Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 38: ZnO I
HL 38.2: Vortrag
Donnerstag, 29. März 2007, 10:15–10:30, H17
Origin of the near-band-edge photoluminescence in ZnO nanorods realised by vapour phase epitaxy and aqueous chemical growth — •C. Bekeny1, B. Hilker1, L. Wischmeier1, T. Voss1, B. Postels2, A. Mofor2, Andrey Bakin2, and A. Waag2 — 1IFP, University of Bremen, P.O Box 330440, 28334 Bremen — 2IHT, TU Braunschweig, P.O Box 3329, 38023 Braunschweig
Well established high temperature growth techniques like the vapour-liquid-solid (VLS: 1100°C) and vapour-phase-epitaxy (VPE: 800°C) have been successfully optimized while the low-temperature aqueous chemical growth (ACG: 90°C) is being extended to yield large-scale high quality ZnO nanorods. Here, a detailed and systematic photoluminescence (PL) study is presented to understand the microscopic processes responsible for the near-band-edge (NBE) emission in nanorods obtained from these processes. For the ACG samples, the as-grown nanorods show relatively broad NBE emission (15meV) attributed to the presence of large donor densities. After annealing in various atmospheres at ~800°C, a significant reduction of the linewidth (~4meV) and even the appearance of relatively sharp excitonic transitions is explained by the drastic reduction of the donor density. In contrast, the as-grown VPE and VLS samples exhibit well-resolved and sharp peaks resulting from exciton-related transitions. There is a shift in the room-temperature PL peak for VLS and VPE samples and is shown to result from contributions of the free exciton peak, its first and second order phonon replicas and not due to quantum confinement and or laser heating as assumed in literature.