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Báo cáo hóa học: " High degree of polarization of the near-bandedge photoluminescence in ZnO nanowires"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: High degree of polarization of the near-bandedge photoluminescence in ZnO nanowires | Jacopin et al. Nanoscale Research Letters 2011 6 501 http www.nanoscalereslett.eom content 6 1 501 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access High degree of polarization of the near-bandedge photoluminescence in ZnO nanowires 1 1 1 12 Gwenole Jacopin Lorenzo Rigutti Andres De Luna Bugallo Franpois Henry Julien Camilla Baratto Elisabetta Comini2 Matteo Ferroni2 and Maria Tchernycheva1 Abstract We investigated the polarization dependence of the near-band-edge photoluminescence in ZnO strain-free nanowires grown by vapor phase technique. The emission is polarized perpendicular to the nanowire axis with a large polarization ratio as high as 0.84 at 4.2 K and 0.63 at 300 K . The observed polarization ratio is explained in terms of selection rules for excitonic transitions derived from the k-p theory for ZnO. The temperature dependence of the polarization ratio evidences a gradual activation of the XC excitonic transition. PACS 78.55.Cr 77.22.Ej 81.07.Gf. Keywords zinc oxide nanowire photoluminescence polarization Introduction One-dimensional nanoscale semiconductors have recently attracted considerable attention as promising candidates for innovative device applications. Their high surface to volume ratio can be exploited for the development of a new generation of chemical and biological sensors 1-3 . The wide bandgap 3.37 eV of ZnO associated with its large exciton binding energy 60 meV also makes it one of the most promising materials for photonic devices such as light-emitting diodes 4 and lasers 5 . Thanks to the spatial separation of photogenerated carriers UV photodetectors with a very high photoconductive gain based on ZnO nanowires NWs have been demonstrated 6 . It has been shown that the photodetection properties of ZnO NWs depend on the light polarization 7 . The photoluminescence of ZnO is typically composed of a near-band-edge NBE peak due to excitonic recombination and of a broad emission band in the visible range related .