The structure and growth process of Au/Si(1 1 1) analyzed by high-resolution ion scattering coupled with photoelectron spectroscopy

We analyzed both the elemental depth profile and chemical bonds of Au/p-Si(1 1 1)-7 × 7 grown at room temperature by medium energy ion scattering combined with photoelectron spectroscopy using synchrotron-radiation-light. It is found unambiguously that Au deposition grows some Au-rich silicide phases for Au coverage above 0.31 ML (1 ML = 0.78 × 1015 atoms/cm2). At an Au coverage of 5.2 ML, the surface comprises a stable Au3Si2 (1.5 × 1015 atoms/cm2: ∼2 atomic layers) layer on top and an underlying metallic Au layer which contains Si atoms diffused in the boundaries of fine Au grains. Indeed, we observed two components for Au 4f (Au–silicide and metallic) and three components for Si 2p spectra (bulk, Au–silicide, and incorporated in an Au layer). Further Au deposition increases thickness of the underlying Au layer without changing the thickness of the Au3Si2 layer on top. Total number of Si atoms consumed to form the Au3Si2 layer and contained in the underlying Au layer coincides with the number of Si atoms making the 7 × 7 reconstruction. The present study reveals clearly the dynamic process happening at the Au/Si(1 1 1) interface.