Transparent <i>p</i>-type semiconductor: LaCuOS layered oxysulfide

Abstract

La 1−x Sr x CuOS (x=0, 0.05) thin films prepared by radio-frequency sputtering were found to have high optical transmission (⩾70%) at the visible and near-infrared wavelengths and an energy gap of about 3.1 eV. The dc electrical conductivities of x=0 and 0.05 thin films at room temperature were 1.2×10−2 and 2.6×10−1 S cm−1, respectively. The Seebeck coefficients of these samples were positive, indicating that p-type electrical conduction is dominant in these materials. A sharp photoluminescence peak, probably originating from an interband transition, was observed at the optical absorption edge. The present study demonstrates that LaCuOS is a promising transparent p-type semiconductor for optoelectronic applications. Moreover, our material design, based on chemical modulation of the valence band, was successfully extended to oxysulfide systems.