The mobilities of individual adatoms, and of various structural elements of the O/Cu system, were analyzed on the basis of scanning tunnelling microscopic data. A value of about 10-14cm2/s was estimated for the self-diffusivity of Cu on the base (110) surface at 300K. This was deduced from the motion of steps. The supply of Cu adatoms by evaporation from steps, rather than the migration of individual O or C adatoms on the terraces, was the rate-limiting process in the so-called added-row reconstruction process. This led to a slowing of the transformation with increasing conversion. The kinetics of the 1 x 1 to 2 x 1 reconstruction exhibited that behavior, and supported the operation of a supply-controlled (rather than growth-controlled) mechanism for 2 x 1 formation. Lateral interactions between neighboring -Cu-O-Cu- strings, and lateral displacements of such strings, were considered with regard to the stabilization and growth of 2 x 1 islands and the removal of antiphase domain boundaries. Conversion to the higher-coverage c(6 x 2)O phase was associated with a change in the uppermost-layer Cu density, and with mass transport. Unlike (2 x 1)O formation, this occurred in the immediate vicinity of the activated process site and could be described as being a local solid-solid transformation.

J.Wintterlin, R.Schuster, D.J.Coulman, G.Ertl, R.J.Behm: Journal of Vacuum Science and Technology B, 1991, 9[2], 902-8