Nucleation on Defects in Heteroepitaxy

The rate equation treatment of nucleation and growth on perfect substrates has been extended to cover nucleation on random defect sites, and problems involving 1-dimensional (1D) diffusion to sinks. This paper recaps the results of rate equation treatments on perfect terraces, and sumnarises some new models, including: 1) nucleation on point defects, with application to nm-sized Fe and Co particles grown on various CaF2substrates; 2) nucleation and diffusion in finite 1D deposits, with application to diffusion over, and the break-up of, multilayer deposits of Ag/Ge(111) and Ag/Fe(110); 3) 1D models developed for nucleation in competition with step capture. Comparison of rate-diffusion equations with experiment can result in values for, or bounds on, the controlling energies, in a way which illuminates the main features of interatomic forces at surfaces. The use of defects to grow thin film arrays for practical application presents some interesting challenges at both the nucleation and growth stages, which are discussed briefly.