Dimer and String Formation during Low Temperature Silicon Deposition on Si(100)

We present theoretical results based on density functional theory and kinetic Monte Carlo simulations of silicon deposition and address observations made in recently reported low temperature scanning tunneling microscopy studies. A mechanism is presented which explains dimer formation on top of the substrate's dimer rows at 160 K and up to room temperature, while between-row dimers and longer strings of adatoms (``diluted dimer rows'') form at higher temperature. A crossover occurs at around room temperature between two different mechanisms for adatom diffusion in our model.