The influence of boron on Si molecular beam epitaxy was investigated as function of coverage and temperature by reflection high-energy electron diffraction (RHEED). The development of the boron-covered Si surface was studied additionally by ultraviolet photo electron spectroscopy (UPS) as function of boron coverage (cB) and annealing condition. A direct correlation was found between the appearance of surface states in UPS and the transient growth behaviour observed in RHEED. For cB>0.4 monolayer (ML) regular RHEED oscillations occurred with a period typically for two bilayers (BLs), whereas for lower cB a transient behaviour with irregular intensity oscillations was observed in the initial growth stages. The appearance of this transient behaviour was discussed in terms of an initial surface defect-induced nucleation of BL-high Si islands and the formation of two BLs-high Si islands on top of the van der Waals-like perfect boron-covered surface, respectively. The occurrence of surface defects for cB<0.6ML was clearly established in UPS measurements, where an intensity peak slightly below the Fermi level (-0.4eV) was visible. It was suggested that this surface defect level was related to Si adatom dangling bonds acting also as preferential nucleation centres in epitaxy. Furthermore, surface defects results in a significant Fermi level pinning.

Role of Boron and (√3 x √3)-B Surface Defects on the Growth Mode of Si on Si(111) - a Photoemission and Electron Diffraction Study. A.Fissel, J.Krügener, D.Schwendt, H.J.Osten: Physica Status Solidi A, 2010, 207[2], 245-53