First-principles insights for high-resolution ion microscopy of graphene

The unique electronic properties of graphene allow many potential applications in novel electronic devices. However, these applications require high-resolution imaging of the 2D material to ensure a desirable atomic structure. The most precise available techniques detect emitted electrons as an ion beam scans the sample, resolving nanoscale features but struggling to achieve atomic resolution. First-principles modeling can accelerate experimental efforts to improve microscopy methods and offer detailed insights into underlying physics. Using timedependent density functional theory, we simulate 6-200 keV light ions traversing free-standing graphene along different trajectories. We then generate simulated microscopy images from the calculated entrance- and exit-side emitted electron yields. For incident protons, we find highest contrast for a 50 keV beam, and we predict higher contrast for exit-side (forward) emission than the typically detected entrance-side (backward) emission. We also compare contrast achieved by protons and alpha particles. These findings could enable higher resolution imaging of 2D materials, allowing precise screening for the structural properties required by applications.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.