ITO Films Deposited on Silicon by CVD Method

Indium tin oxide (ITO) films on polycrystalline p-silicon substrates were obtained by an improved chemical vapor deposition method in a quasi-closed volume at the normal atmospheric pressure by thermal decomposition of vapors of alcoholic solutions of indium chloride and tin chloride. In order to clarify the dependence of the properties of ITO films on the substrate temperature and the ratio X = SnO₂/In₂O₃, the layers were synthesized in the temperature range 170–500°С in various X ratios solutions of indium and tin chlorides. The technological modes of the synthesis were set by controlling the temperature of the substrate and evaporators, to which alcoholic solutions of indium and tin chlorides were supplied, as well as by changing the ratio of the components and the rate of supply of the solution. Under such synthesis conditions, the film growth rate was ∼0.5–1.0 µm/h, which is much higher than in the case of spray pyrolysis under similar conditions. The thicknesses of ITO films were determined by using an MII-4 interference microscope and the transmission spectrum; the film thicknesses amounted to ∼3 μm. The dependence of the resistivity of ITO films on the substrate temperature has been studied. It was shown that the films obtained at the substrate temperatures of 240–260°C had a relatively low resistivity, so the films are of interest for solar cells applications. The X-ray spectra of ITO films were analyzed by identification with the map 00-006-0416 (In₂O₃, cubic) from the Joint Committee on Powder Diffraction Standard database. The average value of the lattice constant was calculated, and it was a = 10.1273 Å, thus being slightly larger than the lattice parameter of pure In₂O₃ (10.1195 Å), which is associated with the presence of Sn that affects the behavior of oxygen ions.