tailieunhanh - Báo cáo hóa học: " Enhanced UV photosensitivity from rapid thermal annealed vertically aligned 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: Enhanced UV photosensitivity from rapid thermal annealed vertically aligned ZnO nanowires | Dhara and Giri Nanoscale Research Letters 2011 6 504 http content 6 1 504 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Enhanced UV photosensitivity from rapid thermal annealed vertically aligned ZnO nanowires Soumen Dhara1 and PK Giri1 2 Abstract We report on the major improvement in UV photosensitivity and faster photoresponse from vertically aligned ZnO nanowires NWs by means of rapid thermal annealing RTA . The ZnO NWs were grown by vapor-liquid-solid method and subsequently RTA treated at 700 C and 800 C for 120 s. The UV photosensitivity photo-to-dark current ratio is X 103 for the as-grown NWs and after RTA treatment it is enhanced by a factor of five. The photocurrent PC spectra of the as-grown and RTA-treated NWs show a strong peak in the UV region and two other relatively weak peaks in the visible region. The photoresponse measurement shows a bi-exponential growth and bi-exponential decay of the PC from as-grown as well as RTA-treated ZnO NWs. The growth and decay time constants are reduced after the RTA treatment indicating a faster photoresponse. The dark current-voltage characteristics clearly show the presence of surface defects-related trap centers on the as-grown ZnO NWs and after RTA treatment it is significantly reduced. The RTA processing diminishes the surface defect-related trap centers and modifies the surface of the ZnO NWs resulting in enhanced PC and faster photoresponse. These results demonstrated the effectiveness of RTA processing for achieving improved photosensitivity of ZnO NWs. Keywords ZnO Nanowires rapid thermal annealing photocurrent photoresponse Introduction ZnO nanostructures NS such as nanowires NWs nanorods thinfilm etc. are extensively studied for their applications in various optoelectronic devices . UV photodetectors UV light emitting diodes phototransistors etc. 1-6 . However photodetection and photoconductivity of the ZnO NWs depends on the surface condition