tailieunhanh - Báo cáo hóa học: " Ultrafast hole carrier relaxation dynamics in p-type CuO nanowires"

Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Ultrafast hole carrier relaxation dynamics in p-type CuO nanowires | Othonos and Zervos Nanoscale Research Letters 2011 6 622 http content 6 1 622 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Ultrafast hole carrier relaxation dynamics in p-type CuO nanowires Andreas Othonos1 and Matthew Zervos2 Abstract Ultrafast hole carrier relaxation dynamics in CuO nanowires have been investigated using transient absorption spectroscopy. Following femtosecond pulse excitation in a non-collinear pump-probe configuration a combination of non-degenerate transmission and reflection measurements reveal initial ultrafast state filling dynamics independent of the probing photon energy. This behavior is attributed to the occupation of states by photogenerated carriers in the intrinsic hole region of the p-type CuO nanowires located near the top of the valence band. Intensity measurements indicate an upper fluence threshold of 40 pJ cm2 where carrier relaxation is mainly governed by the hole dynamics. The fast relaxation of the photo-generated carriers was determined to follow a double exponential decay with time constants of ps and ps. Furthermore time-correlated single photon counting measurements provide evidence of three exponential relaxation channels on the nanosecond timescale. Keywords CuO nanowires pump-probe spectroscopy carrier dynamics Introduction Low-dimensional semiconductor nanostructures have been an active field of research due to their fascinating physical properties which are very different from their bulk counterparts. An important class of such nanostructures are semiconductor nanowires NWs since they may be used as building blocks for electronic and photonic devices which have attracted a great deal of attention over the past few years 1-3 . So far a broad variety of metal-oxide MO NWs such as ZnO SnO2 In2O3 and Ga2O3 have been grown and investigated in view of their potential technological applications. However most of these MO NWs are n-type due to donors like .