Adsorption of Ba on Si(001)2 x 1 surface

The initial adsorption of Ba on the Si(001)2 x I surface at 870 degrees C h as been studied by low-energy electron diffraction (LEED), X-ray photoelect ron spectroscopy (XPS), and angle-integrated ultraviolet photoelectron spec troscopy (AIUPS). The valence band, Si and Ba core level spectra and the wo rk-function change (Delta phi) were measured. The double domain (DD) (2 x 3 )-, DD c(2 x 6)- and DD (2 x 1)-Ba surfaces appeared depending on the Ba co verage. AIUPS results show that both DD (2 x 3)-Ba and DD (2 x 1)-Ba surfac es ale semiconducting in nature. The intensity ratio data of XPS core level s (Ba 3d/Si 2p) and the work-function change data reveal that the Ba covera ges of the (2 x 3)-Ba and the DD (2 x I)-Ba surfaces are 1/3 ML and 1/2 ML, respectively. The AIUPS spectra show that the structural models with Ba co verage of 1/3 ML and 1/2 ML, at the bridge sites between two Si dimers are reasonable for the (2 x 3)-Ba and the (2 x 1)-Ba surfaces, respectively.