SURFACE-STRUCTURE AND OXIDATION OF SI(001)-BI

The geometric structure, electronic state and reaction with O2 of the Si(001) surface with Bi overlayer have been studied by LEED, XPS and UPS. Bi(0001) was grown epitaxially with interface structure of Bi(0001){single bond}Si(001) and Bi[2110]{single bond}Si[110] when Bi was deposited on Si(001)2 × 1 clean surface at room temperature. Subsequent annealing to 570-720 K caused the desorption of Bi, and successive phase transition of the 2 × n (10 > n > 5) surface structure was observed around 1 ML (i.e. atomic ratio of Bi to first layer Si is unity). The effect of an O2 exposure of 1000 L at 570-720 K depended upon initial Bi coverage. At submonolayer Bi coverage, O2 exposure induced the oxidation of Si surface and the desorption of Bi. On the other hand, the 2 × n surface which corresponded to about 1 ML were stable against O2, indicating strong interaction between Bi and Si. At higher coverage, excess Bi atoms were oxidized. © 1990 Pergamon Press plc.