Metastable-atom-stimulated desorption from hydrogen-passivated silicon surfaces

Ion desorption stimulated by a slow metastable helium atom beam is investigated for hydrogen-passivated Si(1 1 1) surfaces using a pulsed discharge metastable-atom source, which also generates photons (He I) and fast neutrals (He0). The time-of-flight spectrum of desorbed positive ions shows peaks corresponding to H+ stimulated by metastable-helium atoms and to ions sputtered by fast neutrals but no peak relevant to the photons. The lack of photon-stimulated desorption excludes the possible contribution of secondary electrons to the metastable-atom-stimulated desorption (MSD). The narrow energy distribution of MSD ions and the metastable atom deexcitation spectroscopy measurement prove that the MSD is induced by electronic transitions initiated by the abstraction of electrons from the valence band of the silicon hydrides during the Auger-type decay of metastable helium atoms.