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

Abstract

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