Adsorption process of chlorine on Si (111)7×7 studied by surface differential reflectivity and second harmonic generation

The adsorption process of chlorine on Si (111)7×7 has been studied by means of real-time surface differential reflectance (SDR) spectroscopy and second harmonic generation. Time evolution of adsorption on adatom dangling bonds and breaking of adatom back bonds are obtained from SDR spectra and second harmonic intensity. The initial sticking probability on the dangling bonds and the initial breaking probability of the back bonds are determined by fitting the time evolution to the solutions of the rate equations for the adsorption of atoms without migration. Temperature dependence of these probabilities reveals that both the adsorption on adatom dangling bonds and breaking of adatom back bonds proceed without potential barriers, and that a metastable state exists in the breaking process of the back bonds.