Effect of sol-layers on Sb-doped SnO₂ thin films as solution-based transparent conductive oxides

We synthesized dense Sb-doped SnO₂ (ATO) thin films coated with the optimum number of sol-layers to form solution-based tranparent conductive oxides (TCOs) using a hydrothermal method and spin-coating. To investigate the effects of the sol-layers on the ATO thin films, samples with 0, 1, 3, 5, and 7 sol-layers were deposited on ATO thin films with porous surface morphologies. The structures, chemical states, morphology changes, and electrical and optical properties of the samples were demonstrated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Hall effect measurement, and UV-vis spectrophotometry. In particular, ATO thin films coated with 5 sol-layers exhibit superb resistivity, good transmittance, and a superb figure of merit (FOM) compared to the other samples. The performance enhancement could be explained in two ways; (1) densification and thickness increase by sol coating and finally, (2) the dominant increase of the carrier concentration with small decrease of the electron mobility.