Structural study of the close-packed two-dimensional phases of Pb on Ge(111) and Si(111).

Abstract

The close-packed two-dimensional structures of Pb on Ge(111) and Si(111) have been studied with scanning tunneling microscopy (STM), reflection high-energy electron diffraction, and low-energy electron diffraction. Several closely-related commensurate and incommensurate phases were observed. For both adsorbate systems, schematic phase diagrams are derived and compared to the predictions of the domain-wall theory for commensurate-incommensurate phase transitions. A complex structural model is presented which describes the various incommensurate phases and is in good agreement with the STM data.