Conductivity control via minimally invasive anti-Frenkel defects in a functional oxide

• Published in: Nature materials 2020-11, Vol.19 (11), p.1195-1200
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: 639/301; 639/301/119/995; 639/301/119/996; 639/925; Atomic force microscopy; Biomaterials; Chemistry and Materials Science; Condensed Matter Physics; Conductivity; Density functional theory; Electric fields; Electrical resistivity; Ferroelectricity; Frenkel defects; Hopping conduction; Ion migration; Laboratories; Magnetism; Materials Science; Microscopy; Nanotechnology; Optical and Electronic Materials; Oxides; Physics; Redox reactions; Stoichiometry; Structural integrity; Superconductivity; Synapses; Writing
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-020-0765-x

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 3 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. Combining quantum effects with conductivity modulation in complex oxides requires mutually exclusive criteria, making applications difficult. Using tip-induced electrical generation of anti-Frenkel defects, conducting features in Er(Mn,Ti)O 3 are written with nanoscale precision while keeping structural integrity.