Influence of sputtering power on structural, optical and electrical properties of CdTe thin films prepared by DC magnetron sputtering

Abstract

The cadmium telluride (CdTe) thin films have been successfully deposited on glass substrates by direct-current (DC) magnetron sputtering method, and the structural, optical and electrical properties of samples were investigated in this paper. X-ray diffraction patterns revealed that all samples exhibited a preferred orientation along (111) plane with cubic phase, and the crystallite size was first increased from 13.6 to 42 nm and then decreased to 31 nm as the sputtering power increased from 10 to 80 W. AFM images showed that surface morphology of CdTe films was affected by the sputtering power and the particles in the films exhibited uniform distribution with obvious RMS roughness (25.9 nm) as the sputtering power was 40 W. Meanwhile, CdTe films appeared a higher transmission properties in the range of 850–1000 nm, and the band gap of films gradually decreased from 1.96 to 1.51 eV and then increased to 1.67 eV as the sputtering power constantly increased. Raman spectrum revealed that the peak at 140 cm−1 exhibited dominant among other peaks, associated to the E mode of Te. The current–voltage (I–V) curves indicated that the conductivity of CdTe films was strongly dependent on the sputtering power and the optimal electrical properties could be achieved at the sputtering power of 40 W.