Clustering of Charged Adsorbates: Scanning Tunneling Microscopy Observations of Chlorine on Gallium-Rich GaAs(001)-c(8×2)

The forces between adsorbates on metals are often repulsive due to dipole−dipole interactions. Electronegative adsorbates on semiconductors, however, sometimes form clusters, exhibiting attractive interactions even though the same dipole−dipole model should apply. Here we report observations with scanning tunneling microscopy of the clustering of chlorine chemisorbed on the gallium arsenide(001)-c(8×2) surface. For this system, the adsorbate …