Adsorption equilibria and kinetics of H 2 at nearly ideal (2 × 1)Si(100) inner surfaces

Abstract

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 × 7)Si(111), H(1 × 1)Si(111) and H(2 × 1)Si(100), and of silicon dihydrides on H(1 × 1)Si(100). The time evolution under isothermal conditions (600 °C) of the (1 0 0) faces admits a description in terms of transformation from H(1 × 1)Si(100) into (2 × 1)Si(100) with simultaneous H 2 adsorption onto (2 × 1)Si(100) neat dimers. In so doing the inner H 2 pressure decreases by about one order of magnitude from the initial value of 3 × 10 3 Torr. The unique properties of nanocavities allow their use as nanoreactors; this has led to the determination of the sticking coefficient for H 2 adsorption in conditions of pressure, temperature and adventitious contamination otherwise not achievable.