Efficient elastic imaging of single atoms on ultrathin supports in a scanning transmission electron microscope.

Mono-atomic-layer membranes such as graphene offer new opportunities for imaging and detecting individual light atoms in transmission electron microscopes (TEM). For such applications where multiple scattering and diffraction effects are weak, we evaluate the detection efficiency and interpretability of single atom images for the most common detector geometries using quantitative quantum mechanical simulations. For well-resolved and atomically-thin specimens, the low angle annular dark field (LAADF) detector can provide a significant increase in signal-to-noise over other common detector geometries including annular bright field and incoherent bright field. This dramatically improves the visibility of organic specimens on atomic-layer membranes. Simulations of Adenosine Triphosphate (ATP) imaged under ideal conditions indicate the minimal dose requirements for elastic imaging by STEM or conventional TEM still exceed previously reported dose limits.