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Transparent conducting oxide (TCO) thin films, particularly sputter-deposited Sn-doped In2O3 (ITO) have a wide application in optical coatings and optoelectronics. However, due to the scarcity and increasing cost of indium, efforts have been done to search for indium-free materials. Sputter-deposited Nb-doped TiO2 (NTO) is among recent materials which have shown great potential for TCO applications. In this study we report and discuss on the influence of films’ thickness on the optical properties of Nb-doped TiO2 (NTO) films deposited on glass substrate from an alloy target of Ti0.99 Nb0.01 (purity 99.9%). It was observed that luminous transmittance (Tlum), solar transmittance (Tsol) and the band gap energy (Eg) increased with increased films thickness while optical constant (n,k) decreased with films thickness. An average Tlum and Tsol of above 60% and a relative increase of IR reflectance were achieved. The results implied a possibility for achieving lowemissivity (low-E) material upon improving the IR reflectance by raising the Nb-doping level.
The author acknowledges the Belgian Technical Cooperation (BTC) for the scholarship and Material Science and Solar Energy Network for Eastern and Southern Africa (MSSEESA) for facilitating travel to Nairobi and Moi University in Kenya for optical characterization.