Role of misfit strain and proximity in epigrowth modes I. Strong epilayer-substrate interaction

Abstract

The objectives of this study are to assess the effects of misfit strain and substrate proximity on the evolution of growth modes — emphasizing the transition to Stranski-Krastanov (SK) growth — during thickening of a growing epilayer. The study comprises a generalization of Bauer's equilibrium criteria and their application to the growth of Cu and Ni on W(110) — a strong interacting substrate — using embedded-atom methods (EAM) calculations. It is suggested that proximity is propagated by epilayer-substrate bond strength and interlayer relaxation, and that the proximity range is strongly influenced by cutoffs which model the limited range of electronic induced atom-atom interaction. The study shows that the contribution of misfit strain energy to shaping growth modes is nonlinear and indeed vanishes outside the proximity range. The predictions are in agreement with the observed Frank-van der Merwe (FM) growth of the first monolayer (ML) and a SK transition thereafter. EAM calculations also confirm the anticipated relative strengths of bonding. Calculated activation energies of surface migration suggest that adatoms are significantly more mobile on top of thin epilayers than on the bare strong interacting substrate and that this will also strongly influence equilibration kinetics.