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.

Electronic confinement at nanoscale dimensions remains a central means of science and technology. We demonstrate nanoscale lateral confinement of a quasi-two-dimensional electron gas at a lanthanum aluminate-strontium titanate interface. Control of this confinement using an atomic force microscope lithography technique enabled us to create tunnel junctions and field-effect transistors with characteristic dimensions as small as 2 nanometers. These electronic devices can be modified or erased without the need for complex lithographic procedures. Our on-demand nanoelectronics fabrication platform has the potential for widespread technological application.

Metal oxide semiconductor field-effect transistors, formed using silicon dioxide and silicon, have undergone four decades of staggering technological advancement. With fundamental limits to this technology close at hand, alternatives to silicon dioxide are being pursued to enable new functionality and device architectures. We achieved ferroelectric functionality in intimate contact with silicon by growing coherently strained strontium titanate (SrTiO3) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. We observed ferroelectricity in these ultrathin SrTiO3 layers by means of piezoresponse force microscopy. Stable ferroelectric nanodomains created in SrTiO3 were observed at temperatures as high as 400 kelvin.

Abstract:Nanoscale control of the metal-insulator transition in LaAlO 3 / SrTiO 3 heterostructures can be achieved using local voltages applied by a conductive atomic-force microscope probe. One proposed mechanism for the writing and erasing process involves an adsorbed H 2 O layer at the top LaAlO 3 surface. In this picture, water molecules dissociates into OH -and H + which are then selectively removed by a biased AFM probe. To test this mechanism, writing and erasing experiments are performed in a vacuum AFM using various gas mixtures. Writing ability is suppressed in those environments where H 2 O is not present. The stability of written nanostructures is found to be strongly associated with the ambient environment. The self-erasure process in air can be strongly suppressed by creating a modest vacuum or replacing the humid air with dry inert gas. These experiments provide strong constraints for theories of both the writing process as well as the origin of interfacial conductance. an insulating state. We refer to this process as a "water cycle" because it permits multiple writing and erasing without physical modification of the oxide heterostructure.Here we investigate the writing and erasing process on 3uc-LAO/STO heterostructures under a variety of atmospheric conditions, in order to constrain physical models of the writing and erasing procedure and the origin of the interfacial electron gas. Thin films (3 u.c.) of LaAlO 3 were deposited on a TiO 2 -terminated (001) SrTiO 3 substrates by pulsed laser deposition with in situ high pressure reflection high energy electron diffraction (RHEED) [18]. Growth was at a temperature of 550°C and O 2 pressure of 1×10 -3 Torr. 4After growth, electrical contacts to the interface were prepared by milling 25nm deep trenches via an Ar-ion mill and filling them with Au/Ti bilayer (2nm adhesion Ti layer and 23nm Au layer).To perform c-AFM experiments, a vacuum AFM ( FIG. 1(a)) is employed that is capable of operation down to 10 -5 Torr and allows controlled introduction of various gases. Writing and erasing experiments (