Tabitha A. Amollo, Qi Hua Fan, Michigan State University, East Lansing, MI
Currently, indium tin oxide (ITO) is the commonly used transparent electrode material in optoelectronic devices. Because of cost and scarcity of indium, the main component of ITO, alternative transparent conductive oxides (TCOs) are needed. Besides, given the expanding market of transparent conductive electrode applications, alternative TCOs are inevitable for sustainability. In this study, tantalum doped tin oxide (TTO) is studied, showing promising electric and optical properties as an alternative to ITO. Two critical factors contribute to the attractive properties of TTO thin films. 1) Tantalum has an ionic radius nearly matching that of tin thus is easily incorporated in tin oxide lattice at low formation energy, and without production of secondary phase or strains. 2) TTO thin films are deposited using a unique single beam ion source enhanced magnetron sputtering, which enables effective modulation of the film structures even at low temperatures below 200 ֯C. This work reports the effects of substrate temperature and deposition angle on the film structure and properties. The thin film’s microstructure is analyzed using x-ray diffraction while the morphology is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Electrical conductivity and optical transmittance of the thin films are determined from four-point probe and UV-Vis spectroscopy measurements, respectively. On the other hand, Hall effect measurements are carried out to determine the charge carrier concentration and mobility. Development of alternative TCOs will ensure sustainability in the production of transparent electrode devices.