Air-annealed growth and characterization of Cd1-xZnxTe thin films grown from CdTe/ZnTe/CdTe multi-stacks

CdTe/ZnTe/CdTe thin film layers were vacuum-evaporated on glass-slides and annealed in box-furnace in the air. The samples were annealed at different temperatures of 350°C, 400°C and 450°C, respectively. At each temperature, three sets of samples were annealed for one, two and 3 h, respectively. The films showed good inter-diffusion and high crystallinity even at a lower temperature of 350°C. The 111(C) and 220(C) Cd1-xZnxTe planes showed an increasing left-hand shift in the 2θ axes, along with increasing annealing time and temperature. This trend is attributed to strain relaxation with increased annealing. Cd1-xZnxTe particle-size showed a sigmoid growth along with increasing temperature and time, while strain, dislocation-density, and the number of crystallites per unit area showed a sigmoid decay curve. At lower temperature, samples showed reduced bandgap due to charged defects and impurities like free Tellurium. At higher temperature bandgap increased, because of wire-like formation of TeO2 and their probable substitutional incorporation into Cd1-xZnxTe lattice sites. The TeO2 gradually formed into clusters. EDX results were finally co-related with the optical, structural and morphological results.