HOMOEPITAXY OF SI(111) IS SURFACE DEFECT-MEDIATED

Superstructure domain boundaries (linear surface defects) act as islan d nucleation sites in steady state Si(111) homoepitaxial growth below 650 degrees C. The dependence of the average island size on the deposi tion rate R allows the estimation of the size of the critical nucleus i to be only one or two atoms. This heterogeneous nucleation mechanis m dominates the multilayer steady state growth regime. This is in cont rast to the homogeneous nucleation of Si in the submonolayer regime on the perfect Si(111)-(7x7) surface, where a critical nucleus size of i greater than or equal to 5 is reported. Scaling of the temperature o f growth and the deposition rate is observed. We do not observe a buil t up of the lateral and vertical surface roughness during growth: ther e is no Schwoebel barrier.