Effect of annealing temperature on the structure and optical properties of sputtered TiO2 films

Abstract

TiO2 thin films were deposited by DC reactive magnetron sputtering. Some TiO2 thin films samples were annealed for 5min at different temperatures from 300 to 900°C. The structure and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and ultraviolet–visible (UV–vis) spectrophotometry, respectively. The influence of the annealing temperature on the structure and optical properties of the films was investigated. The results show that the as-deposited TiO2 thin films are mixtures of anatase and rutile phases, and possess the column-like crystallite texture. With the annealing temperature increasing, the refractive index and extinction coefficient increase. When the annealing temperature is lower than 900°C, the anatase phase is the dominant crystalline phase; the weight fraction of the rutile phase does not increase significantly during annealing process. As the annealing temperature rises to 900°C, the rutile phase with the large extinction coefficient becomes the dominant crystalline phase, and the columnar structure disappears. The films annealed at 300°C have the best optical properties for the antireflection coatings, whose refractive index and extinction coefficient are 2.42 and 8×10−4 (at 550nm), respectively.