Electrical domain writing and nanoscale potential modulation on LaVO3/SrTiO3

Abstract

The high-mobility 2DEGs formed at the interfaces between certain insulating perovskite oxides have been known to be a novel playground of exotic physical orders like, superconductivity and ferromagnetism and their inter-coupling. There have been efforts to accomplish even more exotic properties at such interfaces of oxide heterostructures through nano-structuring of the surface.In this paper we report writing and erasing charge domains on such an oxide heterostructure LaVO 3 /SrTiO 3 using a conductive AFM cantilever. We have patterned these domains in a periodic fashion in order to create artificial lattices on the surface. Through kelvin probe microscopy, electrostatic force microscopy and conductivity mapping of such artificial lattices we found that the domains not only trap charge carriers but also develop a controllable potential landscape on the surface which coincides with a modulation of local electrical conductivity. The ability to pattern such nanostructures reversibly offers unprecedented opportunities of realizing ultra-high storage density devices in high mobility oxide heterostructures.

Electrically Controlled Quantum Transition to an Anomalous Metal in 2D

“…Pronounced electric-field dependent phase switching in PFM signal was indeed seen in LaVO 3 /SrTiO 3 with thin (10 monolayers) of LaVO 3 . 32 Considering the above and noting the similarity of the observed effect with the electric field control of ferroelectric domains in ferroelectrics, it is rational to surmise that in the case of LaVO 3 /SrTiO 3 interfaces, the SrTiO 3 side of the interface hosts ferroelectric domains with out-of-plane spontaneous electric polarization. Our model would be applicable regardless of the origin of ferroelectric domains in SrTiO 3 .…”

“…We had earlier shown that electric domains can be written and erased on SrTiO 3 and LaVO 3 /SrTiO 3 controllably by an external electric field applied through a conducting cantilever in the socalled piezoresponse force microscopy (PFM) mode. 32 Here, it is important to note that SrTiO 3 is a known quantum paraelectric and exists very close to a ferroelectric phase transition. 25 A natural transition to a ferroelectric phase in SrTiO 3 is prevented by quantum fluctuations, but such a transition is easily facilitated by strain.…”

“…19−23 As the superconductivity of δ-doped SrTiO 3 is trapped in 2D when LaAlO 3 or LaVO 3 is deposited on SrTiO 3 , ferroelectricity also persists underneath such interfaces. 24,28,29,32 In such cases, the primary origin of interfacial strain is related to a structural phase transition of the SrTiO 3 substrate below 105 K from the high-temperature cubic to low-temperature tetragonal phase. 23,33 Ferroelectric domains in SrTiO 3 are also seen near intrinsic crystal defects like the twin boundaries or other forms of local mechanical disorder.…”

“…Even at room temperature, a few atomic layers near the surface give a ferroelectric response in piezoresponse force microscopy (PFM). , It is also widely believed that the pairing glue for surprising superconductivity in dilute δ-doped SrTiO 3 is mediated by ferroelectric fluctuations. A large volume of literature suggests that ferroelectricity and superconductivity are intimately related in SrTiO 3 . − As the superconductivity of δ-doped SrTiO 3 is trapped in 2D when LaAlO 3 or LaVO 3 is deposited on SrTiO 3 , ferroelectricity also persists underneath such interfaces. ,,, In such cases, the primary origin of interfacial strain is related to a structural phase transition of the SrTiO 3 substrate below 105 K from the high-temperature cubic to low-temperature tetragonal phase. , Ferroelectric domains in SrTiO 3 are also seen near intrinsic crystal defects like the twin boundaries or other forms of local mechanical disorder. ,− The phase boundary separating the nonferroelectric and the ferroelectric phases of SrTiO 3 is extremely narrow for expansive strain. Since the lattice constant of LaVO 3 (3.95 Å) is larger than that of SrTiO 3 , and that SrTiO 3 undergoes a structural phase transition below 105 K, the SrTiO 3 side of the LaVO 3 /SrTiO 3 interfaces is significantly strained and can host strong ferroelectricity.…”

Light-enhanced gating effect at the interface of oxide heterostructure

“…Over the past few decades, oxides have been playing an important role in the discoveries of emergent phenomena like high temperature superconductivity, multiferroics, colossal magnetoresistance and so on. [1][2][3][4][5][6][7][8][9] The field of oxide based electronic devices received a special attention after the discovery of two dimensional electron gas (2DEG) at the interface of two band insulating oxides namely LaAlO 3 (LAO) and SrTiO 3 (STO). 10 This simple interface exhibits wealth of phenomenona including quantum oscillations in conductivity, superconductivity, magnetism, large Rashba spin-orbit coupling, electric field effect, persistance photocurrent etc.…”