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

Abstract

Experimental and theoretical 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 shown 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 approximately 3 nm, as well as arrays of conducting islands with densities >10(14) inch(-2), is demonstrated. The patterned structures are stable for >24 h at room temperature.

Magnetic and superconducting ordering in one-dimensional nanostructures at the LaAlO3/SrTiO3interface

“…The parameter K has a complicated dependence onK andṽ which follows from Eq. (31). However, at small initial velocity mismatch |δv| ≡ |v − v F | v F , one finds…”

“…Indeed, the fabrication of narrow quasi-one dimensional conducting channels on an otherwise insulating LAO/STO interface [31][32][33] by 'writing' them with an atomic-force microscope (AFM) tip suggests a natural implementation for the proposals of Refs. 29 and 30.…”

Control of electronic conduction at an oxide heterointerface using surface polar adsorbates

“…We note that in principle the biased scanning probe will also change the physical distribution of the adsorbates, (for example, water), in addition to chemical changes, which may also contribute to the modulation in the interface conductivity in the charge writing experiments [10][11][12][13] .…”

“…These include the use of conducting atomic force microscopy probes to toggle a metal insulator transition [10][11][12] through the writing of surface charge 12,13 , and the use of capping layers of SrTiO 3 (ref. 14) or SrCuO 2 (ref.…”

“…We have found that the exposure of LaAlO 3 /SrTiO 3 samples to a polar solvent can increase the sheet carrier density, n 2d , by more than 2×10 13 cm − 2 , representing a change of the same order as the total charge density typical in this system [5][6][7][8] . Compared with the strong perturbations associated with other surface processes, that is, the extremely strong local electric field produced by the conducting atomic force microscopy probes [10][11][12][13] , or the structural variation by introducing capping layers grown at high temperatures 14,15 , the changes associated with room-temperature treatment using these solvents would naively be expected to be small. However, such processes result in a surprisingly large modulation of n 2d , revealing a dramatic surface-interface coupling.…”