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Abstract
The ultraviolet, visible and infrared properties of as-deposited and annealed Cu-SiO cermet thin films prepared by co-evaporation in vacuo at approximately 1 mPa in the thickness range 100-400 nm were investigated. The composition of copper was varied between 2-20vol%Cu. The evaluated optical band gap E opt varied between 2.71 and l.98eV over the composition range studied. A systematic reduction of E opt and an increase in the width of the band tailing E e were observed with increasing copper content. At 20°C, E opt for a fixed composition was found to increase with film thickness while the value of E e decreased. For annealed films, the absorption edges shifted towards shorter wavelength, with E opt, increasing and E e decreasing. The values of refractive index varied between 2.16 and 2.63, depending on film thickness and composition. The main infrared absorption band of the films was found at 1000cm−1. Electron diffraction and transmission electron microscopy revealed that the cermet structure consisted of crystalline Cu islands in an amorphous silicon monoxide matrix. The mean crystallite size increased with both increasing Cu content and substrate temperature.