Showing papers by "Ondrej L. Krivanek published in 2012"
TL;DR: Using aberrationcorrected scanning transmission electron microscope and energy dispersive x-ray spectroscopy, single, isolated impurity atoms of silicon and platinum in monolayer and multilayer graphene are identified.
Abstract: Using aberration-corrected scanning transmission electron microscope and energy dispersive x-ray spectroscopy, single, isolated impurity atoms of silicon and platinum in monolayer and multilayer graphene are identified. Simultaneously acquired electron energy loss spectra confirm the elemental identification. Contamination difficulties are overcome by employing near-UHV sample conditions. Signal intensities agree within a factor of two with standardless estimates.
80 citations
TL;DR: It is shown that aberration-corrected scanning transmission electron microscopy operating at low accelerating voltages is able to analyze, simultaneously and with single atom resolution and sensitivity, the local atomic configuration, chemical identities, and optical response at point defect sites in monolayer graphene.
Abstract: We show that aberration-corrected scanning transmission electron microscopy operating at low accelerating voltages is able to analyze, simultaneously and with single atom resolution and sensitivity, the local atomic configuration, chemical identities, and optical response at point defect sites in monolayer graphene. Sequential fast-scan annular dark-field (ADF) imaging provides direct visualization of point defect diffusion within the graphene lattice, with all atoms clearly resolved and identified via quantitative image analysis. Summing multiple ADF frames of stationary defects produce images with minimized statistical noise and reduced distortions of atomic positions. Electron energy-loss spectrum imaging of single atoms allows the delocalization of inelastic scattering to be quantified, and full quantum mechanical calculations are able to describe the delocalization effect with good accuracy. These capabilities open new opportunities to probe the defect structure, defect dynamics, and local optical properties in 2D materials with single atom sensitivity.
61 citations
TL;DR: Some four decades were needed to catch up with the vision that Albert Crewe and his group had for the scanning transmission electron microscope in the nineteen sixties and seventies: attaining 0.5Å resolution, and identifying single atoms spectroscopically.
26 citations
18 Dec 2012
20 citations
TL;DR: In this paper, the authors presented an extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 2012.
Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
2 citations
1 citations
01 Jan 2012
TL;DR: Aberration-corrected scanning transmission electron microscopes (STEMs) as mentioned in this paper are versatile instruments that can perform many types of investigations and are equally well suited to performing diffraction studies and combined diffraction+imaging experiments.
Abstract: Aberration-corrected scanning transmission electron microscopes (STEMs) are versatile instruments that can perform many types of investigations. The main use of such microscopes has so far been in direct imaging and analysis, but they are equally well suited to performing diffraction studies and combined diffraction+imaging experiments. The various optical modes needed for such operating modes are reviewed. They include producing electron beams with angular spreads as narrow as a few μrad, and conical precession scans with scan angles >50 mrad.