Abstract
The growth of Ge on Ag:Si(111)-√3×√3-R30° has been studied by low-energy electron microscopy (LEEM), low-energy electron diffraction (LEED) and x-ray photoemission electron microscopy (XPEEM). For submonolayer adsorption of Ag at 550°C, the Ag terminated √3×√3-R30° domains decorate the step edges of the substrate. The wetting layer growth and Ge island nucleation on such a step-edge decorated surface is quite similar to Ge growth on bare Si(111)-7×7. During Ge deposition, the √3×√3-R30° domains dissolve and small Ag terminated 3×1 domains are formed that are distributed over the whole surface. Larger 3×1 domains are found only at the circumference of the three-dimensional (3D) Ge islands. From the Ge 3D island morphology, size distribution and density it is concluded that in this submonolayer Ag pre-adsorption scenario there is only little influence of the Ag on the growth kinetics and island geometry. This is completely different for Ge growth on an entirely covered Ag:Si(111)√3×√3-R30° surface. As compared to growth on bare Si(111)-7×7, a strong increase of the diffusion length is observed that leads to a drastic reduction of the island density. Also the island morphology is strongly affected by Ag pre-adsorption in this regime. Instead of triangular islands, we observe huge, irregularly shaped islands that rather resemble a discontinuous Ge film. [DOI: 10.1380/ejssnt.2010.221]
