First-order isothermal desorption kinetics of chlorine on SiH₂Cl₂-adsorbed Si(100) surface

The isothermal desorption kinetics of chlorine on Si(100) was investigated by observing the chloride coverage on the surface with ultraviolet photoelectron spectroscopy. The samples for desorption were prepared by dichlorosilane adsorption at 600°C under 1 × 10^-6 Torr. We found that the decrease of the chloride coverage showed an exponential dependence on the isothermal annealing time, indicating clearly that the chlorine desorption was a first-order reaction. From the Arrhenius plot of the first-order reaction coefficient, the activation energy of chlorine desorption was obtained to be 48.1 kcal/mol. Furthermore, we clarified by quadrupole mass spectroscopy that the dominant desorption species was the diatomic SiCl molecule. To interpret all these results, we proposed a chlorine desorption reaction model based on the collision between a chloride and a migrating Si adatom released from an atomic step.