Nanoscale control of an interfacial metal–insulator transition at room temperature

Abstract

Experimental1,2,3,4,5,6,7 and theoretical8,9 investigations have demonstrated that a quasi-two-dimensional electron gas (q-2DEG) can form at the interface between two insulators: non-polar SrTiO3 and polar LaTiO3 (ref. 2), LaAlO3 (refs 3–5), KTaO3 (ref. 7) or LaVO3 (ref. 6). Electronically, the situation is analogous to the q-2DEGs formed in semiconductor heterostructures by modulation doping. LaAlO3/SrTiO3 heterostructures have recently been shown10 to exhibit a hysteretic electric-field-induced metal–insulator quantum phase transition for LaAlO3 thicknesses of 3 unit cells. Here, we report the creation and erasure of nanoscale conducting regions at the interface between two insulating oxides, LaAlO3 and SrTiO3. Using voltages applied by a conducting atomic force microscope (AFM) probe, the buried LaAlO3/SrTiO3 interface is locally and reversibly switched between insulating and conducting states. Persistent field effects are observed using the AFM probe as a gate. Patterning of conducting lines with widths of 3 nm, as well as arrays of conducting islands with densities >1014 inch−2, is demonstrated. The patterned structures are stable for >24 h at room temperature.

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Figure 1: Writing and erasing nanowires at the LaAlO3/SrTiO3 interface.
Figure 2: Current–voltage characteristics of LaAlO3/SrTiO3 interface.
Figure 3: Measuring the limits of conducting island density.
Figure 4: Calculated LDOS of LaAlO3/SrTiO3 for ‘ideal’ and reduced LaAlO3 surfaces for each layer in the 3 unit cell LaAlO3 film and for the first four unit cells of the SrTiO3 substrate.

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Acknowledgements

We gratefully acknowledge helpful interactions and discussions with T. Kopp and S. K. Streiffer. Computations were carried out at the DoD Major Shared Resource Centers. This work was supported by DARPA DAAD-19-01-1-0650, NSF DMR-0704022, the DFG (SFB 484), the EC (Nanoxide) and the ESF (THIOX).

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Correspondence to J. Levy.

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Cen, C., Thiel, S., Hammerl, G. et al. Nanoscale control of an interfacial metal–insulator transition at room temperature. Nature Mater 7, 298–302 (2008). https://doi.org/10.1038/nmat2136

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