are discussed in other papers in this volume. The overall design parameters of the detector are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Valakh, M.Ya., et al.
(författare)
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Optical investigation of CdSe/ZnSe quantum nanostructures
- 2002
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 17:2, s. 173-177
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Tidskriftsartikel (refereegranskat)abstract
- We have used resonant and non-resonant Raman scattering as well as photoluminescence and cathodoluminescence experiments to study the structure and composition properties of CdxZn1-xSe formed by migration enhanced epitaxy of CdSe layers on ZnSe buffers. The spectral change of the photoluminescence maximum correlates with the increase of the Cd content, depending on the nominal CdSe thickness in the 1.5-3.0 ML range. The inhomogeneous broadening of the photoluminescence band is caused by the composition difference between the two-dimensional mixed CdxZn1-xSe layer and the inserted islands with larger Cd concentration. This is confirmed by phonon frequency changes in resonant Raman scattering for samples with different nominal CdSe thicknesses as well as in Stokes and anti-Stokes frequency changes observed in the 1.5 ML sample. Attention is paid to the role of defects on Raman scattering and photoluminescence for the 3.15 ML sample.
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| 3. |
- Ivanov, S.V., et al.
(författare)
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MBE growth and properties of bulk BeCdSe alloys and digital (BeSe : CdSe)/ZnSe quantum wells
- 2000
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 214, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- We report for the first time on MBE growth, structural and optical properties of single layers, quantum well structures and short-period superlattices based on BexCd1-xSe ternary alloys on GaAs. Both the conventional MBE growth mode and the sub-monolayer digital alloying technique (SDA) have been employed for the fabrication of the structures. Compositional boundaries of an instability region 0.03 < x < 0.38, calculated in a regular solution approximation for the completely coherent system, agree well with available experimental data. A suppression of the phase separation in BeCdSe by elastic stress in the layer, accompanied by a strong reduction of the Cd incorporation coefficient has been found. Ultrathin 2.8 ML BeCdSe SDA QWs with x approx. 0.15 demonstrate about an order of magnitude increase in the PL intensity with respect to the pure CdSe one, probably resulting from an enhanced carrier localization efficiency. Eg as a function of the Be content reveals a strong bowing in optical data, which allows one to consider BeCdSe alloys with compositions nearly lattice-matched to GaAs as potential materials for the active region of blue-green lasers.
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| 4. |
- Lebedev, A.A., et al.
(författare)
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Radiation hardness of wide-gap semiconductors (using the example of silicon carbide)
- 2002
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Ingår i: Semiconductors (Woodbury, N.Y.). - : Pleiades Publishing Ltd. - 1063-7826 .- 1090-6479. ; 36:11, s. 1270-1275
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Tidskriftsartikel (refereegranskat)abstract
- Results obtained in studying the effect of ionizing radiation on epitaxial layers and devices based on silicon carbide (SiC) are considered. It is shown that, in investigations of wide-gap semiconductors (WGS), account should be taken of how the rate of removal of mobile charge carriers - the standard parameter in determining the radiation hardness of a material - depends on temperature. The use of data obtained only at room temperature may lead to an incorrect assessment of the radiation hardness of WGS. A conclusion is made that the WGS properties combine, on the one hand, high radiation hardness of high-temperature devices based on these semiconductors and, on the other, the possibility of effective radiation-induced doping (e.g., for obtaining semi-insulating local regions in a material at room temperature). © 2002 MAIK "Nauka/Interperiodica".
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| 5. |
- Toropov, A.A., et al.
(författare)
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Excitons as a probe of interface morphology in Cd(Zn)Se/ZnSe heterostructures
- 2000
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 166:1, s. 278-283
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Tidskriftsartikel (refereegranskat)abstract
- We present studies of the excitonic spectrum in superlattices (SLs) of CdSe insertions in a ZnSe matrix aimed at elucidating the CdSe/ZnSe interface morphology. The experimental photoluminescence excitation spectra are compared with the results of variational exciton calculations performed within the effective mass approximation. The shape of the average vertical (along the SL growth axis) distribution of CdSe within each insertion, used in the calculations, was obtained from a theoretical simulation of X-ray diffraction (XRD) rocking curves measured in the same samples. The results indicate that the thinnest layers are graded composition ZnCdSe quantum wells (QWs), generally homogeneous in the layer planes, whereas flat islands enriched by Cd appear at the CdSe nominal thickness larger than 0.5-0.6 monolayer (ML).
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| 6. |
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| 7. |
- Moskvin, O V, et al.
(författare)
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Carbonic anhydrase activities in pea thylakoids. : A photosystem II core complex-associated carbonic anhydrase
- 2004
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Ingår i: Photosynthesis Research. - 0166-8595. ; 79:1, s. 93-100
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Tidskriftsartikel (refereegranskat)abstract
- Pea thylakoids with high carbonic anhydrase (CA) activity (average rates of 5000 µmol H+ (mg Chl)–1 h–1 at pH 7.0) were prepared. Western blot analysis using antibodies raised against the soluble stromal beta-CA from spinach clearly showed that this activity is not a result of contamination of the thylakoids with the stromal CA but is derived from a thylakoid membrane-associated CA. Increase of the CA activity after partial membrane disintegration by detergent treatment, freezing or sonication implies the location of the CA in the thylakoid interior. Salt treatment of thylakoids demonstrated that while one part of the initial enzyme activity is easily soluble, the rest of it appears to be tightly associated with the membrane. CA activity being measured as HCO3 – dehydration (dehydrase activity) in Photosystem II particles (BBY) was variable and usually low. The highest and most reproducible activities (approximately 2000 µmol H+ (mg Chl)–1 h–1) were observed in the presence of detergents (Triton X-100 or n-octyl-beta-D-glucopyranoside) in low concentrations. The dehydrase CA activity of BBY particles was more sensitive to the lipophilic CA inhibitor, ethoxyzolamide, than to the hydrophilic CA inhibitor, acetazolamide. CA activity was detected in PS II core complexes with average rate of 13,000 µmol H+ (mg Chl)–1 h–1 which was comparable to CA activity in BBY particles normalized on a PS II reaction center basis.
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| 8. |
- Shubina, Tatiana, et al.
(författare)
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Optical properties of GaN/AlGaN quantum wells with inversion domains
- 2003
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Ingår i: Physica status solidi. A, Applied research. - : Wiley. - 0031-8965 .- 1521-396X. ; 195:3, s. 537-542
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Tidskriftsartikel (refereegranskat)abstract
- Two-band photoluminescence (PL) and respective absorption and reflection features are observed in GaN/AlGaN MBE-grown quantum well (QW) structures of dominant N polarity with inversion domains (IDs). The PL bands are related to transitions in the regions of different polarity, characterized by different strain and electric fields. A micro-PL study reveals sharp and narrow (1.5-2.5 meV) PL lines placed between the bands, which are tentatively attributed to recombination at localization sites associated with intersections of the QWs with the domains. Additionally, we demonstrate that the ID formation decreases the overall strength of the intrinsic electric fields in the QW structures.
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| 9. |
- Tkachman, M.G., et al.
(författare)
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Phonon-assisted exciton luminescence in GaN layers grown by MBE and chloride-hydride VPE
- 2003
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Ingår i: Semiconductors (Woodbury, N.Y.). - : Pleiades Publishing Ltd. - 1063-7826 .- 1090-6479. ; 37:5, s. 532-536
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Tidskriftsartikel (refereegranskat)abstract
- Optical properties of GaN layers grown by the molecular-beam epitaxy (MBE) and chloride-hydride vapor-phase epitaxy (CHVPE) have been studied, and the quality of two types of samples has been compared. The photoluminescence spectra have an excitonic nature for both types of layers. To determine precisely the nature of exciton transitions, the reflectance spectra were studied. A key point was the investigation of phonon-assisted exciton luminescence, which provides information on the density distribution of the exciton states. Temperature dependences of the exciton transition energy and the ratio of intensities of one- and two-phpnon replicas were studied. The high quality of both types of layers has been confirmed, though the concentration of acceptors in MBE-grown samples is higher than in CHVPE samples. © 2003 MAIK "Nauka/Interperiodica".
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| 10. |
- Donchev, V., et al.
(författare)
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High-temperature excitons in GaAs quantum wells embedded in AlAs/GaAs superlattices
- 2000
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 58:2, s. 478-484
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Tidskriftsartikel (refereegranskat)abstract
- Photoluminescence (PL) spectra of GaAs quantum wells embedded in short-period AlAs/GaAs superlattices have been measured at 2 K and at room temperature. Two approaches have been applied in order to investigate the mechanisms of radiative recombination in these structures. In the first one, we studied the excitation density dependence of the PL intensity. In the second approach a line-shape analysis of the PL spectra is performed by means of a statistical model, which includes both free exciton, and free carrier recombinations. The fit based on this model reproduces with high accuracy the experimental spectra and allows to assess the relative contributions of excitons and free carriers to the radiative recombination process. The results of both approaches indicate the predominance of free excitons in the radiative recombination at room temperature.
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