Patterned growth of tungsten oxide and tungsten oxynitride nanorods from Au-coated W foil

Abstract

This manuscript first describes a simple synthesis of tungsten oxide (WO_x) nanorods from templated W foil using a chemical vapour deposition (CVD) technique at 600–750 °C, then presents the formation of tungsten oxynitride (WO_xN_y) nanorods via nitridation at 650 °C for different reaction times. The W foil, blade engraved, acid etched, or spin coated with Au-block copolymer composites then plasma etched, was used as a substrate for the nanorod growth. The Au patterns that were created on the surface of a W foil following the removal of the copolymer, led to a reverse patterned growth of WO_x nanorods on the Au free areas. Consequently, following the oxide-to-nitride conversion, WO_xN_y nanorods were obtained with an identical patterned feature as to that of the parental WO_x. Combined techniques including XRD, SEM, TEM and Raman were used to visualise and analyse the resulting WO_x and WO_xN_y nanorods. The diameter, length, and chemical composition of the nanorods are found to vary with reaction time and temperatures, as well as different substrate pre-treatments. This result represents a simple, innovative and efficient process for reverse-patterned growth of new nanomaterials.