Electrical and Optical Properties of Layered Oxysulfides with CuS Layers: Sr−Cu−M−O−S System (M = Zn, Ga, In)

The electrical and optical properties of layered oxysulfides (Sr−Cu−M−O−S system (M = Zn, Ga, In)), which have common CuS layers, were studied to examine their potential as wide-gap p-type semiconductors. The attempts of electrical conductivity control by Na doping demonstrated that the conductivities of the Sr2-xNaxCu2ZnO2S2 (σ = 2.2 × 10-8 S cm-1 for x = 0.0) and Sr2-xNaxCuGaO3S (σ = 2.2 × 10-4 S cm-1 for x = 0.0) at room temperature increased up to 1.2 × 10-1 and 2.4 × 10-2 S cm-1 for x = 0.1, respectively, with an increase in Na concentration. In addition, both Hall and Seebeck measurements proved that these conductive oxysulfides were p-type semiconductors. The diffuse reflectance spectra of the materials revealed that the optical absorption edges were approximately 450 nm for Sr2Cu2ZnO2S2, 480 nm for Sr2CuGaO3S, and 540 nm for Sr2CuInO3S. It became evident from these results that the layered oxysulfides (Sr−Cu−M−O−S system (M = Zn, Ga, In)) were wide-gap p-type semiconductors utilizing the CuS layer...