Study on the Effects of Precursor Concentration and Annealing Process of In₂O₃ thin Films Prepared by Sol-gel Method

In this paper, In₂O₃ thin films were prepared on quartz glass substrate by sol-gel method using indium nitrate hydrate (In(NO₃)₃·xH₂O) as precursor, ethylene glycol(C₂H₆O₂) as solvent, and acetylacetone(C₅H₈O₂) as catalyst. The effects of precursor In³⁺ concentration, annealing temperature, and annealing time on the properties of In₂O₃ thin films were experimentally investigated. With As the concentration of In³⁺ in the precursor solution increases, the diffraction peak of the (222) crystal plane becomes stronger and sharper, indicating that the preferred orientation of the In₂O₃ film along the (222) crystal plane is becoming stronger and the crystallinity is getting better. The average grain size increases, the lattice strain and dislocation density decrease, the roughness and film thickness increase, and the optical transmittance and optical band gap decrease. With the increase of annealing temperature and annealing time, the diffraction peak intensity of In₂O₃ film increases, the half-high width of the diffraction peak shrinks, the average grain size increases, the light transmittance increases, the crystal defects decrease, the crystal structure is more orderly, and the crystallinity of the film increases. At the same time, the optical band gap remains almost constant.