Annealing Effects on Electrical Properties of Pure and Tin-Doped Indium Oxide Thin Films

摘要

The annealing effects on the properties of ITO and pure In_2O_3 thin films have been investigated. The thin films were deposited with various O_2 flow ratios to total gas flow by pulsed dc magnetron sputtering. The post-deposition annealing of the thin films was carried out for 30 minutes at various temperatures ranging up to 500℃ in air. It was found through the comparison of the carrier density of ITO and In_2O_3 thin films that the carrier electrons of the ITO thin films came from both of the dopant Sn and oxygen vacancies under the annealing less than 400℃. Therefore, the ITO thin films deposited with lower O_2 flow ratio exhibited higher carrier density due to many oxygen vacancies; in consequence, they exhibited lower resistivity at the annealing up to 400℃. On the other hand, the carrier density of ITO thin films was almost identical regardless of O_2 flow ratio when they were annealed at 500℃. This fact indicates that most carrier electrons of the ITO thin films were brought by the dopant Sn at the annealing temperature of 500℃. However, the ITO thin films deposited with lower O_2 flow ratio exhibited higher Hall mobility; as a result, they showed lower resistivity at the annealing of 500℃. Atomic force microscope, X-ray diffraction and X-ray reflectivity measurements revealed that the ITO thin films deposited with lowe O_2 flow ratio exhibited dense structure even after they were annealed at 500℃. Hence, the carrier electrons of the dense ITO thin films deposited with low O_2 flow ratio can conduct better, as a result, the ITO thin films exhibited high Hall mobility and low resistivity.