Physical properties of copper-treated cadmium telluride thin films by vacuum evaporation technique

Cadmium telluride thin films were prepared on microscopic glass substrates by vacuum evaporation technique. The morphology of the thin films as a function of substrate temperature and postdeposition heat treatment was investigated by atomic force microscopy. The grain size increases with the increase of substrate temperature and postdeposition annealing. Calculated amount of copper was evaporated to deposit on the top of the already deposited CdTe thin films. The whole assembly was then annealed at 450°C for about 4–6 min. These samples were characterized structurally, optically, and electrically by using XRD, spectrophotometer, and Hall Effect measurements, respectively. Doping with Cu has significantly changed the electrical properties of the CdTe films. The measurements have shown band gap of 1.475 eV and resistivity ranging from 0.132 to 0.002 Ω cm, depending on the copper concentration. Increase in the weight percentage of copper showed decreasing trends in resistivity up to 3 wt%. Mobility showed the opposite behavior than those of the resistivity. The carrier concentration showed a systematic increase.