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An electron microscope's primary beam simultaneously ejects secondary electrons (SEs) from the sample and generates electron beam-induced currents (EBICs) in the sample. Both signals can be captured and digitized to produce images. The off-sample Everhart-Thornley detectors that are common in scanning electron microscopes (SEMs) can detect SEs with low noise and high bandwidth. However, the transimpedance amplifiers appropriate for detecting EBICs do not have such good performance, which makes accessing the benefits of EBIC imaging at high-resolution relatively more challenging. Here we report lattice-resolution imaging via detection of the EBIC produced by SE emission (SEEBIC). We use an aberration-corrected scanning transmission electron microscope (STEM), and image both microfabricated devices and standard calibration grids.

Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS2 heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.