Transparent p-type semiconductor: LaCuOS layered oxysulfide

La1-xSrxCuOS (x=0, 0.05) thin films prepared by radio-frequency sputtering were found to have high optical transmission (greater than or equal to 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 1.2x10(-2) and 2.6x10(-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. (C) 2000 American Institute of Physics. [S0003-6951(00)01343-7].