UV-irradiation-enhanced room-temperature ferromagnetism in Ce-doped TiO2 nanocrystals

Tai-Sing Wu^1*, Horng-Tay Jeng¹, Shih-Lin Chang^1,2, Yun-Liang Soo^1,2

¹Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Tai-Sing Wu, email:wts4832@gmail.com

UV-irradiation-enhanced room-temperature ferromagnetism has been experimentally observed in Ce-doped TiO2 nanocrystals. As demonstrated by synchrotron-based x-ray absorption analysis, the valence of Ce dopant atoms was effectively reduced after UV-light irradiation, while the Ti valence remains largely unchanged. The physical mechanism underlying such effect has been theoretically investigated by DFT calculations. A simple model is proposed to explain such intriguing interplay between the effects of photon irradiation and Ce valence reduction in these cerium doped systems. In addition, a decreased energy gap value due to the band tailing effect incurred by photon irradiation is observed. The irradiation induced band gap narrowing provides an ultraconvenient method for band gap engineering in TiO2 for photocatalytic applications.

Keywords: defect engineering, magnetic semiconductor, XAFS, DFT