Effect of sputtering power on structure and properties of ZTO films

Abstract

Transparent conductive tin-doped zinc oxide (ZTO) thin films were deposited on glass substrate by using radio frequency (RF) magnetron sputtering method. The effect of sputtering power on crystalline structure, morphology, optical and electrical properties of the ZTO film was systematically studied. XRD results showed that the as-deposited ZTO thin films had a hexagonal wurtzite structure, with (002) orientation. Combining with SEM images, it was found that the grain size was increased with increasing sputtering power. The AFM images revealed that low sputtering powers of<210 W should be used to have ZTO films with small roughness (Rq). The optimized sample exhibited an average transmittance of 93.4% in the wavelength range of 400–900 nm, while the band gap had a significant red shift relative to that of the intrinsic ZnO. Carrier concentration and mobility of the ZTO films were decreased, whereas the resistivity was increased, with increasing sputtering power. The sample sputtered at 120 W had the maximized figure of merit (ФTC) of 11.87 × 10−4 Ω−1·sq, with the variation trend to nearly mirror-symmetrical with that of surface roughness of the films.