Featured Research
from universities, journals, and other organizations
Moving silicon atoms in graphene with atomic precision
Date:
September 12, 2014
Source:
University of Vienna
Summary:
In recent years, it has
become possible to see directly individual atoms using electron
microscopy -- especially in graphene, the one-atom-thick sheet of
carbon. Scientists have now shown how an electron beam can move silicon
atoms through the graphene lattice without causing damage. The research
combines advanced electron microscopy with demanding computer
simulations.
Due to its larger size, a silicon dopant sticks out of the graphene plane.
Credit: Toma Susi, University of Vienna
Richard
Feynman famously posed the question in 1959: is it possible to see and
manipulate individual atoms in materials? For a time his vision seemed
more science fiction than science, but starting with groundbreaking
experiments in the late 1980s and more recent developments in electron
microscopy instrumentation it has become scientific reality. However,
damage caused by the electron beam is often an issue in such
experiments.
The present study focused on single-layer graphene with silicon atoms
embedded into the lattice, previously created and studied by the
collaborators from Manchester and Daresbury in the UK. Due to the larger
size of silicon compared to carbon, these dopant atoms protrude out
from the plane, which makes for interesting dynamics under the electron
beam. The detailed simulations performed at the University of Vienna
showed that the 60 kiloelectronvolt electrons that the cutting-edge Nion
microscopes of both teams use for imaging the structure are not
energetic enough to likely cause the outright ejection of atoms, in line
with what had been observed.
Crucially, however, carbon atoms next to a silicon dopant are slightly less strongly bound, and can receive just enough of a kick to so that they almost escape from the lattice, but are recaptured due to an attractive interaction with the silicon atom. Meanwhile, the silicon relaxes into to the lattice position left empty by the impacted carbon atom, which thus lands back into the lattice on the opposite side from where it started. In effect, the silicon-carbon bond is inverted, which was directly seen by the microscopy teams. Analysing the experimental data of nearly 40 such jumps gave a probability that could be directly compared to the simulations, with remarkable agreement.
Besides being beautiful physics, the findings open promising possibilities for atomic-scale engineering: "What makes our results truly intriguing is that the bond flip is directional -- the silicon moves to take the place of the carbon atom that was hit by a probe electron," explains lead author Toma Susi, physicist and FWF Lise Meitner Fellow at the University of Vienna. "This means that it should be possible to control the movement of one or more silicon atoms in the lattice with atomic precision. So perhaps we'll see a new kind of quantum corral or an university logo made of silicon atoms in graphene in the near future," he concludes.
Crucially, however, carbon atoms next to a silicon dopant are slightly less strongly bound, and can receive just enough of a kick to so that they almost escape from the lattice, but are recaptured due to an attractive interaction with the silicon atom. Meanwhile, the silicon relaxes into to the lattice position left empty by the impacted carbon atom, which thus lands back into the lattice on the opposite side from where it started. In effect, the silicon-carbon bond is inverted, which was directly seen by the microscopy teams. Analysing the experimental data of nearly 40 such jumps gave a probability that could be directly compared to the simulations, with remarkable agreement.
Besides being beautiful physics, the findings open promising possibilities for atomic-scale engineering: "What makes our results truly intriguing is that the bond flip is directional -- the silicon moves to take the place of the carbon atom that was hit by a probe electron," explains lead author Toma Susi, physicist and FWF Lise Meitner Fellow at the University of Vienna. "This means that it should be possible to control the movement of one or more silicon atoms in the lattice with atomic precision. So perhaps we'll see a new kind of quantum corral or an university logo made of silicon atoms in graphene in the near future," he concludes.
Story Source:
The above story is based on materials provided by University of Vienna. Note: Materials may be edited for content and length.
The above story is based on materials provided by University of Vienna. Note: Materials may be edited for content and length.
Journal Reference:
- Toma Susi, Jani Kotakoski, Demie Kepaptsoglou, Clemens Mangler, Tracy C. Lovejoy, Ondrej L. Krivanek, Recep Zan, Ursel Bangert, Paola Ayala, Jannik C. Meyer, Quentin Ramasse. Silicon–Carbon Bond Inversions Driven by 60-keV Electrons in Graphene. Physical Review Letters, 2014; 113 (11) DOI: 10.1103/PhysRevLett.113.115501
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