Transparent conducting oxides (TCOs) consisting of semiconducting oxides viz tin, indium, zinc, and cadmium, and metals such as silver, gold, and titanium nitride have been known and employed technologically for more than 50 years, primarily in the form of doped single-cation oxides like indium and tin. When doped with appropriate dopants these oxide films shows superior electrical and optical performance and can be widely used in the varieties of fields of science and technology. Now a days they are utilized in number of applications viz. flat-screen high-definition televisions, high-resolution screens on portable computers, electrochromic windows, hand-held new smart displays, optoelectronics, flat panel displays (FPD), solar cells, gas sensors, photo-catalysts, photoelectric-catalysis and so on. The properties of a TCO layer are found to depend on its chemical composition as well as the method used for its preparation. The quality of the thin films is judged in terms of figure of merit for which high transparency and low sheet resistance are the vital parameters.