Preparation of [formula omitted] thin films by activated reactive evaporation technique

Abstract

Thin films of cuprous sulphide (Cu 2S) have been deposited for the first time by a novel Activated Reactive Evaporation (ARE) technique. These films have been deposited as a function of various deposition conditions such as partial pressure of hydrogen sulphide gas, substrate temperature and copper evaporation rate. The microstructure of the films have been characterized by optical microscopy, transmission electron microscopy and electron diffraction. Electrical and optical characterization has also been carried out. Films deposited using, a H 2S partial pressure in the range from 10 −2 to 8 × 10 −4 Torr . a substrate temperature at or near room temperature and a copper evaporation rate of about 200 Å/min, were found to consist of pure chalcocite (Cu 2S). Electrical and optical measurements of the pure Cu 2S films indicated that these films were p-type with carrier concentrations of 1–7 × 10 20/ cm 3 and typical mobility values of 1–3 cm 2/V s. Mobilities as high as 8 cm 2/v s were measured on some samples. The optical determination of the band gap gave a value of E g ≈ 1.2 eV . Preliminary investigation of the Cu 2S/CdS heterojunctions were also carried out usin ARE deposited Cu 2S films on CdS films prepared by direct evaporation.