Imaging Secondary Electron Emission from a Single Atomic Layer

Abstract

Graphene‐based devices hold promise for a wide range of technological applications. Yet characterizing the structure and the electrical properties of a material that is only one atomic layer thick still poses technical challenges. Recent investigations indicate that secondary‐electron electron‐beam‐induced current (SE‐EBIC) imaging can reveal subtle details regarding electrical conductivity and electron transport with high spatial resolution. Here, it is shown that the SEEBIC imaging mode can be used to detect suspended single layers of graphene and distinguish between different numbers of layers. Pristine and contaminated areas of graphene are also compared to show that pristine graphene exhibits a substantially lower SE yield than contaminated regions. This SEEBIC imaging mode may provide valuable information for the engineering of surface coatings where SE yield is a priority.

Contrast Mechanisms in Secondary Electron e-Beam-Induced Current (SEEBIC) Imaging

“…The mean current values obtained for each region are listed above the corresponding bars in pA. We note that this suspended graphene is not clean graphene and thus the SEEBIC intensity is significantly increased. A previous publication measured an approximately fourfold increase in signal from contaminated regions (Dyck et al, 2021 b ).…”

“…The SEEBIC signal exhibited a significant interference component, which was synced with the electrical mains manifesting as vertical stripes. This signal was removed from all images presented here in a procedure fully described in the Supplementary Information of a previous publication (Dyck et al, 2021a(Dyck et al, , 2021b. Briefly, a script was used to sum the images vertically and obtain a moving average that represents the larger-scale image features (background intensity).…”

“…In this work, lattice-resolution images were acquired of Au nanoparticles on silicon nitride membranes. A recent publication in 2021 showed that the SEEBIC technique was sensitive enough to distinguish single layers of suspended graphene, despite its very low SE yield (Dyck et al, 2021 b ). Utilization of the SEEBIC technique for characterizing graphene-based nanoelectronic devices was also presented in 2021, where the authors noted SEEBIC-based detection of conductance switching in graphene nanoconstrictions (Dyck et al, 2021 a ).…”

Controlling hydrocarbon transport and electron beam induced deposition on single layer graphene: Toward atomic scale synthesis in the scanning transmission electron microscope

“…[28,29] By taking the idea of a reduced substrate thickness to the logical monolayer limit, one can envision working with graphene as the substrate [30] which is only one atom thick and is known to have a very low SE yield. [31][32][33] Working in this regime, van Dorp et al deposited nanodots from a W(CO) 6 precursor molecule-by-molecule to achieve deposits having dimensions less than 1 nm. [34] It becomes increasingly apparent, however, that extraneous material in the form of volatile hydrocarbons becomes a concern especially as the physical dimensions of the deposition site are edging toward the fundamental limit of single atoms.…”

Electron Beam Control of Dopants in 2D and 3D Materials

“…Similarly, it might be possible to map the functionality, such as conductivity at high spatial resolution. Recent results have shown that secondary-electron electron-beam-induced current imaging can detect even single monolayers of graphene [11]. Perhaps the next challenge will be not just to use the electron beam to image dopants, but to combine with machine learning and functional imaging modes to unveil and control their physical properties atom-by-atom [12,13].…”