VUV photodesorption of molecular hydrogen from the hydrogenated silicon(111) surface

The photochemical desorption of molecular hydrogen was investigated by F2-laser irradiation (157 nm) of a Si(111)–(1×1):H surface. The photon energy of 7.9 eV used was in the region of the broad σ–σ* optical transition of SiH centered around 8.5 eV. Molecular-dynamics calculations, based on a Tersoff-type interaction potential between silicon and hydrogen, describe the reaction of a hydrogen atom created in a direct bond-breaking process with a neighboring hydrogen atom to form molecular hydrogen. This secondary surface reaction preserves the non-thermal character of the desorption process.