Evans Donald M, Holstad Theodor S, Mosberg Aleksander B, Småbråten Didrik R, Vullum Per Erik, Dadlani Anup L, Shapovalov Konstantin, Yan Zewu, Bourret Edith, Gao David, Akola Jaakko, Torgersen Jan, van Helvoort Antonius T J, Selbach Sverre M, Meier Dennis
Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Nat Mater. 2020 Nov;19(11):1195-1200. doi: 10.1038/s41563-020-0765-x. Epub 2020 Aug 17.
Utilizing quantum effects in complex oxides, such as magnetism, multiferroicity and superconductivity, requires atomic-level control of the material's structure and composition. In contrast, the continuous conductivity changes that enable artificial oxide-based synapses and multiconfigurational devices are driven by redox reactions and domain reconfigurations, which entail long-range ionic migration and changes in stoichiometry or structure. Although both concepts hold great technological potential, combined applications seem difficult due to the mutually exclusive requirements. Here we demonstrate a route to overcome this limitation by controlling the conductivity in the functional oxide hexagonal Er(Mn,Ti)O by using conductive atomic force microscopy to generate electric-field induced anti-Frenkel defects, that is, charge-neutral interstitial-vacancy pairs. These defects are generated with nanoscale spatial precision to locally enhance the electronic hopping conductivity by orders of magnitude without disturbing the ferroelectric order. We explain the non-volatile effects using density functional theory and discuss its universality, suggesting an alternative dimension to functional oxides and the development of multifunctional devices for next-generation nanotechnology.
利用复杂氧化物中的量子效应，如磁性、多铁性和超导性，需要对材料的结构和成分进行原子级控制。相比之下，实现基于人工氧化物的突触和多组态器件的连续导电性变化是由氧化还原反应和畴重构驱动的，这涉及长程离子迁移以及化学计量或结构的变化。尽管这两个概念都具有巨大的技术潜力，但由于相互排斥的要求，联合应用似乎很困难。在这里，我们展示了一条克服这一限制的途径，即通过使用导电原子力显微镜在功能性氧化物六方Er(Mn,Ti)O中控制导电性，以产生电场诱导的反弗伦克尔缺陷，即电荷中性的间隙-空位对。这些缺陷以纳米级空间精度产生，以在不干扰铁电序的情况下将电子跳跃传导率局部提高几个数量级。我们使用密度泛函理论解释了非易失性效应，并讨论了其普遍性，这为功能性氧化物和下一代纳米技术的多功能器件的发展提供了一个新的维度。
