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

The 7.9 eV photons of a ${\mathrm{F}}_2$ laser induced photochemical desorption of molecular hydrogen from $\mathrm{Si}\left(111\right)-(1\times 1):\mathrm{H}$ surfaces with a cross section of $(1.2\pm 0.8)\times {10}^{-20\mathrm{}}\mathrm{cm}{}^2$. The time-of-flight detection of desorbing species and numerical calculations of surface heating clearly allowed photochemical ${\mathrm{F}}_2-\mathrm{laser}$ (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.