Thin films which were deposited from chemical baths were intrinsic and highly photosensitive. They were converted here to n-type by the thermal diffusion of In from an evaporated 50nm In film that had been deposited onto the CdS film. This process, which occurred at temperatures of between 250 and 350C, involved the formation of an In2O3 surface layer which acted as a barrier and prevented the out-diffusion of In. This permitted the In to diffuse into the CdS film, and resulted in an In-doped CdS thin film.

P.J.George, A.Sánchez, P.K.Nair, M.T.S.Nair: Applied Physics Letters, 1995, 66[26], 3624-6