Effect of atomic hydrogen on the acetylene-absorbed Si(100)(2x1) surface at room temperature

High resolution electron energy loss spectroscopy, low energy electron diffraction and quadrupole mass spectrometer (QMS) have been employed to study the effect of atomic hydrogen on the acetylene-saturated pre-adsorbed Si(100)(2 x 1) surface and the surface phase transition at room temperature. It is evident that the atomic hydrogen has a strong effect on the adsorbed C2H2 and the underlying surface structure of Si. The experimental results show that CH and CH2 radicals co-exist on the Si surface after the dosing of atomic hydrogen; meanwhile, the surface structure changes from Si(100)(2 x 1) to a dominant of (1 x 1). These results indicate that the atomic hydrogen can open C=C double bonds and change them into C-C single bonds, transfer the adsorbed C2H2 to C2Hx (x = 3,4) and break the underlying Si-Si dimer, but it cannot break the C-C bond intensively. The QMS results show that some C-4 species are formed during the dosing of atomic hydrogen. It may be the result of atomic hydrogen abstraction from C2Hx which leads to carbon catenation between two adjacent C-C dimers. The C-4 species formed are stable on Si(100) surfaces up to 1100 K, and can be regarded as the potential host of diamond nucleation.