Hydrogen cracking in SiO2: Kinetics for ha dissociation at silicon dangling bonds

The passivation of silicon dangling bond defects by H-2 is an important rea ction in Si/SiO2 devices. The dangling bonds studied in this work are those in the a-SiO2 layers, prototype E' centers. Experimental estimates of the activation energy of this process are 0.3-0.4 eV, but theoretical calculati ons give energy barriers that are much larger, around 0.7-0.8 eV. It was su ggested that the lack of tunneling in the energy barrier calculations is re sponsible for the overestimation. This paper is a systematic examination of this reaction, which includes tunneling corrections using the direct dynam ics variational transition state theory. The inclusion of this effect is sh own to provide an Arrhenius activation energy in good accord with the exper imental values.