Limits of elemental contrast by low energy electron point source holography

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Journal titleJournal of Applied Physics
Article number94305
SubjectBiological molecule; Chemical information; Coherent sources; Elastic scattering cross sections; First order; In-line holography; Low energy electrons; Model results; Phase contrasts; Point projection; Point sources; Scattering factors; Single atoms; Small damage; Small molecules; Atoms; Balloons; Graphene; Holography; Nanostructures; Rutherford backscattering spectroscopy; Electrons
AbstractMotivated by the need for less destructive imaging of nanostructures, we pursue point-source in-line holography (also known as point projection microscopy, or PPM) with very low energy electrons (∼100 eV). This technique exploits the recent creation of ultrasharp and robust nanotips, which can field emit electrons from a single atom at their apex, thus creating a path to an extremely coherent source of electrons for holography. Our method has the potential to achieve atom resolved images of nanostructures including biological molecules. We demonstrate a further advantage of PPM emerging from the fact that the very low energy electrons employed experience a large elastic scattering cross section relative to many-kV electrons. Moreover, the variation of scattering factors as a function of atom type allows for enhanced elemental contrast. The idea that one can obtain chemical information about a sample whereas imaging it by PPM is worth pursuing in more detail, and here we undertake simulations of this scheme to assess its feasibility to first order. Model results for small molecules and adatoms on graphene substrates, where very small damage is expected, indicate that a phase contrast is obtainable between elements with significantly different Z-numbers. For example, for typical setup parameters, atoms such as C and P are discernible, whereas C and N are not. © 2011 American Institute of Physics.
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AffiliationNational Research Council Canada (NRC-CNRC); National Institute for Nanotechnology (NINT-INNT)
Peer reviewedYes
NPARC number21271444
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Record identifierd148a5d5-cc0c-45f9-a693-2aa5d3c7aacd
Record created2014-03-24
Record modified2016-05-09
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