Studies on cadmium telluride–cadmium selenide bilayer

Abstract

Group II–VI elements of the periodic table are suitable for electronic and optoelectronic applications. Cadmium selenide (CdSe) and cadmium telluride (CdTe) bilayer films were deposited onto well-cleaned glass substrates using vacuum evaporation technique. These films were analyzed using X-ray diffraction, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDAX) and UV-visible spectrophotometry to study their microstructural, morphological and optical properties. Crystallinity of CdSe film increased with increase in film thickness, which in turn favored the crystallinity of the CdTe layer deposited over CdSe. The CdTe/CdSe bilayer showed globular surface morphology, and the grain size of the films measured by FE-SEM micrographs range from 16 to 31 nm. EDAX analysis confirmed the presence of cadmium (Cd), selenium (Se) and tellurium (Te). Two electronic transitions were observed in the optical band gap of the CdTe/CdSe bilayer whose energy levels lie in between the energy band gap of the bulk CdTe and CdSe semiconductors. These electronic transitions are mainly due to the spin orbit split of valence band energy levels.