Soft incommensurate reconstruction on Pb/Si(111): Structure, stress modulation, and phase transition

We resolve the atomic structure of the one-monolayer incommensurate (IC) reconstruction of Pb on Si(111) using a tunneling microscope. The local structure of this surface consists of two types of Pb trimers and a quasi-1×{}1 region, while on larger (>10 {}) scales the trimers are assembled into alternating domains discommensurate with the substrate. One feature of this surface is the sensitivity of the domain morphology to surface-stress inhomogeneities. This sensitivity dramatically alters the temperature at which the IC phase transforms locally to a 1×{}1 phase.