Opto-electronic properties of molybdenum doped indium tin oxide nanostructured thin films prepared via sol–gel spin coating

Molybdenum-doped indium tin oxide thin films were synthesized using sol–gel spin coating technique. The influence of different molybdenum-dopant contents on the electrical, optical, structural, and morphological properties of the films were characterized by means of four point probe, UV–Vis–IR spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and atomic force microscopy. For this purpose, addition of different molybdenum contents with tin at a fixed 6 at% is considered as the first approach. For the second and third approaches, different molybdenum-doping contents were added at a constant atomic ratios of In:Sn=94:6 and In:Sn=95:5, respectively. Obtained results indicate that minimum resistivity of 22.3×10−3 Ω cm and optical transmittance of more than 80% in the UV–Vis–IR region with a band gap of 3.83 eV were achieved for the films prepared through the first approach at molybdenum and tin doping contents of 0.5 and 5.5 at%, respectively. X-ray diffraction analysis confirmed the formation of cubic bixbyite structure of indium oxide and rhombohedral structure of indium tin oxide for molybdenum-doped films with small shift in a major peak position to lower diffraction angles with the addition of molybdenum. Field emission scanning electron microscopy micrographs do not show any specific changes in grain size of the films with addition of molybdenum beside tin. Atomic force microscopy studies show that the addition of molybdenum at optimum content to indium tin oxide films results in the formation of films with compact surface and less average roughness than the undoped indium tin oxide films.