Effect of precursor concentration on the properties of ITO thin films

Tin-doped indium oxide (ITO) thin films have been prepared by the spray pyrolysis method using indium chloride as a precursor and stannic chloride as a dopant. The effect of a precursor concentration on the structural, morphological, electrical and optical properties of films has been studied. The concentration of InCl3 in the spraying solution is varied from 6.25 to 37.5 mM keeping doping percentage of tin fixed at its optimized value of 5 wt.%. Bare glass is used as a substrate and oxygen as the carrier and reaction gas. X-ray diffraction (XRD) patterns show that films are polycrystalline and their crystallinities are dependent on the precursor concentration. A surface morphology has been observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The typical ITO film has minimum resistivity value of 2.71 × 10−3 Ω cm, whose carrier concentration and mobility were 7.45 × 1019 cm−3 and 31 cm2/(V s), respectively. In addition, the best ITO film has optical transmittance of 94.4% and figure of merit 1.20 × 10−3 Ω−1.