Preparation Of TiO₂ Thin Films By DC Magnetron Reaction Sputtering And Study On Oxygen-Sensing Properties

There are three crystalline phases of TiO₂ , including rutile, anatase and brookite .Transformation of crystalline phases occurs at a certain temperature and pressure. TiO2 thin film is a kind of very important optical film which has high transmission rate and refraction rate in visible light area. TiO₂ can serve as many kinds of sensors. It can be used as not only humidity and pressure sensing sensors, but also identifying many kinds of gases, mostly oxygen.This paper studys on TiO₂ oxygen-sensing thin films which are deposited by DC magnetron reaction sputtering. TiO₂ thin films are prepared under the condition of background vacuum 2.4x10-3Pa, sputtering voltage 420V, sputtering current 0.3A, oxygen partial pressure 0.17Pa and sputtering total gas pressure 1.5Pa. The crystal structure is amorphism when TiO₂ thin films are not annealed; anatase.when annealed at 300℃; coexistence of anatase and rutile when annealed at 600℃; completely rutile when annealed at 1000℃. For the sample annealed at 1000℃ , sensitivity increases with growth of oxygen partial pressure at a constant temperature. The higher is the working temperature, the slower is the sensitivity increasing. Sensitivity increasing with oxygen partial pressure is the fastest and average sensitivity is the highest at 200℃. When oxygen partial pressure ratio is 0.405, 0.576 and 0.692, the activation energy is respectively 0.391eV, 0.449eV and 0.498eV by calculation. The results of activation energy are lower, which illuminates that the temperature stability of the TiC>2 oxygen-sensing thin film is improved to a certain extent. The conductive influence factor of the oxygen-sensing thin film is morecomplicated. Ti_int³⁺,Ti_int⁴⁺ and V_O²⁺ coexist and all play a role in the formation of conductionmechanism; operation of Ti_int³⁺ is the most significant.The oxygen-sensing properties of the samples are better under the preparation condition of the lower po₂/p_Ar and the more oxygen partial pressure. The samples annealed at 1000℃ aremore sensitive to oxygen than those annealed at 600℃. We consider that the higher annealing temperature can facilitate the formation of rutile TiO2 which has the most perfect oxygen sensing properties in the three crystalline phases of TiO2.