Tunable optical and electrical properties of sputtered tin-doped indium oxide thin films grown in oxygen free atomsphere

Abstract

Tin-doped indium oxide (commonly named as ITO) is a well-known material vastly used due to its unique behavior of high transparency with electrically low resistive properties. Sputtering is the most common technique due to its large scale, uniform, controllable thin film fabrication approach. To grow high quality sputtered ITO thin films, parameters such as sputtering pressure, power, substrate temperature and dopant concentration plays a key role for its application as transparent electrodes [1-5]. In this work, we have demonstrated the holistic control of optical and electrical properties of sputtered ITO thin films deposited on glass substrates under different process conditions of sputtering pressure, power, and substrate temperature in oxygen free atmosphere. The indium–tin alloy sputter target is used with fixed weight proportion (In2O3:SnO2::9:1). To achieve the process optimization window and to understand the correlation with sputtered ITO films, we have used various characterization techniques including XRD to understand structural behavior, UV-vis spectroscopy for the transmittance as well as reflectance behavior and room temperature Hall measurement to obtain key electrical parameters of resistivity, mobility and carrier concentration. The optimized condition for highly transparent and conductive ITO films on glass substrate is observed with RF power ~ 200 W, working pressure ~ 3.5 mTorr and at the substrate temperature of 400 °C. The corresponding optimum values are; transmittance ~ 97% (in visible region), sheet resistance ~ 10.6 Ω/□, resistivity ~ 1.62 × 10-4 Ω.cm, mobility ~ 39.5 cm2/V-s, carrier concentration ~ 9.77 × 1020 cm-3. These performance characteristics of sputtered ITO films can be used for transparent electrode in various device applications.