Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 21, Pages 9496-9501Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0912716107
Keywords
nanoelectronics; single-electron charging; shell structure; electrostatic force microscopy
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Funding
- Natural Sciences and Engineering Research Council of Canada
- le Fonds Quebecois de le Recherche sur la Nature et les Technologies
- Carl Reinhardt Fellowship
- Canadian Institute for Advanced Research
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Strong confinement of charges in few-electron systems such as in atoms, molecules, and quantum dots leads to a spectrum of discrete energy levels often shared by several degenerate states. Because the electronic structure is key to understanding their chemical properties, methods that probe these energy levels in situ are important. We show how electrostatic force detection using atomic force microscopy reveals the electronic structure of individual and coupled self-assembled quantum dots. An electron addition spectrum results from a change in cantilever resonance frequency and dissipation when an electron tunnels on/off a dot. The spectra show clear level degeneracies in isolated quantum dots, supported by the quantitative measurement of predicted temperature-dependent shifts of Coulomb blockade peaks. Scanning the surface shows that several quantum dots may reside on what topographically appears to be just one. Relative coupling strengths can be estimated from these images of grouped coupled dots.
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