Formation of an ordered Si dimer structure on HfB2(0001) -: art. no. 155416

An ordered surface structure formed after exposure of the HfB2(0001) surface at 800 degreesC to SiH4(g) followed by annealing at 900 degreesC has been characterized experimentally with low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy (XPS). The structure is described by a (root7xroot3) lattice with a bonded pair of Si atoms in each overlayer unit cell. An absolute Si coverage estimate of 0.48 monolayer based on XPS also supports this structure. Calculations using psuedopotentials within the framework of density functional theory and a five-layer slab model of the substrate show that the threefold hollow site is energetically favored for isolated Si atoms and that Si atoms at next-nearest-neighbor three fold hollow sites will form dimers with a Si-Si distance of approximate to2.4 Angstrom.