On the electrical conductivity of CdTe thin films evaporated onto unheated substrates

The electrical conductivity, σ, of CdTe semiconducting thin films (d=90–1200 nm) prepared by physical vapor deposition onto unheated glass substrates was investigated. Depending on the source temperature, films with (111) texture or an amorphous structure were obtained. At room temperature, the values of σ for as deposited films ranged from 10−6 to 10−4 Ω−1 m−1. The effects of source temperature and post-deposition heat treatment on the temperature dependence of the electrical conductivity of the films were studied. By in situ measurement of film resistivity during heating–cooling cycles, an irreversible dependence of σ was revealed for the films with amorphous structure. The results are discussed in relation with film recrystallization during the annealing process.