First-Principles Molecular-Dynamics Calculations on Chemical Reactions and Atomic Structures Induced by H Radical Impinging onto Si(001)2 × 1:H Surface

Chemical reactions between hydrogen terminated Si(001)2 × 1 surface and impinging H radical are investigated by means of first-principles molecular-dynamics simulations. Reaction probabilities of abstraction of surface terminating H atom with H₂ formation, adsorption onto Si surface and reflection of impinging H atom are analyzed with respect to the kinetic energy of incident H radical. The probabilities of abstraction and adsorption turn out to be ranging from 0.81 to 0.58 and from 0.19 to 0.42, respectively, while that of reflection almost zero. As initial kinetic energy of the impinging atom increases, the reaction probability of abstraction decreases and that of absorption increases. Metastable H-absorbed atomic configurations are also derived by optimizing the structures obtained in the impinging dynamics calculations. They are candidates of the so-called reservoir site which is a key to understand the unity hydrogen coverage observed after an exposure to gaseous H atom ambient despite existing residual vacant sites due to abstraction.