Electron-Stimulated Desorption of a Br-Chemisorbed Si(111)-7 ×7 Surface by Using a Scanning Tunneling Microscope

Abstract

Atomic structural changes of Br-chemisorbed Si(111) surfaces under electron-stimulated desorption have been investigated by using field-emitted electrons from the tip of a scanning tunneling microscope. Irradiating these surfaces with 30-eV electrons induces various desorptions depending on the initial Br coverage. At low coverage, only Br atoms desorb, and no atomical changes occur on the Si surface. At saturation coverage, Si adatom desorption becomes remarkable but Br atoms more predominantly desorb from the adatom layer. After the irradiation, a novel structure consisting of four Si atoms appears around the dimer position in a 7×7 unit cell. This structure is evidence that the positions of the adatoms are shifted by multiple brominations and these Br atoms are preferentially removed by electron-stimulated desorption.