In operando cryo-STEM of pulse-induced charge density wave switching in TaS$_2$

TL;DR

This study uses cryo-STEM to directly observe how pulse-induced switching in TaS$_2$ involves Joule heating and phase changes, revealing the role of defects and CDW structures in device performance.

Contribution

It provides the first in operando cryo-STEM visualization of CDW dynamics during switching, linking nanoscale structure changes to electrical resistance in TaS$_2$ devices.

Findings

Pulse-induced transition driven by Joule heating.

Switching involves nearly commensurate and incommensurate CDW phases.

Dislocations significantly affect device performance.

Abstract

The charge density wave (CDW) material 1T-TaS$_2$ exhibits a pulse-induced insulator-to-metal transition, which shows promise for next-generation electronics such as memristive memory and neuromorphic hardware. However, the rational design of TaS$_2$ devices is hindered by a poor understanding of the switching mechanism, the pulse-induced phase, and the influence of material defects. Here, we operate a 2-terminal TaS$_2$ device within a scanning transmission electron microscope (STEM) at cryogenic temperature, and directly visualize the changing CDW structure with nanoscale spatial resolution and down to 300 {\mu}s temporal resolution. We show that the pulse-induced transition is driven by Joule heating, and that the pulse-induced state corresponds to nearly commensurate and incommensurate CDW phases, depending on the applied voltage amplitude. With our in operando cryo-STEM experiments, we directly correlate the CDW structure with the device resistance, and show that dislocations significantly impact device performance. This work resolves fundamental questions of resistive switching in TaS$_2$ devices critical for engineering reliable and scalable TaS$_2$ electronics.