Imaging and tuning polarity at SrTiO3 domain walls

Abstract

Electrostatic fields tune the ground state of interfaces between complex oxide materials. Electronic properties, such as conductivity and superconductivity, can be tuned and then used to create and control circuit elements and gate-defined devices. Here we show that naturally occurring twin boundaries, with properties that are different from their surrounding bulk, can tune the LaAlO/SrTiO interface 2DEG at the nanoscale. In particular, SrTiO domain boundaries have the unusual distinction of remaining highly mobile down to low temperatures, and were recently suggested to be polar. Here we apply localized pressure to an individual SrTiO twin boundary and detect a change in LaAlO/SrTiO interface current distribution. Our data directly confirm the existence of polarity at the twin boundaries, and demonstrate that they can serve as effective tunable gates. As the location of SrTiO domain walls can be controlled using external field stimuli, our findings suggest a novel approach to manipulate SrTiO-based devices on the nanoscale.

Incipient ferroelectricity: A route towards bulk-terminated SrTiO3

“…The surface termination can only switch at ferroelectric domain walls, which, at the surface, are associated with very large steps. The observed domain size is in the few µm range, and the orientation of the steps is consistent with observations made on various thin films grown on SrTiO 3 , where the domain walls run along the main crystallographic directions and linear combinations thereof [27][28][29].…”

Low-Temperature Dielectric Anisotropy Driven by an Antiferroelectric Mode in SrTiO3

“…To explore this route, however, one first needs to understand whether (and how) the ferroelastic degrees of freedom can be harnessed via a suitable external field. As the ferroelastic domain walls have recently been shown to be polar [16][17][18][19][20][21][22], it is reasonable to expect that they will respond to an electrical bias. A detailed study on the evolution of the domain wall topology upon application of a voltage is currently missing, leaving the above question largely unanswered.…”

Bimodal Phase Diagram of the Superfluid Density in LaAlO3/SrTiO3 Revealed by an Interfacial Waveguide Resonator

“…However, the spatial resolution is not sufficient to simultaneously image the current paths and the domain boundaries; the size of the latter does not exceed 500-600 nm. Estimations of the wall (twins, dislocations) widths in the bundles reported by several authors are between few tens of nanometers [44,45] and 1-10 nm [48,49]. If the conducting channel consists of a bundle of filaments of micrometer size, one could consider each filament as forming a junction neighbouring filaments being separated by 10 nm walls.…”