Synthesis of large-area and aligned copper oxide nanowires from copper thin film on siliconsubstrate

Abstract

Large-area and aligned copper oxide nanowires have been synthesized by thermalannealing of copper thin films deposited onto silicon substrate. The effects of the filmdeposition method, annealing temperature, film thickness, annealing gas, andpatterning by photolithography are systematically investigated. Long and alignednanowires can only be formed within a narrow temperature range from 400 to500 °C. Electroplated copper film is favourable for the nanowire growth, comparedto that deposited by thermal evaporation. Annealing copper thin film instatic air produces large-area, uniform, but not well vertically alignednanowires along the thin film surface. Annealing copper thin film under aN2/O2 gas flow generates vertically aligned, but not very uniform nanowires onlarge areas. Patterning copper thin film by photolithography helps tosynthesize large-area, uniform, and vertically aligned nanowires along thefilm surface. The copper thin film is converted into bicrystal CuO nanowires,Cu2O film, and also perhaps some CuO film after the thermal treatment in static air. Only CuO in theform of bicrystal nanowires and thin film is observed after the copper thin film is annealed under aN2/O2 gas flow.