Controlling opto-electric properties of cadmium stannate thin films deposited by RF sputtering
Date
2011
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Publisher
University of Delaware
Abstract
In this research, the optical and electrical properties of cadmium stannate thin films were studied in order to determine how these properties depend on the deposition and heat treatment conditions used during film formation. Trends in band gap energy, transmittance, mobility, resistivity and carrier density were studied, as well as the growth rate and the indices of refraction and extinction. Optical data was primarily measured using variable angle spectroscopic ellipsometry. In the process of acquiring this data, a procedure for accurately determining the optical properties using variable angle spectroscopic ellipsometry was developed. Ultimately, samples achieved the highest quality when deposited in 5% atmospheric oxygen at room temperature and heat treated at 600 ºC in contact with a cadmium sulfide layer in an argon atmosphere. It was found that oxygen content and film thickness may affect the heat treatment process, while temperature treatments below 600 ºC will not sufficiently induce crystallization. Further study should be given to controlling the cadmium sulfide diffusion rate in order to optimize carrier density and mobility.