Influence of compositional variation on the optical and morphological properties of Ge Sb Se films for optoelectronics application

Abstract Thin films of Ge x Sb 40-x Se 60 (x = 15, 20, 25, 27, 32 and 35 at.%) were deposited on quartz by vacuum thermal evaporation of the pre-synthesized parental glasses powders. By spectroscopic ellipsometry the complex refractive index values are determined in the 0.20–33 μm spectral range. The optical band gap and single oscillator energies are established as a function of the Ge content and average coordination number Z . In the (0.85–3.5) μm spectral range the Ge x Sb 40-x Se 60 films possess about 80% transmission. Infrared ellipsometric and Raman studies identified Se Se and Ge Ge homopolar bonds, oxygen and hydrogen related impurity bonds and heteropolar Ge Se and Sb Se chemical bonds. Neutron- and X-ray Diffraction data coupled with Reverse Monte Carlo simulations support the optical results reproducing the Ge Se and Sb Se cell units and cross-linked Ge Ge bonds. Atomic force microscopic imaging confirmed smooth surfaces with low RMS roughness values ( x Sb 40-x Se 60 films.