STM induced hydrogen desorption on Si(100)-H(2x1)

With an STM tip it is possible to remove single hydrogen atoms from a hydrogen passivated surface. This is the
ultimate limit in a lithographic process, and opens new possibilities for constructing nanoscale devices. To
understand the desorption mechanism we have measured the dependence of the desorption rate on current and
sample bias. We find that it is possible to desorp H at both bias conditions and the dependence on current follows a
powerlaw. This indicates that the physical mechanism is vibrational heating of the hydrogen atom, due to inelastic
tunneling electrons. The experimental data is modeled with a new first principles theory for inelastic tunneling
between a real surface and a model probe tip, and we find quantitative agreement between the first principles
calculation and the experimental data. At positive sample bias the mechanism is inelastic scattering of tunneling
electrons with the Si-6sigma* resonance. At negatives sample bias eletrons tunnel from the surface towards the tip,
leaving a hole behin. This process can be described by a tunneling hole, and the desorption is due to inelastic
scattering of the hole with the Si-H 5sigma resonance.