Effect of Annealing Treatment on the Properties of Stoichiometric Indium Zinc Tin Oxide (IZTO) Thin Films

Indium zinc tin oxide (IZTO) thin films were deposited onto glass substrate by RF magnetron sputtering method. IZTO ceramic targets with four different chemical compositions corresponding to In_{1 –2 x} Zn _x Sn _x O_1.5 (x = 0.20–0.35), i.e., IZTO20, IZTO25, IZTO30, and IZTO35, were employed as the sputtering sources. The deposition was carried out in pure argon atmosphere at 400 °C. As-deposited IZTO films were then annealed at varying temperatures for 30 minutes under argon or reducing gas (Ar + H₂) atmosphere in order to further reduce the resistivity value of the films. The structural, optical, and electrical properties of the films were examined by X-Ray diffraction (XRD), UV-Vis spectrometry, and Hall effect measurement. The resistivity of IZTO films with decreasing indium content down to 40 at.%, i.e., IZTO30 film was successfully reduced to 5 × 10^–4 Ω · cm after annealing treatment at 450 °C. Even lower resistivity value of 3 × 10^–4 Ω · cm was obtained from one of the non-stoichiometric compositions in IZTO system. The work function value increased accordingly with the reduction of indium content as the film became more amorphous than the films with higher indium content, indicating the fact that IZTO films with low indium content might be suitable for organic photovoltaic applications.