Influence of selenization temperature on synthesis, morphology, and properties of nanostructured CoSe2 films

Nanostructured cobalt selenide (CoSe2) thin films were deposited on a glass substrate using the selenization of Co films at different selenization temperatures (300 °C, 400 °C, and 500 °C) in a pure Se vapor for two hours. The morphology and structure of the as-deposited films shows that the film morphology and crystallinity are affected by the selenization temperature. Increasing the selenization temperature from 300 °C to 400 °C and 500 °C results in a change in the surface and cross sectional morphology. At 300 °C, the Co films have an almost amorphous structure, while at temperatures of 400 and 500 °C, the Co films have a crystalline nanostructure with bilayered morphology. Optical analyses of the CoSe2 films at 500 °C show a large absorption (α > 1.0 × 105 cm−1) and a direct band gap (∼1.0 eV).