Microstructure and optical properties of zinc nitride films deposited by magnetron sputtering method

Zinc nitride films were coated on a glass substrate by reactive magnetron sputtering method using a zinc target and a mixture of N2 and Ar gasses. The deposited films were characterized for microstructure, surface morphology and optical properties. These films possess a polycrystalline structure and a high electrical conductivity. The optical properties indicate that the films have high transmittance in the infra-red (IR) region with a very sharp optical absorption edge in the IR range corresponding to the band gap of zinc nitride. The band gap energy of deposited films was estimated to be 1.2 eV, which slightly decreased when the films were annealed at 300 °C. This effect is interpreted as due to release of extra nitrogen from the films during annealing. The electrical conductivity of the as-deposited films is 5 × 102 Ω·cm, and it decreases by annealing of these films in the air or O2. The zinc nitride films annealed in the air or O2 exhibited some photoconductivity; however, no photoconductivity was observed for the as-deposited films.