Influence of steps and defects on the dissociative adsorption of molecular hydrogen on silicon surfaces
The dissociative adsorption of molecular hydrogen on vicinal Si(001) and Si(111) surfaces was investigated by means of optical second-harmonic generation (SHG). For temperatures up to 600 K the measured initial sticking coefficients could be decomposed into contributions from step/defect and terrace sites. Whereas the presence of steps on Si(111) leads only to a moderate increase of reactivity, the sticking coefficients for step adsorption on misoriented Si(001) are many orders of magnitude higher than for terrace adsorption and reach values up to 10-4. Neither the absolute values nor the temperature dependence of adsorption on the terraces are affected by the misorientation.