The ZnO and Mo:ZnO thin films were deposited by radio frequency magnetron sputtering on quartz and intrinsic silicon (100) substrates at a fixed combined partial pressure ？mbar of Ar + O2 and substrate temperatures of 473？K and 673？K. The effect of Molybdenum doping on ZnO thin films with different Molybdenum concentrations (1-2 atomic percent) was studied with the help of structural and microstructural characterization techniques. The films deposited at a substrate temperature of 473？K exhibited strong c-axis orientation with predominant (002) peak. At 673？K, along with (002) orientation, other orientations (100), (101), (220), and (103) were also observed. Among these, the (220) peak indicates the cubic phase of ZnO. With increasing Molybdenum concentration, the cubic phase of ZnO disappeared, and the (002) orientation became strong and intense. The composition analysis reveals that the undoped ZnO films deposited at 473？K have oxygen deficiency, and the ratio of Zn/O is improved with increasing Mo atomic percent in ZnO. The surface morphological features reveal that the undoped ZnO films were found to be uniform and have grain size of around 30？nm. The optical energy gap of the undoped ZnO films is 3.05？eV and increases with increasing Mo concentration. The thickness of the films is around 456？nm. 1. Introduction For the past few years, there has been a lot of interest shown to find new oxide materials which will act as transparent as well as conducting materials. Many metal oxides and their compounds have been found to be transparent and conductve. Among these oxides indium tin oxide (ITO) and aluminum doped zinc oxide (AZO) were proved to be transparent and conducting materials [1–3]. Still there has been a lot of interest shown to overcome the problem involved with those materials like abundance of material, stability, performance, reliability, and durability. So the search for new transparent and conducting oxides continues in the years to come. Various metallic elements doped to ZnO were tested for their transparency in the wavelength range from 450？nm to 750？nm for conductivity. The principal elements doped to ZnO were Al, In, Sn, Ga, Cd [4], and Mo. Among these, an extensive work was done on Al doped ZnO films, and they were proved as potential transparent conductors. Among these, Molybdenum doped ZnO was also found to be an attractive candidate as transparent conducting oxide (TCO) due to its ease to doping to ZnO. Moreover, the difference between the valence electrons of Mo6+ and Zn2+ is 4. This difference can produce enough free carriers
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