LOW-ENERGY ELECTRON-DIFFRACTION AND SCANNING-TUNNELING-MICROSCOPY STUDIES OF THE PT/SI(001) SURFACE

The Pt/Si(001) surface has been investigated by use of low-energy electron diffraction (LEED), Auger-electron spectroscopy, and electron-energy-loss spectroscopy for various Pt coverages and annealing temperatures. A surface phase diagram is formed for Pt coverages less than one monolayer (ML) and annealing temperatures of 20-1100-degrees-C. A mixed LEED pattern of Pt/Si(001) c (4 X 2) and Pt/Si(001) c (4 X 6) of a reconstructed phase has been found at approximately 1/6 to 1/3 ML and annealing temperatures of 550-1050-degrees-C. The surface structure of the reconstructed phase has been analyzed by scanning tunneling microscopy and it is found that the c (4 X 2) reconstruction is formed by the regular arrangement of Pt atoms embedded in fourfold hollow sites surrounded by two dimers and the c (4 X 6) reconstruction is formed by long-range ordering of missing dimer defects superimposed on the c (4 X 2) reconstruction.