Laser-stimulated desorption of H+ from the hydrogenated Si(100) surface

Desorption of H+ ions from hydrogenated Si(100) surface is observed under the irradiation of a low-fluence 193-nm pulsed laser beam. The time-of-flight (TOF) spectra of H+ ions on the monohydride and dihydride surfaces show little differences, both consisting of two peaks, corresponding to mean kinetic energies of 0.09+/-0.05 and 0.38+/-0.06 eV. The substrate temperature dependence of the TOF spectra was studied. It was found that the ratio of the 0.38-eV peak to the 0.09-eV peak increased with the substrate temperature. The experimental results are interpreted using the hydrogen pairing model on Si(100). The 0.09-eV peak and 0.38-eV peak are assumed to correspond, respectively, to the H+ ions desorbing from doubly occupied and singly occupied dimers. The difference of 0.29+/-0.011 eV in the kinetic energies of these two groups of H+ ions is compared with the pairing energy on the H/Si(100) surface. Correction to the kinetic energy of H+ ions due to the image interaction is discussed. From the kinetic energy of the H+ ions, the hole-hole repulsion energy in the Si-H bond is estimated to be 9.4 eV, in agreement with earlier experimental results.