Presented by Jinho An, University of Texas
Discovery of the unique physical properties of graphene, and its potential for vast engineering applications has drawn significant interest of the science community for the past 6 years. While there have been significant advances made in understanding the physical properties of graphene, the difficulty of analyzing mono-atomic thin graphene platelets have prohibited researchers from fully understanding the inherent physical properties of natural (cleaved) and lab-grown graphene, as well as fully analyzing graphene platelets that have been fabricated through chemical methods. While Transmission Electron Microscopy (TEM) has been instrumental in uncovering the structure and properties of various nanoscale materials, the discovery of this novel mono-atomic material has posed new challenges for TEM characterization. While TEM may not be a ‘cure all’ for all analyses, TEM continues to be a valuable tool for investigating graphene, especially through the use of Cs corrected TEMs. In this work, various TEM characterization of graphene and graphene based materials are covered, including classical methods such as SAED (Selected Area Electron Diffraction) and DF (Dark Field) imaging, to the use of state-of-the-art Cs corrected TEM imaging and novel techniques such as ‘D-STEM’ (nanoprobe diffraction analysis in Scanning Transmission Electron Microscope mode). Topics of the talk include the study of domain sizes and domain boundaries in CVD grown monolayer graphene and boundary characteristics, in-situ observations of KCl on graphene and the study of other graphene metamaterials, and the use of TEM for studying the cross section of graphene oxide based paper-like filtered materials. In addition to TEM analysis of graphene itself, the use of graphene as TEM substrates or possibly environmental cell windows may provide for the design of novel TEM experiments, such as in-situ heating/cooling of nanoparticles/clusters and conducting experiments in a gaseous or wet environment.