Cryogenic UHV-STM Study of Hydrogen and Deuterium Desorption from Si(100)

A cryogenic UHV scanning tunneling microscope has been used to study the electron stimulated desorption of hydrogen and deuterium from Si(100) surfaces at 11 K. A strong isotope effect is observed, as seen previously at room temperature. Above ∼5 eV, the desorption yields for H and D are temperature independent, while in the tunneling regime, below 4 eV, H is a factor of ∼300 easier to desorb at 11 than at 300 K. This large temperature dependence is explained by a model that involves multiple vibrational excitation and takes into account the increase of the Si-H(D) vibrational lifetime at low temperature.