Kinetic and relativistic effects on the surface alloy formation of submonolayer Au adsorbed on Si(111)-[formula]-Pb surface.

Experiment reveals that the two-dimensional ordered phase of 3 × 3-Au/Pb alloy formed on Si(111)-[formula]-Pb surface is dominated by Au parallelogram tetramers (4P). However, theoretical results indicate that three-dimensional tetrahedral tetramers (4T) grown on such surface is more energetically favorable. Using first-principles methods, we show that the discrepancy originates from a lower potential energy barrier of formation of the metastable 4P phase than that of the formation of stable 4T phase in nucleation and subsequent growth processes from triangular trimers (3T) islands and from stronger competition between Au s and d states caused by spin-orbit coupling effects. [ABSTRACT FROM AUTHOR]