Hydrogen adsorption on Si(100)-2×1 surfaces studied by elastic recoil detection analysis

Hydrogen adsorption on a clean Si(100)-2×{}1 surface has been studied by the high-energy ion- beam method (6-MeV F³⁺) combined with low-energy electron diffraction. We report that (1) the saturation coverage of hydrogen on a clean Si(100)-2×{}1 surface kept at room temperature is 1.85±{}0.18 monolayers (ML), and (2) the first 1-ML hydrogen adsorbs rather quickly, leading to a 2×{}1-H phase, while adsorption of more hydrogen beyond 1 ML occurs very slowly, approaching a saturated structure of 1×{}1-H. The effect of substrate temperatures on adsorption is also studied.