Ionic liquid gating of SrTiO$_3$ lamellas fabricated with a focused ion beam

TL;DR

This paper demonstrates a method combining focused ion beam shaping and ionic liquid gating to create pristine, patterned two-dimensional charge carrier systems on SrTiO3 lamellas, enabling new device fabrication possibilities.

Contribution

It introduces a protective layer technique to preserve surface quality during FIB fabrication, allowing effective ionic liquid gating on micro-scale crystals.

Findings

Superconductivity observed in gated SrTiO3 lamellas.

Surface damage minimized enabling charge accumulation.

Patterned electrostatic charge tuning demonstrated.

Abstract

In this work, we combine two previously-incompatible techniques for defining electronic devices: shaping three-dimensional crystals by focused ion beam (FIB), and two-dimensional electrostatic accumulation of charge carriers. The principal challenge for this integration is nanometer-scale surface damage inherent to any FIB-based fabrication. We address this by using a sacrificial protective layer to preserve a selected pristine surface. The test case presented here is accumulation of 2D carriers by ionic liquid gating at the surface of a micron-scale SrTiO$_3$ lamella. Preservation of surface quality is reflected in superconductivity of the accumulated carriers. This technique opens new avenues for realizing electrostatic charge tuning in materials that are not available as large or exfoliatable single crystals, and for patterning the geometry of the accumulated carriers.