CdS thin films deposited from chemical bath containing citratocadmium(II) and thiourea are intrinsic and highly photosensitive. In the present letter, we discuss the conversion of such films to n type by thermal diffusion of indium from an evaporated 50 nm indium film deposited on the CdS thin film. The process which takes place in the temperature range of 250 °C–350 °C involves the formation of an In2O3 surface layer which acts as a barrier preventing the outdiffusion of indium. This allows indium to diffuse into the CdS film and results in an indium-doped CdS thin film. The electrical conductivity of such films is about 300 Ω−1 cm−1. All beneficial optical properties of chemically deposited CdS thin films for application as a window material in heterojunction optoelectronic devices are retained.
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George et al. (1995) studied this question.