Cadmium selenide film through ammonia free thermal substitution reaction on cadmium oxide hydroxide films by chemical vapor deposition

• CVD process with Se gas is used to convert Cd(O2)0.8(OH)0.2 to CdSe films.
• CdSe polycrystalline films obtained have good crystalline quality.
• The film show a hexagonal crystalline phase whith 1.7 eV energy band gap.
• CdSe film thickness up to 20 μm with hexagonal-shaped grains were obtained.
• Grain size of 2–3 μm were attained after 30 min of CVD substitution process.

Polycrystalline CdSe films with hexagonal phase were deposited on glass substrates by thermal substitution reaction in a CVD reactor. The films were prepared in two stages. First, films of cadmium oxide hydroxide Cd(O2)0.88(OH)0.24 were deposited on the glass substrates by chemical bath deposition (CBD), using ammonia free, low temperature process in alkaline aqueous solution. Then the CBD-deposited films were placed in a Chemical Vapor Deposition (CVD) Hot Wall reactor where they acted as precursors in a reaction of substitution of non-metallic film component by Se, thus forming CdSe semiconductor films. The Se gas was transported from the source to the substrate with a nitrogen flux of 0.25 l/min. The chalcogen source temperature was 500 °C, which is above the melting point (217 °C) but below the boiling point of Se (684.9 °C). The substrate temperature was adjusted to obtain a hexagonal phase of CdSe.