School of Materials Science and Engineering, Kunming University of Science and Technology , Kunming 650093, PR China.
ACS Appl Mater Interfaces. 2017 Jan 25;9(3):3168-3177. doi: 10.1021/acsami.6b14726. Epub 2017 Jan 10.
The relative stability of multiferroic BiFeO (0001) surfaces, which is the (111) facet in the pseudocubic notation, with different stoichiometry is systematically studied by using ab initio thermodynamic approach in order to obtain insights into the stable surface terminations. We predict that under most chemical potential conditions the thermodynamically favored terminations for the negative and positive surfaces are -Bi-O and -Fe-O-Bi, respectively. The predicted difference in oxygen content between the negative and positive surfaces is consistent with experimental observations at the BiFeO/metal interfaces ( Nat. Mater. , 2014 , 13 , 1019 , DOI: 10.1038/nmat4058 ; Adv. Mater. , 2015 , 27 , 6934 , DOI: 10.1002/adma.201502754 ). We determine the atomic geometries and electronic states as well as the magnetic properties for the negatively and positively polarized stable surfaces. Our results demonstrate that not only the stoichiometry and atomic geometries but also the electronic and magnetic properties of the BiFeO (0001) surfaces show strong dependence on the ferroelectric polarization direction. Therefore, we expect that the surface physical and chemical properties of the BiFeO (0001) surfaces can be easily tuned by an external electric field.
采用从头算热力学方法系统研究了不同化学计量比的多铁 BiFeO(0001)表面（在赝立方记法中为(111)晶面）的相对稳定性，以便深入了解稳定的表面终端。我们预测，在大多数化学势条件下，负表面和正表面的热力学有利终端分别为-Bi-O 和 -Fe-O-Bi。预测的负表面和正表面之间的氧含量差异与 BiFeO/金属界面的实验观察结果一致（Nat. Mater., 2014, 13, 1019, DOI: 10.1038/nmat4058 ; Adv. Mater., 2015, 27, 6934, DOI: 10.1002/adma.201502754）。我们确定了负极化和正极化稳定表面的原子几何形状和电子态以及磁性质。我们的结果表明，不仅 BiFeO(0001)表面的化学计量比和原子几何形状，而且电子和磁性质都强烈依赖于铁电极化方向。因此，我们预计 BiFeO(0001)表面的表面物理和化学性质可以很容易地通过外部电场进行调节。
