Nitrogen doping of reactively sputtered tungsten oxide films

Tungsten trioxide (WO3) thin films are being developed for use in photoelectrochemical devices for solar water splitting, however the material's high bandgap limits device performance. Prompted by success with other metal oxides, bandgap modification of WO3 films through doping techniques is proposed. In this work, nitrogen doping was used to modify structural, optical, and electronic properties of the material. In a straightforward extension of the reactive-sputtering process, incorporating argon, oxygen, and nitrogen mixtures in the gas ambient, films were produced with measured bandgaps ranging from 3.0 down to 2.2 eV. Details of the modified films are discussed. (c) 2005 The Electrochemical Society.