Epitaxial orientation changes in a dewetting gold film on Si(111).
Résumé
Using in situ x-ray diffraction, epitaxial relationships have been measured for different Au deposits on Si(111) surfaces, under ultrahigh vacuum conditions, from room temperature to the eutectic temperature (T-e) of theAuSi binary system. Epitaxies perpendicular to the substrate have been studied for different gold coverages (2, 5, 7, and 20 monolayers). The Au(111) parallel to Si(111) out-of-plane epitaxy was found to be dominant and to present three different in-plane orientation relationships evolving with increasing temperature. These epitaxial variations are induced by the variation of the lattice-parameter misfit with temperature due to differing thermal expansion of the two materials. The temperature dependence of the epitaxial relationship is explained using the coincidence site lattice theory and a study of the "matching quality" at the interface. In addition, ab initio calculations have been performed to estimate the stability of the different configurations and compared to the experimental results