An electron-spin-resonance study has been carried out, both isothermally and isochronically, of the recovery under vacuum annealing from the hydrogen passivated state (symbolized as $\mathrm{H}{P}_b)$ of paramagnetic $P_b$ centers $\left({\mathrm{Si}}_3{\mathrm{\equiv }\mathrm{Si}}^{•}\right)$ at the ${\mathrm{}\left(111\right)\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_2$ interface. Previous work had reported simple exponential decay of $\left[P_b\mathrm{H}\right]$ vs time, taken as key evidence for the process obeying the first-order rate equation $d\left[P_b\mathrm{H}\right]/dt=-k_d\left[P_b\mathrm{H}\right],$ where $k_d{=k}_{\mathrm{do}}\exp (-E_d/\mathrm{kT})$ and $E_d$ the single-valued activation energy. This inference, however, suffered from inadequate data. In contrast, experimental upgrading reveals manifest nonsimple exponential decay, which, within the simple thermal model, reveals the existence of a distinct spread ${\sigma }_{E_d}$ in $E_d.$ Incorporation of Gaussian spread in $E_d$ leads to a consistent generalized simple thermal model, that matches physical insight. The broad range of data enabled unbiased determination of the physical parameters involved, giving $E_d=2.83\mathrm{}\pm 0.02\mathrm{eV},$ ${\sigma }_{E_d}=0.08\mathrm{}\pm 0.03\mathrm{eV},$ and attempt frequency $k_{\mathrm{do}}=(1.6\mathrm{}\pm 0.5)\times {10}^{13}{\mathrm{s}}^{\mathrm{-}1},$ close to the Si-H waging mode frequency, which provides a clue to the atomic dissociation mechanism. The spread ${\sigma }_{E_d}$ results from the interfacial stress-induced variations in $P_b$ defect morphology. The body of data is found incompatible with second-order kinetics, thus exposing $P_b\mathrm{H}$ dissociation as an individual process. Combination with the previous generalized thermal model for $P_b$ passivation with ${\mathrm{H}}_2$ culminates in a consistent unified picture of the $P_b$-hydrogen interaction kinetics.

• Received 5 May 1999

DOI:https://doi.org/10.1103/PhysRevB.61.8393