The effect of thickness on the structural and optical properties of nano Ge-Te-Cu films

Quartz was used as a substrate to hold different film thicknesses of Ge0.15Te0.78Cu0.07 within range 100-500 nm prepared by thermal evaporation technique. Films are still amorphous up to 200 nm and turn to more ordered nano polycrystalline one by ascending the values of film thickness up to 500 nm. Films turn to crystalline phase due to annealing. The relation of resistance and temperature shows phase transformation. Optical constants; refractive index, n absorption coefficient, alpha single-oscillator energy, E-o dispersion energy, E-d lattice dielectric constant, epsilon(L) infinite wavelength dielectric constant, epsilon(infinity) the ratio of the carrier concentration to the effective mass, N/m* optical conductivity, sigma and energy loss function, ELF show decreasing values with thickness up to 200 nm followed by ascending values within range 200-500 nm. It is concluded that the thickness range 100-200 nm introduces more disordered films while 200-500 nm introduces more ordered one.