Takizawa M, Hotta Y, Susaki T, Ishida Y, Wadati H, Takata Y, Horiba K, Matsunami M, Shin S, Yabashi M, Tamasaku K, Nishino Y, Ishikawa T, Fujimori A, Hwang H Y
Department of Physics, University of Tokyo, 3-7-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Phys Rev Lett. 2009 Jun 12;102(23):236401. doi: 10.1103/PhysRevLett.102.236401. Epub 2009 Jun 10.
We have studied the valence redistribution of V in LaAlO(3)/LaVO(3)/LaAlO(3) trilayers, which are composed of only polar layers grown on SrTiO3 (001) substrates, by core-level photoemission spectroscopy. We have found that the V valence is intermediate between V3+ and V4+ for thin LaAlO3 cap layers, decreases with increasing cap-layer thickness, and finally recovers the bulk value of V3+ at approximately 10 unit-cell thickness. In order to interpret these results, we propose that the atomic reconstruction of the polar LaAlO3 surface competes with the purely electronic V valence change so that the polar catastrophe is avoided at the cost of minimum energy.
我们通过芯能级光电子能谱研究了生长在SrTiO3(001)衬底上仅由极性层组成的LaAlO(3)/LaVO(3)/LaAlO(3)三层结构中V的价态再分布。我们发现，对于薄的LaAlO3帽层，V的价态介于V3+和V4+之间，随着帽层厚度增加而降低，最终在约10个晶胞厚度时恢复到V3+的体相值。为了解释这些结果，我们提出极性LaAlO3表面的原子重构与纯粹的电子V价态变化相互竞争，从而以最低能量为代价避免了极性灾难。
