Wu Tai-Sing, Syu Leng-You, Lin Bi-Hsuan, Weng Shih-Chang, Jeng Horng-Tay, Huang Yu-Shan, Soo Yun-Liang
National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Sci Rep. 2021 Apr 7;11(1):7668. doi: 10.1038/s41598-021-87115-z.
We report the experimental observation of and theoretical explanation for the reduction of dopant ions and enhancement of magnetic properties in Ce-doped TiO diluted magnetic semiconductors from UV-light irradiation. Substantial increase in Ce concentration and creation of oxygen vacancy defects in the sample due to UV-light irradiation was observed by X-ray and optical methods. Magnetic measurements demonstrate a combination of paramagnetism and ferromagnetism up to room temperatures in all samples. The magnetization of both paramagnetic and ferromagnetic components was observed to be dramatically enhanced in the irradiated sample. First-principle theoretical calculations show that valence holes created by UV irradiation can substantially lower the formation energy of oxygen vacancies. While the electron spin densities for defect states near oxygen vacancies in pure TiO are in antiferromagnetic orientation, they are in ferromagnetic orientations in Ce-doped TiO. Therefore, the ferromagnetically-oriented spin densities near oxygen vacancies created by UV irradiation are the most probable cause for the experimentally observed enhancement of magnetism in the irradiated Ce-doped TiO.
我们报告了在紫外光照射下，铈掺杂二氧化钛稀磁半导体中掺杂离子减少和磁性能增强的实验观察结果及理论解释。通过X射线和光学方法观察到，由于紫外光照射，样品中铈浓度大幅增加且产生了氧空位缺陷。磁性测量表明，所有样品在室温以下都呈现顺磁性和铁磁性的组合。在辐照样品中，顺磁性和铁磁性成分的磁化强度均显著增强。第一性原理理论计算表明，紫外光照射产生的价带空穴可大幅降低氧空位的形成能。虽然纯二氧化钛中氧空位附近缺陷态的电子自旋密度呈反铁磁取向，但在铈掺杂二氧化钛中呈铁磁取向。因此，紫外光照射产生的氧空位附近的铁磁取向自旋密度是实验观察到的辐照铈掺杂二氧化钛磁性增强的最可能原因。
