The Structural,Magnetic And Optical Studies Of Cr/N Codoped TiO₂ Thin Films

The semiconductor material plays a very important role in the era of information development. TiO₂ is widely used in the photovoltatic devices and solar cell applications because of its chemical stability, non-toxicity, low cost, and other advantageous properties. The simultaneous control of the magnetism and band gap of TiO₂ will expand its functions in new materials in the future. In this paper, the Cr/N codoped TiO₂ films were deposited by the pulsed laser deposition technique. The n-p codoping mechanism on the dual role of magnetism and band gap of TiO₂ has been stated through the analysis of the structure, morphology, magnetic and optical properties of films. The results are summarized as follows:?1? The Cr doped TiO₂ films were deposited by pulsed laser deposition and the structural, magnetic and optical properties of films were studied. The results show that the structure of films is related to the content of Cr. The higher Cr doping content would lead to phase transition and accelerate the rutile formation. The Cr doped TiO₂ films exhibit intrinsic ferromagnetism at room temperature. The blue shift of optical absorption edge of TiO₂ has been observed, and the minimum value of band gap is 3.09 e V for the maximum content of Cr. The absorption band in visible light region should be assigned to the Cr3+ ? Ti4+ charge transfer and 4A2 g ? 4T1 g transition of Cr3+ in an octahedral environment.?2? The Ti0.90Cr0.10O2/N films were grown on Sr Ti O3?100? substrates using pulsed laser deposition method. The effect of N doping on the structure, morphology and crystal phase of the films was systematically investigated. The results show that higher temperature is helpful to the quality of films by accelerating the growth of grains. The N doping not only makes the film crystallization poor, but also accelerates the rutile formation of the Cr/N codoped TiO₂ films. The experimental results also show that faster deposition rate is an important factor to the formation of rutile phase.?3? A series of Cr/N codoped anatase TiO₂ films with different doping contents have been grown using pulsed laser deposition technology. This work mainly expounds the important function of n-p codoping approach on the magnetism and band gap of TiO₂ film. The Ti1-xCrxO2/N?x=0.03, 0.06, 0.1? anatase films which have homogeneous structure had been prepared, and the presence of Cr3+ and N3- ions confirmed that the Cr and N atoms have replaced Ti and O in the TiO₂ lattice. Compared with pure TiO₂, Cr doped and N doped TiO₂ films, the saturation magnetization of Cr/N codoped TiO₂ is higher than Cr doped TiO₂. Moreover, the Cr/N codoping greatly increases the absorption of TiO₂ films in visible region and widens the absorption range to a certain extent. The band gap Cr/N codoped anatase TiO₂ has been reduced to 2.18 e V compared to the pure TiO₂. The enhanced ferromagnetism and reduced band gap of Cr/N codoped TiO₂ may be attributed to the defect energy levels of oxygen vacancies and Cr-N interaction.Anyway, we prepared Cr/N codoped TiO₂ films with different doping contents and studied the structural, magnetic and optical properties of films. The results reveal that non-compensation n-p codoping plays an important role on tuning the magnetic and optical properties. The TiO₂ material with simultaneous control of magnetism and optical band gap will have a very wide application prospect in the future.