Subatomic Features on the Silicon (111)-(7x7) Surface Observed by Atomic Force Microscopy.

Area of Science:

• Surface science
• Atomic force microscopy
• Quantum chemistry

Background:

• Atomic force microscopy (AFM) images surfaces by detecting forces between a tip and sample.
• Tip-sample interactions, especially short-range forces like covalent bonds, influence image formation.
• Understanding atomic-level interactions is crucial for nanoscale imaging.

Purpose of the Study:

• To investigate subatomic features in atomic force microscope images of individual adatoms.
• To analyze the structure of adatoms on silicon (111)-(7x7) surfaces.
• To correlate observed substructures with atomic orbital symmetry.

Main Methods:

• Utilized atomic force microscopy (AFM) with a novel force-detection scheme.
• Achieved superior noise performance and enhanced sensitivity to short-range forces.
• Imaged individual adatoms adsorbed on a silicon (111)-(7x7) surface.

Main Results:

• Observed a distinct substructure within images of individual adatoms.
• This substructure consists of two crescent shapes enclosed by a spherical envelope.
• The crescents are interpreted as imaging two atomic orbitals of the tip's front atom.

Conclusions:

• The observed substructure provides direct visualization of atomic orbital symmetry in AFM.
• This finding demonstrates the capability of advanced AFM force detection to resolve subatomic details.
• The results offer new insights into tip-sample interactions at the atomic scale.