Effect of Annealing Atmosphere and Temperature on Structural, Optical and Electrical Characteristics of Hydrogenated ITO Films

Indium tin oxide (ITO) films were deposited by RF magnetron sputtering with different H2 flow rates (0, 0.5, and 1 sccm) and subsequently annealed at 200 400 °C under Ar and air atmospheres. The results show that as-deposited ITO films exhibit significant compressive stress, along with a (211) preferred orientation. With increasing annealing temperature, the compressive stress in the films gradually releases, and the crystallite size initially decreases before increasing. Except for the emergence of a (400) preferred orientation in the films prepared with 0.5 sccm H2 after air annealing, the annealing generally results in the weakening or disappearance of the preferred orientation. For films deposited under Ar atmosphere (0 sccm H2), annealing in both Ar and air atmospheres significantly increases the carrier concentration. For films deposited under Ar + H2 atmosphere, the carrier concentration increases after Ar annealing but remains largely unchanged after air annealing. The chemical states of O, In, and Sn in the films were analyzed by XPS, and the changes in carrier concentration were discussed in relation to factors such as increased oxygen vacancy (VO) content, activation of Sn doping, and outdiffusion of hydrogen. The critical carrier concentration that determines crystallite boundary or ionized impurity scattering mechanism was identified through the relationship between mobility and carrier concentration. The optical transparency of the films first increases and then decreases with rising annealing temperature. With the change of annealing conditions, the trend of energy gap (Eg) and carrier concentration is consistent, confirming the Burstein-Moss (BM) effect.