IDENTIFICATION OF ORDERED ATOMIC STRUCTURES OF BA ON THE SI(100) SURFACE

Three long-range ordered atomic structures of (2 X 3), (1 X 2) and (2 X 4) phases have been observed by low-energy electron-diffraction (LEED) in the Ba/Si(100) surface at submonolayer Ba coverages (theta < 1 ML). The relationship between the observed phases for Ba on the Si(100) surface have been described as a function of Ba coverage and anneal temperature. Possible models of the surface atomic structures for the ordered phases are proposed by assuming Ba atomic chains in the Ba overlayer. A diffuse c(4 X 4)-like pattern has also been observed in the Ba/Si(100) system at high Ba exposure (> 2 ML), which might result from Ba diffusion and possible formation of a barium silicide.