The Study On The Preparation, Structural And Magnetic Properties Of Transition-metal Doped TiO₂

As a wide band gap semiconductor, titanium oxide(TiO₂) films have been widely applicated in electronic devices, optical devices and solar cells due to their excellent chemical stability, optical properties, electrical properties and high photocatalytic efficiency. TiO₂-based magnetic semiconductor materials are expected to benefit the development of optical, electrical and magnetic devices and which has been attracting tremendous attention in recent years. In this work, we prepared TiO₂ thin films by changing the parameters of magnetron sputtering and the amount of doped metal, and studied their morphologies, crystal structure and magnetic properties.TiO₂ films were prepared on glass substrates by DC magnetron sputtering with the different substrate temperature in the range of 300℃-480℃, and then all the samples of TiO₂ films were annealed in the air. The results showed that the crystallization and the microstructure of TiO₂ films are greatly influenced by the substrate temperature. It was found that the anatase and rutile phases co-existed in the TiO₂ films deposited at 420℃,450℃,480℃, however, there was only the anatase phase existed in the samples deposited at other substrate temperatures.The samples of TiO₂ films, deposited with the substrates keeping at 150℃, were annealed in the different atmosphere. The rusults showed that the samples annealed in vacuum exhibited amorphous structure; the samples annealed in air or pure O2 exhibited anatase phase structures; the samples annealed in Ar showed complex phase of anatese and rutile.TiO₂ films were deposited with different ratio of O2:Ar at room temperature, and then the samples were annealed in air condition. The results showed that the samples exhibited rutile phase structure after annealed in mixed atmosphere of oxygen and argon with the relatively small quantity of oxygen; while it would be anatase phase structure after annealed in a same condition with the relatively big quantity of oxygen.Fe-TiO₂ and Co-TiO₂ films were prepared on glass substrates with the substrate temperature kept atc300℃. The samples as synthesized showed amorphous structure; however, the samples were annealed at 500℃for 1h in air showed better crystallization. There was a phase transformation by doping Fe or Co into TiO2 films and which would inhibit the crystallization of the samples with the increase of the amount of the doped metal element.Co-doped TiO2 films were prepared at room temperature. A room temperature ferromagnetism was observed in all the Co doped TiO2 thin films, and the magnetization increased on increasing the amount of dopants but on further doping it decreased. The largest magnetization of 11.2 emu/cm3 was observed when the Co content is 12%, while the largest coercivity value of 190 Oe was found in the sample with the Co content 9%.