Hydrogen surface segregation on Si(111) by photon-stimulated desorption at the Si K edge

The photon-stimulated desorption of H+ from cleaved Si(111) using photon energies near the Si K excitation threshold is reported. The time dependence of the H surface segregation from the bulk following cleavage shows two or three sequential time regimes of growth kinetics suggesting multiple sequential hydride phase formations. Removal of the H from the H-saturated surface results in the subsequent observation of only the first time regime (which we interpret as being due to formation of a monohydride phase).