Low-energy electron point projection microscopy/diffraction study of suspended graphene

Highlights: • An electron point projection microscopic/diffractive instrument was constructed. • It allows characterizing thickness, lattice orientations, and ripples of graphene. • Long-duration exposure to low energy electrons caused aggregation of adsorbates. - Abstract: In this work, we present our study of suspended graphene with low-energy electrons based on a point projection microscopic/diffractive imaging technique. Both exfoliated and chemical vapor deposition (CVD) graphene samples were studied in an ultra-high vacuum chamber. This method allows imaging of individual adsorbates at the nanometer scale and characterizing graphene layers, graphene lattice orientations, ripples on graphene membranes, etc. We found that long-duration exposure to low-energy electron beams induced aggregation of adsorbates on graphene when the electron dose rate was above a certain level. We also discuss the potential of this technique to conduct coherent diffractive imaging for determining the atomic structures of biological molecules adsorbed on suspended graphene.