Influence of oxygen flow rate on microstructural, electrical and optical properties of indium tin tantalum oxide films

Indium tin oxide (ITO) and indium tin tantalum oxide (ITTO) films were deposited on glass substrates by magnetron sputtering technology with one or two targets. Properties of ITO and ITTO films deposited at different oxygen flow rates were contrastively studied. Ta-doping strengthens along the orientation of (400) plane and leads to better crystalline structure as well as to a decrease in surface roughness. The increase in oxygen flow rate increases sheet resistance and reduces carrier concentration, and ITTO films show higher carrier concentration. Certain oxygen flow rates can improve the visible light transmittance of films, but excessive oxygen can worsen the optical properties. The carrier concentration has an important influence on near-IR reflection, near-UV absorption and optical band gap. The optical band gap decreases with the increasing of oxygen flow rate, and ITTO films show wider optical band gap than ITO films. ITTO films prepared by co-sputtering reveal better optical–electrical properties and chemical and thermal stability than ITO films.