Thin‐Film Cadmium Selenide Prepared from Cadmium Oxide Formed by Spray Pyrolysis

Abstract

Thin‐film cadmium selenide was prepared by a new process that involves two steps: (i) spray pyrolysis of an aqueous cadmium nitrate solution to form thin‐film cadmium oxide; and (ii) reaction of selenium vapor with cadmium oxide to form cadmium selenide. Composition data from proton‐induced x‐ray emission indicate that was converted completely to . Furthermore the process can be reversed completely by heating in air to form . The optical absorption spectra indicate that the bandgaps for the two materials are the same as those reported previously. The resistivity of all films is about 0.2 Ω‐cm, and the electron density is about 10¹⁹ cm⁻³. In contrast, the as‐prepared films have substantially higher resistivities (about 10⁸ Ω‐cm) and lower electron densities (about 10⁹ cm⁻³). However, by subsequent treatment of the film with cadmium vapor, the resistivity can be reduced to as low as 0.27 Ω‐cm with a corresponding increase in electron density to as high as 10¹⁹ cm⁻³, illustrating that a wide range of properties are possible for prepared by this technique.