STRUCTURAL, ELECTRICAL AND OPTICAL-PROPERTIES OF SOLUTION GROWN POLYCRYSTALLINE CU1-XAGXSE THIN-FILMS

Polycrystalline thin films of Cu1-xAgxSe (0 less-than-or-equal-to x less-than-or-equal-to 1) have been deposited by a 'solution growth' technique. As-deposited films have been annealed at different temperatures up to 500 K and the appearance of electrical conductivity has been observed. The electrical conductivity of annealed films shows an exponential dependence on temperature, and two thermal activation energies have been calculated. Excluding x = 0, all the films displayed n-type conductivity. Carrier concentration, mobility and thermoelectric power measurements of these films have been carried out as a function of composition. X-ray analysis indicates that CuSe and AgSe films have a cubic crystal structure while films with 0.1 less-than-or-equal-to x less-than-or-equal-to 0.9 possess a tetragonal structure with axial ratio approximately 1.25. Films of stoichiometry 0.1 less-than-or-equal-to x less-than-or-equal-to 1 show both a direct and an indirect optical bandgap E(g) from 1.4 to 1.37 eV and from 1.19 to 0.99 eV respectively. Other parameters such as absorption coefficient-alpha, refractive index n, dielectric constant-epsilon, and extinction coefficient k have also been computed from reflectance and transmittance spectra.