Influence of annealing temperatures on the structural, optical and electrical properties of SnSe films

Crystalline SnSe was synthesized by solvothermal method based on reacting tin chloride with selenium in the presence of ethylenediamine. SnSe thin films were grown on glass and quartz substrates by using thermal evaporation technique. The films were annealed at 150 and 300 °C. The influence of annealing temperatures on structural, morphological, optical and electrical properties of SnSe thin films has been investigated. The results showed that the as-deposited SnSe thin films have orthorhombic structure. Upon annealing at 150 °C, the crystallinity of the films increased. By annealing at 300 °C, the films are partially transformed to SnSe₂ with hexagonal structure. The absorption coefficient and refractive index were calculated and analyzed. It is found that the as-deposited and annealed films have direct and indirect transitions with optical band gap increases with increasing annealing temperature. The optical dielectric constant and the ratio of the free carriers concentration to its effective mass were calculated for as-deposited and annealed films. From electrical measurements, the films showed semiconductor behavior. The resistivity, carriers concentration and carriers mobility are studied as a function of heating temperature and annealing temperature.