Electrochemical growth of gold on well-defined vicinal H-Si(1 1 1) surfaces studied by AFM and XRD

The possibility of preparing structurally well-defined and periodically arranged metal islands on a semiconductor is very attractive for optical and magnetic applications. In this work we used electrochemical deposition to grow nm-sized gold islands that decorate steps on defect-free vicinal H terminated Si(1 1 1) surfaces prepared by chemical etching. The gold deposits were studied by atomic force microscopy and X-ray diffraction. Results show that gold nucleates exclusively along the steps and that the density of nuclei is controlled by the electrode potential. Nearly prefect replication of the periodic array of straight monatomic steps is achieved at sufficiently negative potential. XRD indicates that the structure of gold films evolves from powder-like, close to the onset potential of nucleation (-1.6 V), to strongly epitaxial with the (1 1 1) orientation at more negative potentials. A reaction model and a growth mechanism are proposed to account for the origin of the selective nucleation and the excellent epitaxy obtained. In particular they discuss whether or not the H-monolayer remains intact under the deposit.