Monte Carlo simulations of Si(001) growth and reconstruction during molecular beam epitaxy

A Monte Carlo simulation of Si(001) crystal growth and surface reconstruction during molecular beam epitaxy is described. The simulation is based on the solid-on-solid model and depicts the diamond lattice and surface reconstructions explicitly. Si deposition, surface diffusion, and the formation and reorientation of surface dimer pairs are accounted for. The results indicate that surface dimer formation plays an important role in determining the crystal growth kinetics, which is observed to be a combination of step propagation and two-dimensional island nucleation modes. At least 5 diffusion events per deposited atom and second nearest neighbor interaction energies E₂ ≳ kT were required to yield films with mean-square surface roughnesses of ≲ 0.7 monolayer. Decreasing either the diffusion rate or E₂ yielded increasingly rough surfaces. Ordered (2 × 1) rows of dimer pairs were observed when a term accounting for the subsurface strain energy interaction between dimers was included. First-order reflected electron intensity calculations for the simulated surfaces showed strong intensity oscillations with a period of 1 monolayer.