Wei Jiake, Ogawa Takafumi, Feng Bin, Yokoi Tatsuya, Ishikawa Ryo, Kuwabara Akihide, Matsunaga Katsuyuki, Shibata Naoya, Ikuhara Yuichi
Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan.
Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan.
Nano Lett. 2020 Apr 8;20(4):2530-2536. doi: 10.1021/acs.nanolett.9b05298. Epub 2020 Mar 5.
Grain boundaries (GBs) modulate the macroscopic properties in polycrystalline materials because they have different atomic and electronic structures from the bulk. Despite the progress on the understanding of GB atomic structures, knowledge of the localized electronic band structures is still lacking. Here, we experimentally characterized the atomic structures and the band gaps of four typical GBs in α-AlO by scanning transmission electron microscopy and valence electron energy-loss spectroscopy (EELS). It was found that the band gaps of the GBs are narrowed by 0.5-2.1 eV compared with that of 8.8 eV in the bulk. By combing core-loss EELS with first-principles calculations, we elucidated that the band gap reductions directly correlate with the decrease of the coordination numbers of Al and O ions at the GBs. These results provide in-depth understanding between the local atomic and electronic band structures for GBs and demonstrate a novel electronic-structure analysis for crystalline defects.
晶界（GBs）会调节多晶材料的宏观性质，因为它们具有与块体不同的原子和电子结构。尽管在理解晶界原子结构方面取得了进展，但对局部电子能带结构的认识仍然不足。在这里，我们通过扫描透射电子显微镜和价电子能量损失谱（EELS），对α - AlO中四种典型晶界的原子结构和带隙进行了实验表征。结果发现，与块体中8.8 eV的带隙相比，晶界的带隙缩小了0.5 - 2.1 eV。通过将芯损失EELS与第一性原理计算相结合，我们阐明了带隙的减小与晶界处Al和O离子配位数的减少直接相关。这些结果为深入理解晶界的局部原子和电子能带结构提供了依据，并展示了一种用于晶体缺陷的新型电子结构分析方法。
