Imaging of electrically controlled van der Waals layer stacking in 1T-TaS2

TL;DR

This study uses advanced X-ray imaging to reveal the spatial structure of electrically induced phase changes in 1T-TaS2, demonstrating non-filamentary, collective switching mechanisms relevant for low-power memory devices.

Contribution

It introduces a novel in operando X-ray imaging approach to visualize the bulk switching behavior and layer stacking in 1T-TaS2 during electrical control.

Findings

Revealed a long-range ordered, non-filamentary switched state

Demonstrated the collective growth driven by charge flow and lattice strain

Showcased the potential of 3D X-ray imaging for studying vdW materials

Abstract

Van der Waals (vdW) materials exhibit a variety of states that can be switched with low power at low temperatures, offering a viable cryogenic "flash memory" required for the classical control electronics for solid-state quantum information processing. In 1T-TaS2, a non-volatile metallic 'hidden' state can be induced from an insulating equilibrium charge-density wave ground state using either optical or electrical pulses. Given that conventional memristors form localized, filamentary channels which support the current, a key question for design concerns the geometry of the conduction region in highly energy-efficient 1T-TaS2 devices. Here, we report in operando micro-beam X-ray diffraction, fluorescence, and concurrent transport measurements, allowing us to spatially image the non-thermal hidden state induced by electrical switching of 1T-TaS2. Our results reveal a long-range ordered, non-filamentary switched state that extends well below the electrodes, implying that the self-organized, collective growth of the hidden phase is driven by a combination of charge flow and lattice strain. Our unique combination of techniques showcases the potential of non-destructive, three-dimensional X-ray imaging to study bulk switching properties in microscopic detail, namely electrical control of the vdW layer stacking.