Photoluminescence and photomodulated transmittance spectroscopy of ZnO nanowires

Abstract

Abstract ZnO nanowires have been synthesized by a simple vapor transport method of heating the mixture of zinc oxide and carbon powders in an open tube of the furnace. The scanning‐electron‐microscopy images show that the average diameters of the nanowires deposited on quartz substrates for t = 20 and 40 min are ∼20 and ∼40 nm, respectively. Low‐temperature (77 K) photoluminescence (PL) spectrum in ZnO nanowires shows a sharp emission at 3.36 eV due to excitons bound to neutral donors. Spectral analysis also suggests a peak of biexciton emission at ∼3.35 eV. The biexciton binding energy determined here is ∼17 meV, in agreement with previous results. Photomodulated transmittance (PT) spectroscopy has been used to investigate the E 0 critical‐point structures in ZnO nanowires. The measured PT spectrum shows distinct structures at ∼3.3–3.5 eV. These structures are found to be mainly due to excitonic transitions at the E 0 edge. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)