Extraordinarily high ultraviolet photosensitivity and sharp cut off wavelength of hydrothermally grown zinc oxide nanorods

Abstract

Low temperature solution growth of ZnO nanostructures carries immense technological importance. Vertically aligned ZnO nanorods (NRs) arrays have been grown on glass substrate at low temperature using zinc acetate di-hydrate, hexamethelene tetramine (HMT) and cetyl-trimethyl amonium bromide (CTAB) and their ultraviolet (UV) photosensitivity properties have been investigated. Hydrothermally grown ZnO NRs arrays show a very high UV-to-visible rejection ratio (112) with a sharp cut-off wave length at 400 nm in the photocurrent spectrum as compared to ZnO NRs grown by another low temperature technique using aqueous chemical growth (ACG) method. The hydrothermal NRs show extraordinarily high UV photosensitivity (photo-to-dark current ratio, 1.16×105) which is nearly one order of magnitude higher than that of ACG NRs. Analyses of growth-decay time constants, photoluminescence spectra, full width at half maximum for (002) x-ray diffraction peak indicate better crystalline quality which is responsible for the high rejection ratio, sharp cut-off wavelength and faster growth decay constants in the hydrothermal NRs.