Raman Characterisation of $Cd_{1-x}Zn_x$ Te Thick Polycrystalline Films Obtained by the Close-Spaced Sublimation

In this work, we studied the Raman spectra of thick polycrystalline $Cd_{1-x}Zn_x$ Te (CZT) films with x ranged from 0.06 to 0.68. Additionally, the surface morphology and structural properties were studied in order to determine the crystalline quality of the samples. The Raman spectra had a two-mode behavior typical for CZT solid solution and showed CdTe- and ZnTe-like longitudinal and transverse optical modes. The relationship between the frequencies of CdTe- and ZnTe-related modes on x was studied. We observed the deviation of the compositional dependence of phonon mode frequencies for polycrystalline CZT films in comparison with a similar dependence for CZT single crystals. Such deviation was caused by the effect of structural defects in polycrystalline films on frequencies of vibrational modes. The values of excitation wavelength, which allow achieving of high signal-to-noise ratio on the Raman spectra of CZT films with different zinc concentration in the result of resonant enhancement of phonon modes intensities, were experimentally determined.