Nitrogen doping of nanoporous WO3 layers by NH3 treatment for increased visible light photoresponse

Nanoporous WO3 layers were grown by electrochemical anodization of W in a fluoride containing electrolyte. These layers were exposed to a thermal treatment in NH3 to achieve nitrogen doping of the material. The morphology, crystal structure, composition and photoresponse of pure and nitrogen doped WO3 were compared using scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. The results clearly show that successful nitrogen doping into WO3 layers can be achieved by controlling the temperature and time during the NH3 treatment. Most importantly, it is demonstrated that for the nitrogen doped WO3 layers the photocurrent is significantly enhanced in the visible light region.