ISLAND STRUCTURE EVOLUTION DURING CHEMICAL-VAPOR-DEPOSITION

Scanning tunneling microscopy (STM) and Monte Carlo simulations are us ed to investigate the development of island structure during low-press ure, chemical vapor deposition (CVD) of metal onto clean Si(100) subst rates. For Fe growth via Fe(CO)(5) pyrolysis, STM shows that precursor molecules initially decompose at Si dangling bond sites. The nucleati on rate is strongly dependent on substrate temperature with rapid deco mposition al 200 degrees C and zero reaction at room temperature (for exposures as large as 100 L). At later stages STM shows that island st ructure is dominated by differential reaction probabilities. A small b arrier to decomposition on Fe compared with Si leads to large clusters and a nonlinear growth rate. This autocatalytic growth behavior is al so reflected in the measured island size distributions. Kinetic Monte Carlo simulations confirm that chemical reaction kinetics influence Fe film growth, while precursor molecule diffusion does not play a major role in the evolution of island structure. Using simulations, we also demonstrate how CVD film structure can differ from that developed dur ing solid-source molecular beam epitaxy.