Self-assembled gold silicide wires on bromine-passivated Si(110) surfaces

Thin Au films (similar to 45 nm) deposited by thermal evaporation under hig h vacuum on bromine-passivated Si(110) substrates, upon annealing showed th e formation of long gold silicide wire-like islands on top of a thin unifor m layer of gold silicide in a self-assembled Stranski-Krastanov growth proc ess. Optical micrographs showed long, straight and narrow islands with aspe ct ratios as large as 200:1. Scanning electron microscopy images revealed t he presence of facets. The islands are aligned along the [(1) over bar 10] direction on the Si(110) surface. Rutherford backscattering spectrometry me asurements with an ion microbeam identified the islands to possess varying thickness across a single island as one would expect for islands having fac ets and also showed the uniform silicide layer over the Si substrate to be very thin (similar to 1.5 nm). The observed alignment of the gold silicide islands on the Si(110) surface has been explained in terms of the lattice m ismatch between gold-silicide and silicon and invoking the theory of shape transition in heteroepitaxial growth. We have observed islands as long as 2 00 mu m and as narrow as 100 nm in this nonultlahigh vacuum growth on chemi cally passivated Si(110) surfaces. The method, with properly optimized para meters, may provide a way to grow quantum wires. (C) 2000 American Vacuum S ociety. [S0734-211X(00)04404-8].