(400)-Oriented indium tin oxide thin films with high mobility and figure of merit prepared by radio frequency magnetron sputtering

Abstract

In this paper we report synthesis of highly conducting and optically transparent indium tin oxide (ITO) films with high charge carrier mobility using radio frequency (RF) magnetron sputtering without any post-annealing treatment. All deposited films show high optical transmittance in the visible region (> 85%) and the band gap ~ 3.54 eV. Based on the x-ray diffraction, atomic force microscopy, scanning electron microscopy and Hall measurement analysis the influence of RF power on ITO crystal growth mechanism have been discussed. It has been observed that with increasing RF power the preferred crystal orientation in films changes from (222) to (400) direction. A significant increase in charge carrier mobility have been observed with change in crystal orientation from ~ 45 cm2 V−1 s−1 in (222) direction to ~ 380 cm2 V−1 s−1 in (400) direction. At optimized RF power (90 W), ITO film with maximum figure of merit (φTC = 150×10−3 Ω−1) with high optical transparency (~ 94%) and high conductivity (2.8 × 103 Ω−1cm−1) have been obtained. We believe that employment of such high mobility and high figure of merit ITO films can have potential applications in various opto-electronic devices such as smart windows, gas sensors, solar cells, light spreading electrode in light emitting diodes and organic light emitting diode displays.