Spatially resolved manipulation of single electrons in quantum dots   using a scanned probe
  The scanning metallic tip of a scanning force microscope was coupled capacitively to electrons confined in a lithographically defined gate-tunable quantum dot at a temperature of 300 mK. Single electrons were made to hop on or off the dot by moving the tip or by changing the tip bias voltage owing to the Coulomb-blockade effect. Spatial images of conductance resonances map the interaction potential between the tip and individual electronic quantum dot states. Under certain conditions this interaction is found to contain a tip-voltage induced and a tip-voltage independent contribution. 
A. Pioda, S.Kicin, T. Ihn, M. Sigrist, A. Fuhrer, K. Ensslin, A.   Weichselbaum, S. E. Ulloa, M. Reinwald, and W. Wegscheider