The effect of annealing temperature on the properties of CdSe thin films prepared by annealing the SES deposited precursors

Cadmium selenide (CdSe) thin films were grown on quartz glass substrates by thermal annealing of thin-film precursors deposited by successive sputtering, evaporation and sputtering (SES) method. The crystal structure, surface morphology, composition, optical and electrical properties of CdSe films were investigated. XRD analysis revealed that the SES deposited precursors after annealing, were converted into hexagonal CdSe films with a preferential orientation. FE-SEM results showed that the CdSe films obtained at 400 °C and 500 °C were dense, uniform and had greater grains than that obtained at 300 °C, while pores and peeling of CdSe film appeared at 600 °C. EDS results showed that all CdSe films were Cd-rich, and the composition of the CdSe film prepared at 500 °C was closest to the ideal stoichiometric ratio. The formation of CdSe films included atomic diffusions, the selenization reaction and CdSe grain growth, accompanied by volatilization of Cd and Se. The CdSe films exhibited good transmittance of about 60–85 % and band gaps of 1.57–1.67 eV. The PL spectra showed that the CdSe films prepared at different temperatures had a strong emission peak at 782 nm and a weak emission peak at 829 nm, which were possibly caused by the band-to-band transitions and defect emissions. In addition, electrical measurements showed that the CdSe films were n-type conductivity, the resistivity was in the range of 9.65 × 10²-7.55 × 10³ Ω cm, and the carrier concentration was in the range of 5.72 × 10¹⁴-2.99 × 10¹⁵ cm⁻³.