Simultaneous Atomic Resolution Imaging and Electrical Characterization of 2D Quantum Devices

Direct correlation between (opto-/magneto-)electronic properties and structure is critical for the understanding of nanoscale and quantum devices. Recent developments in (scanning) transmission electron microscopy (S/TEM) allow acquisition of atomic resolution images at cryogenic temperatures while measuring electrical properties. The S/TEM therefore acts as a cryostat with added functionalities such as imaging, 4D STEM and electron energy loss spectroscopy to investigate excitations. We present our progress towards in-situ electrical characterization of 2D quantum devices.<br/><br/>Electronic properties of 2D materials are commonly measured using graphene/BN/X/BN heterostructures, where graphene is the gate electrode, BN the dielectric, and in our case X=WSe₂, MoS₂, Cr₂Ge₂Te₆. It is necessary to understand beam effects when imaging these samples. The electrical properties of nanoscale devices are extremely sensitive towards the edge configuration, e.g. edge termination, zigzag or armchair, and the edge roughness. If the X layers are patterned, imaging could change their structure. We use atomic mass contrast to obtain atomic resolution images of the X layers and show that that atomic rearrangements at edges and defects depend on the beam current and acceleration voltage. We, furthermore, obtain real time videos of W atoms diffusing in the van der Waals gap between BN and WSe₂ providing insights into atom diffusion in highly confined spaces.