Electrochemical Au deposition on stepped Si(111)-H surfaces: 3D versus 2D growth studied by AFM and X-ray diffraction

In order to grow magnetic layers on silicon substrates, a non-magnetic buffer layer is often needed to avoid silicide formation and to reproduce the perpendicular magnetic anisotropy obtained on metal single crystals, as in the case of Co on Au(111) and Pt(111). In this context, we have studied the electrochemical growth of Au buffer layers, and show that it is possible to obtain different film morphologies on hydrogen-terminated vicinal Si(111) surfaces by varying the electrochemical deposition parameters and solution composition. Two different morphologies have been obtained as observed by atomic force microscopy: continuous 2D Au films (chloride solution at pH 4), and films consisting in flat top 3D Au islands decorating the Si(111) step edges (cyanide solution at pH 14). X-ray diffraction measurements reveal that the gold layer and islands have Au(111) orientation and are in epitaxy with the Si(111) surface. In the case of islands, the lateral facets have also Au(111) orientation. Results are discussed within a model in which the breaking of the Si–H surface bonds plays a major role in the Au nucleation and growth mechanisms.