EPITAXY AND DOMAIN GROWTH OF PB ON NI(001)

We study the growth of the c(2 x 2) structure of Pb on Ni(001) with high-resolution x-ray diffraction. By monitoring the adsorbate-substrate and the adsorbate-adsorbate interference diffraction peaks, we are able to determine the registry and growth process of the first overlayer. Pb atoms change from hollow site to non-hollow site growth as coverage increases. Results at higher substrate temperatures indicate a different growth process at low coverage. We propose a model of adsorbate aggregation at sites in line with Ni atoms around pinning centres to account for the observed results.