Strong Surface‐Termination Effect on Electroresistance in Ferroelectric Tunnel Junctions |
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| Authors: | Hiroyuki Yamada Atsushi Tsurumaki‐Fukuchi Masaki Kobayashi Takuro Nagai Yoshikiyo Toyosaki Hiroshi Kumigashira Akihito Sawa |
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| Affiliation: | 1. National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan;2. Japan Science and Technology Agency (JST), PRESTO, Kawaguchi, Saitama, Japan;3. Photon Factory, KEK, Tsukuba, Ibaraki, Japan;4. National Institute for Materials Science(NIMS), Tsukuba, Ibaraki, Japan |
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| Abstract: | Tunnel electroresistance in ferroelectric tunnel junctions (FTJs) has attracted considerable interest, because of a promising application to nonvolatile memories. Development of ferroelectric thin‐film devices requires atomic‐scale band‐structure engineering based on depolarization‐field effects at interfaces. By using FTJs consisting of ultrathin layers of the prototypical ferroelectric BaTiO3, it is demonstrated that the surface termination of the ferroelectric in contact with a simple‐metal electrode critically affects properties of electroresistance. BaTiO3 barrier‐layers with TiO2 or BaO terminations show opposing relationships between the polarization direction and the resistance state. The resistance‐switching ratio in the junctions can be remarkably enhanced up to 105% at room temperature, by artificially controlling the fraction of BaO termination. These results are explained in terms of the termination dependence of the depolarization field that is generated by a dead layer and imperfect charge screening. The findings on the mechanism of tunnel electroresistance should lead to performance improvements in the devices based on nanoscale ferroelectrics. |
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| Keywords: | electroresistance ferroelectric tunnel junctions metal– oxide interfaces surface termination |
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