Skewed electronic band structure induced by electric polarization in ferroelectric BaTiO3
Skewed electronic band structure induced by electric polarization in ferroelectric BaTiO3
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DOI：
10.1038/s41598-020-67651-w
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发表时间：
2020-07
影响因子：
4.6
通讯作者：
Norihiro Oshime;J. Kano;E. Ikenaga;S. Yasui;Yosuke Hamasaki;S. Yasuhara;S. Hinokuma;N. Ikeda;P. Janolin;J. Kiat;M. Itoh;T. Yokoya;T. Fujii;A. Yasui;H. Osawa
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作者：
Norihiro Oshime;J. Kano;E. Ikenaga;S. Yasui;Yosuke Hamasaki;S. Yasuhara;S. Hinokuma;N. Ikeda;P. Janolin;J. Kiat;M. Itoh;T. Yokoya;T. Fujii;A. Yasui;H. Osawa
铁电材料中的倾斜能带结构已经被经验性地描述，以解释最近开发的铁电隧道结（FTJ）的功能。非易失性铁电随机存储器（FeRAM）和基于FTJ系统的人工神经网络器件正在迅速发展。然而，由于实际的铁电能带结构还没有阐明，精确的器件设计，必须通过适当的化学先进。在这里，我们进行角分辨硬X射线光电子能谱的铁电BaTiO 3薄膜的原子轨道的深度剖面的铁电带倾斜结构的直接观察。深度分辨的电子能带结构由三个深度区域组成：一个电位斜率沿着在核心的电极化，表面和界面表现出轻微的变化。我们还证明了能量移动的方向是由极化反转控制的。在铁电倾斜能带结构中，我们发现原子轨道的能量移动的差异与反映Born有效电荷的软声子模的原子构型相关。这些发现有助于更好地理解电极化的起源。
Skewed band structures have been empirically described in ferroelectric materials to explain the functioning of recently developed ferroelectric tunneling junction (FTJs). Nonvolatile ferroelectric random access memory (FeRAM) and the artificial neural network device based on the FTJ system are rapidly developing. However, because the actual ferroelectric band structure has not been elucidated, precise designing of devices has to be advanced through appropriate heuristics. Here, we perform angle-resolved hard X-ray photoemission spectroscopy of ferroelectric BaTiO3thin films for the direct observation of ferroelectric band skewing structure as the depth profiles of atomic orbitals. The depth-resolved electronic band structure consists of three depth regions: a potential slope along the electric polarization in the core, the surface and interface exhibiting slight changes. We also demonstrate that the direction of the energy shift is controlled by the polarization reversal. In the ferroelectric skewed band structure, we found that the difference in energy shifts of the atomic orbitals is correlated with the atomic configuration of the soft phonon mode reflecting the Born effective charges. These findings lead to a better understanding of the origin of electric polarization.