Surface effects and nonlinear optical properties of ZnO nanowires

This paper discusses the surface effects and nonlinear optical properties of ZnO nanowires. First, the influence of the large surface-to-volume ratio of the nanowires on their photoluminescence properties is shown. The occurrence of a surface-exciton emission line is demonstrated and its properties are studied in time-integrated and time-resolved photoluminescence measurements. It is further demonstrated that this band is sensitive to surface modifications of the nanowires, such as dielectric and metallic coatings. It is shown that hydrogen can passivate deep defects in ZnO nanowires thereby reducing the defect luminescence and strongly enhancing the near-bandedge excitonic luminescence. The photoluminescence properties of chemically synthesized ZnO nanowires are compared to those of nanowires grown by vapor-transport techniques. The non-linear coefficients of chemically synthesized nanowires are analyzed, and first preliminary measurements of the optical gain of a ZnO nanowire waveguide are analyzed. [GRAPHICS] (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim