Original research articleThe effect of annealing on the structural, electrical, optical and electrochromic properties of indium-tin-oxide films deposited by RF magnetron sputtering technique

Indium-tin-oxide (ITO) thin films with 200 nm thicknesses were deposited on high temperature glass substrates by RF magnetron sputtering at 200 °C substrate temperature. The effect of annealing temperature on physical properties of the ITO films including crystalline, sheet resistance, optical transparency and electrochromic behavior was investigated. The identification of intrinsic changes in the ITO film properties is crucially important because the ITO films need further treatment by thermal annealing for a wide range of applications. These treatments could alter the initially optimized film properties. By annealing, a red-shift occurred in the optical transmittance of the ITO films. A decrease in the free electron charge density caused by the growth of ITO crystal grains resulted from narrow band gap energies in the range of 3.94 eV-4.05 eV. That is attributed to the decrease of the free electron charge density. The ITO film was annealed at 300 °C in ambient conditions showed a cubic structure (space group: I a-3) and had the optical transmittance of 90% in the visible range. The results indicated that the electrical conductivity of the ITO films was more greatly influenced by the decrease of the electrically active tin dopant concentration in the film structure.