Influence of RF power on the opto-electrical and structural properties of gallium-doped zinc oxide thin films

Abstract

GZO thin films were succesfully deposited onto n-Si and glass substrates by RF magnetron sputtering at room temperature. The structural, morphological and opto-electrical properties of the films were investigated in terms of RF power, using various methods such as XRD, AFM, SEM, EDX, XPS, SIMS, UV-Vis-NIR spectroscopy and Hall effect measurements. The achieved results revealed that the all films have highly c-axis (002) oriented polycrystalline structure with high transmittance in Vis and high reflectance in NIR region as well as good conductivity. Meanwhile, surface of the films was uniform, compact and crack-free. With incerasing of RF power, it was seen that crystallinity of the films improved and the grain size became larger. It was also observed that optical band gap of the films was increased to the order of 0.15 eV as well as decreasing the resistivity to the order of 6.38 Omega cm with increasing RF power from 100 to 200 W. Deposited film at 200 W, which can be optimum sputtering power for coating GZO films, having high concentration of free electrons and lowest resistivity exhibited the highest IR reflectivity (55%) in NIR region. In addition, deposited GZO films at this power have larger particle size and highly optical transmittance (87%) in visible region. Obtained both of optical and electrical results suggested that the deposited GZO films can be used in low thermal emissivity coating for energy efficient glass and the UV-blocking layer as well as transparent conductive oxide electrode for flexible opto-electronic devices.