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Bound Excitons (bound + exciton)
Selected AbstractsFeature Article: Bound exciton and donor,acceptor pair recombinations in ZnOPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2004B. K. Meyer The article [1] features the current state of knowledge on the optical properties of excitonic and donor,acceptor pair recombination in bulk n-ZnO, as revealed by recent photo- and cathodoluminescence measurements. The cover picture is a photograph showing an unusual look at the green luminescence of rod-shaped ZnO crystals under ultraviolet excitation. The first author, Bruno K. Meyer, is professor of physics at the Justus Liebig University of Giessen. His scientific interests include synthesis of semiconductor oxides by chemical vapour deposition and magnetron sputtering, in particular with respect to doping issues, materials science of electro- and thermochromic materials, recombination phenomena and defect characterization by magnetic resonance. This issue also contains an Editor's Choice on "Evolution of molecular ordering and phase transitions in C60/C70 solid solutions" by Gabriela Rueda-Morales and Jaime Ortiz-López [2]. [source] Mg-related acceptors in GaNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010B. Monemar Abstract Photoluminescence spectra of c -plane Mg doped GaN samples grown by MOVPE on bulk GaN templates reveal previously unknown properties, like the presence of several Mg-related acceptors. The use of unstrained samples allows a study of both bound exciton (BE) and donor-acceptor pair (DAP) spectra. Two main acceptors A1 and A2 are observed strongly in BE spectra as well as in DAP spectra, they have similar binding energies, i.e. about 220 meV. The common assignment of the deeper blue PL emission at 2.8,3.0 eV to a deep donor-shallow acceptor transition is questioned, and discussed in connection with the compensation problem in p-GaN. It seems like the Fermi level in p-GaN is controlled by a set of Mg-related acceptors at energies 0.2,0.6 eV from the valence band top. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and Optical Properties of Europium-Doped ZnS: Long-Lasting Phosphorescence from Aligned Nanowires,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2005C. Cheng Abstract Quasi-aligned Eu2+ -doped wurtzite ZnS nanowires on Au-coated Si wafers have been successfully synthesized by a vapor deposition method under a weakly reducing atmosphere. Compared with the undoped counterpart, incorporation of the dopant gives a modulated composition and crystal structure, which leads to a preferred growth of the nanowires along the [010] direction and a high density of defects in the nanowire hosts. The ion doping causes intense fluorescence and persistent phosphorescence in ZnS nanowires. The dopant Eu2+ ions form an isoelectronic acceptor level and yield a high density of bound excitons, which contribute to the appearance of the radiative recombination emission of the bound excitons and resonant Raman scattering at higher pumping intensity. Co-dopant Cl, ions can serve not only as donors, producing a donor,acceptor pair transition with the Eu2+ acceptor level, but can also form trap levels together with other defects, capture the photoionization electrons of Eu2+, and yield long-lasting (about 4,min), green phosphorescence. With decreasing synthesis time, the existence of more surface states in the nanowires forms a higher density of trap centers and changes the crystal-field strength around Eu2+. As a result, not only have an enhanced Eu2+ 4f65d1,4f7 intra-ion transition and a prolonged afterglow time been more effectively observed (by decreasing the nanowires' diameters), but also the Eu2+ related emissions are shifted to shorter wavelengths. [source] Photoluminescence studies of isotopically enriched siliconPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2003D. Karaiskaj Abstract We report the first high resolution photoluminescence studies of isotopically pure silicon. New information is obtained on isotopic effects on the indirect band gap energy, phonon energies, and phonon broadenings, which is in good agreement with previous results obtained in germanium and diamond. Remarkably, the line widths of the no-phonon boron and phosphorus bound exciton transitions in the 28Si sample (99.896% 28Si) are much sharper than in natural Si, revealing new fine structure in the boron bound exciton luminescence. Most surprisingly, the small splittings of the neutral acceptor ground state in natural Si are absent in the photoluminescence spectra of acceptor bound excitons in isotopically purified 28Si, demonstrating conclusively that they result from the randomness of the Si isotopic composition. [source] | ||||||||||