title: Subatomic Features on the Silicon (111)-(7x7) Surface Observed by Atomic Force Microscopy.
abstract: The atomic force microscope images surfaces by sensing the forces between a sharp tip and a sample. If the tip-sample interaction is dominated by short-range forces due to the formation of covalent bonds, the image of an individual atom should reflect the angular symmetry of the interaction. Here, we report on a distinct substructure in the images of individual adatoms on silicon (111)-(7x7), two crescents with a spherical envelope. The crescents are interpreted as images of two atomic orbitals of the front atom of the tip. Key for the observation of these subatomic features is a force-detection scheme with superior noise performance and enhanced sensitivity to short-range forces.
authors.affiliation: Experimentalphysik VI, Center for Electronic Correlations and Magnetism (EKM), Institute of Physics, University of Augsburg, 86135 Augsburg, Germany.
authors.initials: FJ
authors.lastname: Giessibl
authors.initials: S
authors.lastname: Hembacher
authors.initials: H
authors.lastname: Bielefeldt
authors.initials: J
authors.lastname: Mannhart