Structure Ordering at the Si(111) Surface

Abstract

On the basis of results of surface structure analyses by reflection high—energy electron diffraction (RHEED), we discuss that reconstruction of stacking faults of 7×7 structure into the normal stacking proceeds by homoepitaxial growth or adsorption of extra atoms on the Si(111) surface. During RHEED intensity oscillation with the homoepitaxial growth, a mixed phase of 5×5 and 7×7 structures is observed. This mixed structure at substrate temperatures higher than about 400 ° C is determined as the dimer-adatom-stacking-fault structure by RHEED intensity rocking curve analysis. At about 300 ° C, however, it is found by rocking curve analysis that new 5×5 and/or 7×7 structures with pyramidal clusters are formed on the dimer-stacking-fault (DSF) framework. It is suggested that the formation of such metastable structure promotes successive epitaxial growth accompanied by stacking fault dissolution at the DSF framework. Formation of $\sqrt 3 \times \sqrt 3$ structures on Si(111) by adsorption of metal atoms is also discussed based upon the results of the formation of the metastable structure. We also discuss the order of the phase transition from 7×7 to ”1×1”, the energy difference between T₄ and H₃ sites, and bonding processes during adsorption of atoms.