Surface reconstructions in Pb/Si(100) system: Composition and atomic arrangement

Abstract

Using scanning tunneling microscopy and density functional theory calculations, atomic arrangement of surface reconstructions in Pb/Si(100) system was examined. Through accurate evaluation of Pb coverage, it was determined that 2 × 2 reconstruction contains 0.5 monolayer (ML) of Pb, c(8 × 4) - 0.75 ML of Pb, 2 × 1 - 1.5 ML of Pb, and c(4 × 4) - 1.875 (15/8) ML of Pb. It was revealed that the 2 × 2-Pb reconstruction can occur in two possible modifications, with buckled Pb dimers in the trenches between Si-dimer rows and with symmetric Pb dimers atop Si-dimer rows. The 2 × 2-Pb reconstruction of the latter type develops mainly on the Si(100)2 × 1 surface which contains relatively large density of structural defects. Known structural models of the c(8 × 4) and 2 × 1 reconstructions were tested and received the confirmation. A new model was proposed for the c(4 × 4) structure. The obtained data set is believed to constitute a solid base for the prospective studies of the phenomena occurring in the Pb/Si(100) system. In particular, the Pb-dense reconstructions, 2 × 1 and c(4 × 4), might be plausible candidates for detecting superconducting properties by analogy with the Pb-dense reconstructions on Si(111).