Island structure evolution during chemical vapor deposition

Scanning tunneling microscopy (STM) and Monte Carlo simulations are used to investigate the development of island structure during low-pressure, chemical vapor deposition (CVD) of metal onto clean Si(100) substrates. For Fe growth via Fe(CO)(5) pyrolysis, STM shows that precursor molecules initially decompose at Si dangling bond sites. The nucleation rate is strongly dependent on substrate temperature with rapid decomposition al 200 degrees C and zero reaction at room temperature (for exposures as large as 100 L). At later stages STM shows that island structure is dominated by differential reaction probabilities. A small barrier to decomposition on Fe compared with Si leads to large clusters and a nonlinear growth rate. This autocatalytic growth behavior is also 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 during solid-source molecular beam epitaxy.