Microstructure, Chemical Composition And Photoelectrical Properties Of ITO Transparent Conductive Films

Indium-tin-oxide (ITO) films are prepared by direct current (DC) magnetron sputtering. The target is In₂O₃: SnO₂ (90:10wt.%, 99.99% purity) ceramic. After deposition, the films are annealed in air at 300℃ for different times (0.5～3.0h) and for 1.0h at different temperatures (100～400℃). The microstructure, chemical composition and photoelectric properties of the films are analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Ultraviolet-Visible Spectrophotometer and four-point probe instrument. Microstructure analysis shows that the films still keep the bixbyite crystal structure as In₂O₃. No existence of Sn or Sn oxide diffraction peaks suggests that Sn has been introduced into In₂O₃ lattice, forming polycrystalline ITO. TEM analysis indicates that when annealed at 300℃, ITO average granularity increases with increasing annealing time. XPS analysis shows that when annealed at 300℃, with increasing annealing time, Sn⁴⁺ concentration in the films increases to 88.6at.% and then keeps constant. When annealed for 1h, with increasing annealing temperature, 1) Sn⁴⁺ concentration in the films increases, and 2) In³⁺ concentration decreases and then increases, indicating the oxygen vacancy content in the ITO films increases and then decreases. The photoelectrical property analysis shows that after annealing the ITO films represent excellent transparent and conductive performance: the average transmittance over 390⁷60nm enhances, energy gap broadens, electrical resistance decreases an order, and figure of merit increases to 9.88×10^-3Ω^-1.This paper consists of four chapters. The first one is an introduction, summarizing the background, significance and related researches. The second one represents the theoretical foundation and practical application of ITO films. The third chapter expatiates on the film preparation and the influence of annealing condition on film microstructure, chemical composition and photoelectrical properties. The fourth one is conclusion.