Investigations on Properties of (ZnO:Al) Films Prepared by RF/DC Co-sputtering

Aluminum doped zinc oxide (ZnO:Al) thin films with high conductivity, resistance to ion irradiation, high transparency in the visible range and moderate costs will be one of the most promising candidates for the present predominant transparent conducting materials. However, there are still some problems such as long preparation cycle and high surface resistance. In this paper, adding a certain amount of radio frequency (RF) power to the applied DC power, this technique known as RF-DC co-sputtering ionization is mainly driven by oscillating electrons in the bulk plasma, there is an enhanced substrate bombardment by plasma ions (mainly Ar+) of moderate energy to improve the optical and electrical properties of the film. Such a moderate energy ion bombardment can assist the film growth and lead to better and denser films. By variation of the RF/DC power ratio, we prepared at a relatively higher sputter rates and higher discharge voltage. The samples of crystal structure, surface morphology, electrical conductivity were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), four-probe meter, as well as visible spectrophotometer. The results show that the average transmittance in the visible was 89% and the resistivity was reduced by 80% compared to other single technique. When the radio frequency power makes up around 50% of the total, the resistivity reach a minimum of 1.5×10-3Ω•cm, improve the homogeneity of the film Effectively.