Mo-doped indium oxide films by dip-coating: synthesis, microstructure and optical properties

Molybdenum doped indium oxide (In2−xMoxO3, IMO) is widely used in many electronic and optoelectronic devices due to its excellent electrical properties and optical transparency. In this work, a first attempt to produce IMO films by sol–gel dip coating was reported, starting from different reagents (i.e. indium nitrate or indium chloride and molybdenum chloride or ammonium molybdate as In and Mo sources, respectively). The influence of different reagents, solvents and annealing atmospheres (i.e. air and N2) on final coating properties was investigated in order to properly select the optimal process parameters. The morphological, microstructural and optical properties of the produced coatings were evaluated by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and UV–vis spectroscopy. The best performances, in terms of microstructure and transparency, were obtained for films produced by dip coating the indium nitrate and molybdenum chloride based solutions (In nitrate concentration 0.1–0.2 M), with the addition of a low amount of PEG, followed by annealing at 500 °C. The produced coatings consisted of monophasic In2O3 and were characterised by a uniform, homogeneous and cracks free surface, and high transmittance values in the vis range (i.e. 85–98%).