Light-Induced Phase Transformations in Mixed-Phase BiFeO3
Yu-You Chiou1*, Yi-Chun Chen1, Ying-Hao Chu2, Jan-Chi Yang1
1Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
2Department of Material Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
* presenting author:Yu-You Chiou,
The physical properties of crystals are predominately determined by the group symmetry of the crystal lattice. As a result, a change of crystal lattice would directly result in the corresponding modification of physical properties in crystals, while the tunability of crystal lattice via external stimuli provides a pathway to control the functionalities of crystal.
Multiferroic BiFeO3 has both ferroelectric and antiferromagnetic properties at room temperature, which serves as a promising candidate for next-generation nanoelectronics. When the BiFeO3 is grown on LaAlO3, it becomes a mixed-phase system which is composed of tetragonal-like (T-like) and rhombohedral-like (R-like) phases. It is worth mentioning that the phase transition energy in such system is low so that we can control the phase by applying an electric field or stress according to the previous researches. In this study, we propose a new method to control these two phases and the resulting morphotropic phase boundaries via the illumination of 532 nm laser. AFM (atomic force microscopy) is adapted to modulate the as-grown mixed phase into pure T-like phase as the initial state. Our result shows that the center of laser spot prefers to adapt the T-like phase whereas the edge of laser spot favors the R-like phase. As the power becomes stronger, the domain wall of T-like phase shows a 90 degrees rotation and while R-like phase grows perpendicular to the T-like phase. Moreover, we can control the T-like phase by moving the laser spot along different directions. Through the elegant control of stimulation process, not only we offer an efficient way to control the lattice structure of complex materials, but also a pavement towards photonic modulation of multifunctionalities.

Keywords: Morphotropic phase boundaries, Multiferroics, BiFeO3, Phase transformation, Light