Implications of Changing the Cd-Ge-Se Thin Film Thickness Deposited by Thermal Evaporation Technique on Structural and Optical Properties for Optoelectronic Applications

The present research article examined how the thickness of Cd2Ge8Se90 thin films affected their structural and optical characteristics. On pre-cleaned glass substrates, the pristine amorphous Cd2Ge8Se90 thin films of varying thicknesses (d=374, 516, and 816 nm) were synthesized.Swanepoel's strategy was employed to explore the optical characteristics in terms of film thickness, such as the band gap energy (Tauc’s energy) and band tail energy (Urbach’s energy). Also, optical constants, including the refractive index, n, and extinction coefficient (absorption index, k), depend on transmittance spectroscopy.An indirect optical transition mechanism is observable, according to the assessment of the absorption spectra of the thin films under study.As layer thickness increased, the optical band gap shrank, but the tail energy showed a different pattern of this behavior.The refractive index dispersion was characterized using the Wemple-DiDomenico single oscillator concept, and the dispersion parameters were derived.Oscillator and dispersion energies rise as a film's thickness does. Other dielectric parameters including the high-frequency constant, the ratio of free charge carrier concentration to effective mass, plasma frequency, and single oscillator strength are all significantly influenced by thickness.