Adsorption equilibria and kinetics of H2 at nearly ideal (2 x 1) Si(1 0 0) inner surfaces

Silicon nanocavities can be terminated with hydrogen by wet chemical etching. Their infrared spectra can to a large extent be interpreted in terms of silicon monohydrides on H(7 x 7) Si(1 1 1), H(1 x 1) Si(1 1 1) and H(2 x 1) Si(1 0 0), and of silicondihydrides on H(1 x 1) Si(1 0 0). The time evolution under isothermal conditions (600 °C) of the (1 0 0) faces admits a description in terms of transformation from H(1 x 1) Si(1 0 0) into (2 x 1) Si(1 0 0) with simultaneous H2 adsorption onto (2 x 1) Si(1 0 0) neat dimers. In so doing the inner H2 pressure decreases by about one order of magnitude from the initial value of 3000 Torr. The unique properties of nanocavities allow their use as nanoreactors; this has led to the determination of the sticking coecient for H2 adsorption in conditions of pressure, temperature and adventitious contamination otherwise not achievable.