Stability of B and Ga Induced Surface Structures on Si(111) During Deposition and Epitaxial Growth of Si

We have investigated the sqrt (3X) sqrt 3 surface structure of B/Si(111) using in-plane and out-of-plane x-ray data. The in-plane data is unsurprising, showing an adatom and surrounding displacements analogous to Sn/Ge(111) pb/Ge(111) Sn/Si(111) studied previously with x-rays. The Si displacement is 0.35angstroms, somewhat larger than the others. The out-of-plane data shows much more structure than expected and can only be explained by a subsurface B site and Si adatom. This is sensible from bond length arguments and nicely explains dramatic differences seen in the growth behavior of Si on B/Si(111) versus Ga/Si(111).