Photochemical Hydrogen Desorption from H-Terminated Silicon(111) by VUV Photons

The 7.9 eV photons of a F₂ laser induced photochemical desorption of molecular hydrogen from Si(111)-(1×1):H surfaces with a cross section of (1.2±0.8)×10^-20cm². The time-of-flight detection of desorbing species and numerical calculations of surface heating clearly allowed photochemical F₂-laser (7.9 eV) desorption and photothermal XeCl-laser (4.0 eV) desorption to be distinguished. Molecular dynamics simulations indicate the appearance of atomic and molecular hydrogen. The efficiency of photodissociation and desorption is higher than for the electron-stimulated process.