EFFECTS OF AN ANOMALOUS STRAIN ACCOMMODATING BEHAVIOR OF SI AD-DIMERS ON THE NUCLEATION OF REGULAR AND DEFECT ISLANDS

Computer simulations, based on a theory relating the binding energy Of a Si adatom on the Si(001)-2 x 1 surface to the excess strain and local configuration energy resulting from the presence of the adatom, have been performed to study the nucleation of 1D dimer strings. We found an anomalous strain accommodating behavior of ad-dimers that explains the greater stability of adatoms adsorbed at ad-dimer sites. This behavior also accounts for the occurrence of non-lattice binding sites, which are closely connected to defect formation at low temperatures, in the neighborhood of ad-dimers.