Effect of Substrate Temperature on the Structural and Optical Properties of CdTe Films Prepared by Thermal Evaporation

Abstract

CdTe thin films are prepared on corning 1,737 glass using simple thermal evaporation technique at three different substrate temperatures, viz., room temperature, 100 and 200 °C. The dependence of the structural and optical properties of the prepared films on the substrate temperature at the time of deposition is studied using X-ray diffraction, UV–Vis–NIR spectroscopy and Raman spectroscopy. The prepared films at higher substrate temperature are having larger grain size and also improved crystallinity. Small changes in the optical band gap and the refractive index are observed. The films prepared at 200 °C have the lowest energy band gap of about 1.45 eV and also highest refractive index. Three phonon modes, i.e., Te–Te A1, LO and TO modes are observed in all the samples. The phonon band centers of the observed modes are slightly blue shifted with increase in substrate temperature. Observed significant broadening in the phonon modes in comparison to the bulk values could be due to the confinement effect in nanocrystals. The surface morphology of the films is studied using field emission scanning electron microscope.