| Surface science techniques have proven to be extremely useful for studying the molecular level details of gas-surface reactions related to semiconductor device manufacturing and heterogeneous catalysis. In particular, molecular beam techniques are a very accurate way to measure adsorption probabilities as a function of the translational energy, incident angle, and surface temperature. These measurements provide information about the mechanisms of adsorption and details of the potential energy surface. Here, molecular beam techniques are employed to investigate the kinetics and dynamics of adsorption on both semiconductor and metal surfaces.; The physical adsorption probability, or trapping probability, of ethane on Si(100)-(2x1) was experimentally measured at a surface temperature of 65 K. While the translational energy dependence of the trapping probability is consistent with all previous studies of trapping dynamics, the measurements show an angular dependence that has been seen in very few cases. Molecular dynamics simulations were employed to investigate the physical origin of this angular dependence. These simulations show that the angular dependence arises from the exchange of parallel and normal momentum of the molecule by the corrugation of the potential energy surface. These calculations indicate that the initial rotational energy of the molecule does not significantly affect the trapping probability until the rotational state exceeds about J = 20. Also, the calculated trapping probabilities were found to be relatively independent of the surface temperature up to 200 K, but decrease significantly at higher temperatures.; The dissociative adsorption probabilities of chloromethanes on Ir(110) were measured as a function of surface temperature and incident angle. These measurements indicate that adsorption occurs through a trapping-mediated mechanism where the molecule must physically adsorb before dissociatively adsorbing. Accumulation of Cl on the surface decreases the adsorption probability of CCl4 and causes the adsorption probability to become more sensitive to the surface temperature. Pre-adsorption of hydrogen into the β 2 adsorption state was not found to significantly affect the adsorption probability of CCl4 and CHCl3 at low surface temperatures. However, it can block the dissociative adsorption of CH2Cl 2 and CH3Cl. Pre-adsorbed hydrogen was also found to react with dissociatively adsorbed CCl4 and CHCl3 to produce hydrodechlorination products. |
