Influence of sputtering ambient with hydrogen gas on optoelectrical properties of Ta-doped tin oxide

Abstract Ta-doped SnO 2 (TTO) is a suitable candidate to replace transparent conductive oxide (TCO) composed of expensive indium used for optoelectronics and silicon heterojunction solar cells fabricated below 200 °C. However, TTO films fabricated by sputtering at low temperature still demonstrate too high resistance and optical absorptance for application in industry. In this study, we investigate the influence of sputtering ambient on the optoelectrical properties of TTO films. The addition of hydrogen and oxygen to argon during sputtering leads to a large improvement in the optoelectrical properties of TTO films. The best TTO film has a low average absorptance of 1.9% and a low resistance of 3.8 × 10 −3 Ω⋅cm with a high carrier density of 9.3 × 10 19 cm −3 and mobility of 17.8 cm 2 ⋅V −1 ⋅s −1 . The microstructural and compositional properties of TTO films were characterized using x-ray diffraction, x-ray photoelectron spectroscopy and UV–Vis spectrophotometry. A proper ratio of hydrogen to oxygen in the sputtering gas improves the crystallinity and the doping efficiency of Ta. Optical absorptance is also reduced with suppressed formation of Sn(II) in the TTO films. Therefore, our findings exhibit remarkable potential for the industrial application of TTO as a low-cost TCO.