Effect of beam energy and surface temperature on the dissociative adsorption of H₂ on Si(001)

Reviews and Highlights	Quantum Science	Molecular and Soft-matter	Ultrafast Nano-optics and Nanophotonics	Mineralogy and Geochemistry

M. Dürr, M.B. Raschke, U. Höfer
The Journal of Chemical Physics 111 (23), 10411-10414
DOI PDF

Dissociative adsorption of H₂ from a high-flux supersonic molecular beam on flat and vicinal Si(001) surfaces was investigated by means of optical second harmonic generation (SHG). The initial sticking coefficients for terrace adsorption varied between 10^-8 and 10^-4. They revealed a strongly activated dissociation process, both with respect to the kinetic energy of the incident molecules (70 meV ≤ E_kin ≤ 380 meV) and the surface temperature (440K ≤ T_s ≤ 670 K). The results indicate that dynamical distortions of Si surface atoms can lower the effective adsorption barriers from 0.8±0.2 eV to almost negligible values. Previously proposed defect-mediated processes can be ruled out as a major adsorption channel.