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

This manuscript first describes a simple synthesis of tungsten oxide (WOx) nanorods from templated W foil using a chemical vapour deposition (CVD) technique at 600-750 degrees C, then presents the formation of tungsten oxynitride (WOxNy) nanorods via nitridation at 650 degrees 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 WOx nanorods on the Au free areas. Consequently, following the oxide-to-nitride conversion, WOxNy nanorods were obtained with an identical patterned feature as to that of the parental WOx. Combined techniques including XRD, SEM, TEM and Raman were used to visualise and analyse the resulting WOx and WOxNy 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.