Growth, evolution and photocatalytic activity of ZnO nano back-tapered arrays

Abstract

Zinc oxide arrays of conical and hexagonal back-tapered nanocolumns with well-developed, flat and horizontal (0001) facets were synthesized on gold-coated (100) silicon substrates by a thermal evaporation process. Evolution of these conical and back-tapered structures was investigated by analysis of their morphological and chemical structures in different growth phases employing scanning electron microscopy, energy-dispersive X-ray spectroscopy and cathodoluminescence imaging. This study reveals that an ultrathin gold film predeposited on silicon is required to provide nucleation sites and form ZnO grains that progressively grow to vertical nanostructures. The growth process is assisted by carbonreduced zinc droplets deposited from the gas phase on the ZnO grains that evolve into back-tapered nanocanonical and hexagonal columns. These nanostructures are shown to be effective in the degradation of organic dyes. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.