Analysis of Point Defects in Graphene Using Low Dose Scanning Transmission Electron Microscopy Imaging and Maximum Likelihood Reconstruction

• Published in: physica status solidi (b) Vol. 254; no. 11
• Main Authors: Kramberger, Christian, Mittelberger, Andreas, Hofer, Christoph, Meyer, Jannik C.
• Format: Journal Article
• Language: English
• Published: 01.11.2017
• Subjects: graphene; point defects; scanning transmission electron microscopy
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201700176

Freestanding graphene displays an outstanding resilience to electron irradiation at low electron energies. Point defects in graphene are, however, subject to beam driven dynamics. This means that high resolution micrographs of point defects, which usually require a high electron irradiation dose might not represent the intrinsic defect population. Here, we capture the initial defects formed by ejecting carbon atoms under electron irradiation, by imaging with very low doses and subsequent reconstruction of the frequently occuring defects via a maximum likelihood algorithm. Looking without touching is harder than one might think, especially with an electron microscope. Less electron bombardment means noisy data. Neither the graphene lattice nor any defects are directly visible, yet a reconstruction algorithm that utilizes maximum likelihood can retrieve effective high dose views of hidden structures.