Nanoscale Electrostatic Control of Oxide Interfaces

Abstract

We develop a robust and versatile platform to define nanostructures at oxide interfaces via patterned top gates. Using LaAlO3/SrTiO3 as a model system, we demonstrate controllable electrostatic confinement of electrons to nanoscale regions in the conducting interface. The excellent gate response, ultra-low leakage currents, and long term stability of these gates allow us to perform a variety of studies in different device geometries from room temperature down to 50 mK. Using a split-gate device we demonstrate the formation of a narrow conducting channel whose width can be controllably reduced via the application of appropriate gate voltages. We also show that a single narrow gate can be used to induce locally a superconducting to insulating transition. Furthermore, in the superconducting regime we see indications of a gate-voltage controlled Josephson effect.Despite decades of intense study, transition metal oxides continue to reveal fascinating and unexpected physical properties that arise from their highly correlated electrons [1]. Propelled by recent developments in oxides thin film technology it has now become possible to create high quality interfaces between such complex oxides, which reveal a new class of emergent phenomena often non-existent in the constituent materials [2,3]. In particular, there has been a growing interest in interfaces that host a conducting two dimensional electron system (2DES) [4,5]. This 2DES has been shown to support high mobility electrons [5][6][7], magnetism [8] and superconductivity [9]. In addition to this inherently rich phase space, in-situ electrostatic gating can be used not only to alter the carrier density [10], but it can significantly change the spin-orbit coupling (SOC) [11,12] and even drive transitions from a superconducting to an insulating state [13].Bulk transport studies of oxide interfaces have played an important role toward building a better understanding of these new material systems. However, it is becoming increasingly clear that in order to fully grasp the details of the complex coexisting phases at the interface, one must probe the system at much smaller length scales. Recent scanning probe experiments have indeed clearly demonstrated that the electronic properties of the interface can change dramatically over microscopic length scales [14][15][16]. In this context, nanoscale electronic devices could provide direct information on how such strong local variations in physical properties affect mesoscopic charge transport. Perhaps even more exciting is the possibility of discovering and manipulating new electronic states that are predicted to arise from the interplay between confinement, superconductivity and SOC [17]. Furthermore, the ability to locally drive phase transitions at the interface could potentially yield technologically relevant oxide-based nano-electronic devices with novel functionality [18].Existing methods for confinement at the interface involve some form of nanoscale patterning, which renders selected portions of the interface insulati...

Nanoscale patterning of electronic devices at the amorphous LaAlO3/SrTiO3 oxide interface using an electron sensitive polymer mask

“…Although the devices were operated in the regime close to pinch-off, no quantization of conductance nor signatures of conductance fluctuation were observed. This is similar to previous reports 27 and is interpreted as a current carried by many weakly transmitting transverse modes. Systematic investigations of device geometries varying the potential steepness around the channel may shed further light on this.…”

Gate-Tunable Band Structure of the LaAlO3−SrTiO3 Interface

“…Using this field effect, control of superconductivity [13][14][15][16][17], of spin-orbit coupling [17][18][19][20], and of carrier mobility [21,22] has been reported. Recent progress on local control of superconductivity [16] opened a route towards electrically controlled oxide Josephson junctions [23,24], providing new opportunities for superconducting electronic devices. Because these phenomena are related to the interfacial band structure, a fundamental understanding of the band structure is vital for the understanding of these phenomena and their exploitation in electronic devices.…”

Field-Effect Transistors with Submicrometer Gate Lengths Fabricated fromLaAlO3−SrTiO3-Based Heterostructures

“…FETs have been demonstrated with top gates [19,[21][22][23][24][25][26][27] as well as with side gates [28]. These transistors operate in a large temperature window which includes room temperature.…”