Spin polarization of the Si(111)-7 × 7 surface: A study with a spin-polarized metastable helium atom beam

We have observed the electron spin polarization of a clean Si(111) surface under external magnetic fields of 0–5 T using a spin-polarized metastable helium atom beam. By making comparisons with metastable deexcitation spectroscopy (MDS) measurements, the spin polarization has been assigned to surface dangling bonds. It has been found that the spin polarization is largely quenched by the adsorption of atomic hydrogen, and that its H-exposure dependence correlates well with that of the MDS spectrum and the low energy electron diffraction pattern.