Fabrication of an Artificial Aromatic Molecule Constructed from Silicon Dangling Bonds and Measurement of its Molecular Orbitals Using Scanning Tunneling Microscopy and Spectroscopy

Hydrogen atoms that terminate a silicon (100) surface can be selectively removed with atomic-precision by means of feedback controlled lithography with a scanning tunneling microscope tip. Atomic sites on the silicon surface that have been stripped of their hydrogen atoms present a dangling bond above the bare silicon atom that remains. Studies on linear chains of dangling bonds have led to and provided preliminary evidence for the hypothesis that dangling bonds on the Si (100) surface can be thought of as artificial atoms that, when arranged together in an appropriate manor, will form molecular analogues. For the first time, we demonstrate a 2-dimensional arrangement of dangling bonds that forms an artificial silicon-based aromatic molecule surrounded by a hydrogen terminated surface. This is confirmed by scanning tunneling spectroscopy measurements of the resulting molecular orbitals which are found to be in good agreement with those predicted by density functional theory calculations.