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The charge density wave material 1T-TaS₂exhibits 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 TaS₂devices 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 TaS₂device within a scanning transmission electron microscope at cryogenic temperature, and directly visualize the changing charge density wave structure with nanoscale spatial resolution and down to 300 μs temporal resolution. We show that the pulse-induced transition is driven by Joule heating, and that the pulse-induced state corresponds to the nearly commensurate and incommensurate charge density wave phases, depending on the applied voltage amplitude. With our in operando cryogenic electron microscopy experiments, we directly correlate the charge density wave structure with the device resistance, and show that dislocations significantly impact device performance. This work resolves fundamental questions of resistive switching in TaS₂devices, critical for engineering reliable and scalable TaS₂electronics.

The layer stacking order in 2D materials strongly affects functional properties and holds promise for next-generation electronic devices. In bulk, octahedral MoTe₂possesses two stacking arrangements, the ferroelectric Weyl semimetal T_dphase and the higher-order topological insulator 1T′ phase. However, in thin flakes of MoTe₂, it is unclear if the layer stacking follows the T_d, 1T′, or an alternative stacking sequence. Here, we use atomic-resolution scanning transmission electron microscopy to directly visualize the MoTe₂layer stacking. In thin flakes, we observe highly disordered stacking, with nanoscale 1T′ and T_ddomains, as well as alternative stacking arrangements not found in the bulk. We attribute these findings to intrinsic confinement effects on the MoTe₂stacking-dependent free energy. Our results are important for the understanding of exotic physics displayed in MoTe₂flakes. More broadly, this work suggestsc-axis confinement as a method to influence layer stacking in other 2D materials.

With shrinking dimensions in integrated circuits, sensors, and functional devices, there is a pressing need to develop nanofabrication techniques with simultaneous control of morphology, microstructure, and material composition over wafer length scales. Current techniques are largely unable to meet all these conditions, suffering from poor control of morphology and defect structure or requiring extensive optimization or post‐processing to achieve desired nanostructures. Recently, thermomechanical nanomolding (TMNM) has been shown to yield single‐crystalline, high aspect ratio nanowires of metals, alloys, and intermetallics over wafer‐scale distances. Here, TMNM is extended for wafer‐scale fabrication of 2D nanostructures. Using In, Al, and Cu, nanomold nanoribbons with widths < 50 nm, depths ≈0.5–1 µm and lengths ≈7 mm into Si trenches at conditions compatible is successfully with back end of line processing . Through SEM cross‐section imaging and 4D‐STEM grain orientation maps, it is shown that the grain size of the bulk feedstock is transferred to the nanomolded structures up to and including single crystal Cu. Based on the retained microstructures of molded 2D Cu, the deformation mechanism during molding for 2D TMNM is discussed.