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ANNEALING-INDUCEDPHASE CHANGES AND VARIATIONS IN THE OPTICAL PROPERTIES OF CuS AND CuSe THIN FILMS SYNTHESIZED BY THE CBD TECHNIQUE

Bernice Y. Danu, Isaac Nkrumah, Francis K. Ampong, Robert K. Nkum, Francis Boakye


An investigation has been carried out to determine the annealing-induced variation in the optical properties and possible phase changes that may occur in CBD synthesised CuS and CuSe thin films. Analytical techniques such as, Powder X-ray diffraction and optical absorption spectroscopy were used to characterize the films. The composition of the films and their phases were confirmed by Powder X-ray diffraction. Results showed that the as-deposited copper sulphide had several phases and after annealing in air, several copper sulphate phases were detected with copper sulphate pentahydrate being the dominant phase. The optical band gap of copper sulphide was 1.68 eV for the as-deposited sample and changed to 2.20 eV after annealing. Structural analysis of the copper selenide samples showed the presence of several phases in the as-deposited sample. After annealing, the diffraction pattern showed the presence of a single phase, krutaite with preferred orientation along the (111) plane. No diffraction peaks from other species could be detected in the annealed copper selenide sample, which seems to suggest that the obtained sample is pure The as-deposited copper selenide films possessed two band gaps of 1.20 and 1.33 eV which could be attributed to the presence of several phases. After annealing, the band gap changed to 2.20 eV. There was an increase in the average grain size of both the copper sulphide and copper selenide samples after annealing suggesting a further growth in grain size at this temperature.