Topological insulators (TI) have attracted immense attention due to the unusual conducting surface states discovered in the recent past. Developing high-quality thin films of TI is crucial for the development of planar devices. Thin films of Bi2Te3, a well-known TI material, were grown by RF sputtering at room temperature for different thicknesses ranging from 70 nm to 320 nm. The structural and optical properties show organized growth in the c-axis from a thickness of 70 nm up to 200 nm. At a thickness of 320 nm, the sample exhibits bulk behaviour. The optical energy gap was found to be greater than its bulk value (0.19 eV), which could be attributed to quantum size effects, density of localized states and barrier height differences due to varying crystallite sizes.