Structural, optoelectrical, linear, and nonlinear optical characterizations of the Cu2ZnGeSe4 thin films

Abstract

Good quality copper zinc germanium selenide (Cu2ZnGeSe4) thin films were grown via thermal evaporation procedure with different thicknesses (261, 379, and 486 nm). The analysis of the X-ray diffraction examination of the Cu2ZnGeSe4 thin films demonstrates that the as-deposited Cu2ZnGeSe4 thin films are polycrystalline with a single-phase tetragonal structure. The elemental composition analysis of the evaporated Cu2ZnGeSe4 thin film established that the as-deposited film is near stoichiometric in the compound. The optical study on the Cu2ZnGeSe4 thin films displayed that the Cu2ZnGeSe4 films exhibited a direct allowed optical transition and by increasing the thickness the magnitudes of the direct bandgap were decreased from 1.47 to 1.31 eV while the Urbach energy increased. The effect of thickness on the skin depth δ, absorption coefficient , linear refractive index n, and the static refractive index no of the Cu2ZnGeSe4 thin films was studied. The analysis of the nonlinear optical parameters of the Cu2ZnGeSe4 thin films reveals the increase of the film thickness combined with increase in the nonlinear refractive index.