Scanning tunneling microscopy evidence of a special bonding of Cu adatoms on Si(111)-√3 x √3-Ag surface -: Direct observation of surface-state electron migration

STM observations provide direct evidence that the S-1 surface states around the Cu adatoms on the root 3 x root 3-Ag substrate are donated by excess electrons from Cu adatoms, resulting in metallic surface bonds of Cu adatoms on the root 3 x root 3-Ag surface. These donated electrons can easily migrate along the SI surface states together with the Cu adatoms: this can be explained by the delocalized character of the S-1 surface state and the Coulomb attraction between the donated electrons and the adatoms. (C) 2000 Elsevier Science B.V. All lights reserved.