Observations of H2 adsorption on the (100) surface were performed by using scanning tunnelling microscopy. Pre-dosing the surface with atomic H led to the efficient adsorption of H2 in an inter-dimer configuration of adjacent singly-occupied dimers. This strong and local promotion of dissociative adsorption was explained by the non-interacting character of the relevant dangling bonds. On the other hand, H2 sticking was strongly inhibited on clean (100)-(2 x 1) surfaces; where the dangling bonds were rendered less reactive by their mutual interaction.

Dissociative Adsorption of H2 on Si(100) Induced by Atomic H A.Biedermann, E.Knoesel, Z.Hu, T.F.Heinz: Physical Review Letters, 1999, 83[9], 1810-3