S. J. Pennycook1,2,3, W. Zhou2,1, J. Lee1,2, J. C. Idrobo1,2, M. P. Oxley2,1, M. Kapetanakis2,1
and S. T. Pantelides2,1
1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6071, USA
2Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
3Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
The aberration-corrected scanning transmission electron microscope (STEM) now allows direct, real space imaging at atomic resolution and low accelerating voltages [1]. In monolayer materials such as BN and graphene, atom-by-atom characterization of atomic position, atomic species and optical and electronic properties has become a practical reality [2]. Stable point defect complexes consisting of substitutional Si and N atoms lead to localized surface plasmon resonances at the sub-nanometer scale, acting as atomic antennae in the petaHertz (1015 Hz) frequency range [3]. Core loss spectroscopy is able to identify the nature of the bonding of single point defects, confirmed by density functional theory. Atomic resolution imaging of valence excitations will also be shown. Finally, the use of the STEM probe to excite the dynamics of small clusters will be illustrated with a Si6 magic cluster embedded in a small hole in monolayer graphene. Movies in the microscope reveal the metastable configurations of the cluster and density functional calculations reveal the energy landscape. These results suggest a new way to explore atomic scale dynamics in small clusters.
[1] S.J. Pennycook, in Scanning Transmission Electron Microscopy, eds. S. J. Pennycook and P. D. Nellist, Springer, pp 1-90, 2011.
[2] O.L. Krivanek, M.F. Chisholm, V. Nicolosi, T.J. Pennycook, G.J. Corbin, N. Dellby, M.F. Murfitt, C.S. Own, Z.S. Szilagyi, M.P. Oxley, S.T. Pantelides, S.J. Pennycook, Nature, 464, 571-574, 2010.
[3] W. Zhou, J. Lee, J. Nanda, S. T. Pantelides, S. J. Pennycook and J-C. Idrobo, Nature Nanotechnology, 7, 161-165, 2012.
Research supported by the U.S. Department of Energy (DOE), Basic Energy Sciences (BES), Materials Sciences and Engineering Division (S.J.P., J.L., S.T.P.), by ORNL’s Shared Research Equipment (ShaRE) User Program, which is also sponsored by DOE-BES (J-C.I.), by the National Science Foundation (grant no. DMR-0938330; W.Z., J-C.I.), by DOE grant DE-FG02- 09ER46554 (M.P.O., M.K, S.T.P.) and by the McMinn Endowment (S.T.P.) at Vanderbilt University.