Hydrogen interactions with cavities in helium-implanted germanium

The interactions of hydrogen with cavities in Ge were investigated and used to determine the binding energy of H at the Ge surface. Cavities were formed by He ion implantation and annealing, and their microstructure was characterized by transmission-electron microscopy. Hydrogen was then introduced by ion implantation, and during subsequent heating the bonding and eventual release of the H were monitored using Fourier-transform infrared spectroscopy and nuclear-reaction analysis. Analysis of the resulting data yielded a dissociation energy of 1.9±{}0.2 eV for the Ge-H surface-monohydride bond. This implies that H₂ gas, with a binding energy of 2.26 eV per atom, is energetically preferred to the adsorbed state on Ge, in contrast to the situation for the Si surface.