<i>p</i>-type conduction mechanism in continuously varied non-stoichimetric SnO<i>x</i> thin films deposited by reactive sputtering with the impedance control
Junjun Jia, Takumi Sugane, Shin-ichi Nakamura, Yuzo Shigesato
Abstract
We successfully fabricated a series of SnOx films varying from SnO2 to SnO using reactive sputtering. By precisely tailoring the transition region in reactive sputtering, a continuous structural evolution from SnO2 to SnO was observed with SnO2 films showing a typical columnar structure and SnO films having a dense film structure with larger crystallites. X-ray diffraction measurement confirmed that the fabricated SnO films coexist with the minor SnO2 and Sn3O4 phases. SnO films exhibit an unintentional p-type conductivity, and the interstitial oxygen possibly acts as the acceptor. The maximum hole mobility is 3.38cm2/Vs at a hole concentration of 1.12×1018cm−3. We propose a p-type conduction mechanism for those SnOx films with the major SnO phase coexisting with the minor SnO2 and Sn3O4 phases, in which the possible optimum for the hole transport can be achieved by tailoring the balance between the amounts of the SnO2/Sn3O4 phases and interstitial oxygen.