A computational study on the energetics and mechanisms for the dissociative adsorption of SiH _x (x = 1-4) on W(1 1 1) surface

The adsorption and dissociation mechanisms of SiH _x (x = 1-4) species on W(1 1 1) surface have been investigated by using the periodic density functional theory with the projector-augmented wave approach. The adsorption of all the species on four surface sites: top (T), bridge (B), shallow (S), and deep (D) sites have been analyzed. For SiH ₄ on a top site, T-SiH _4(a) , it is more stable with an adsorption energy of 2.6 kcal/mol. For SiH ₃ , the 3-fold shallow site is most favorable with adsorption energy of 46.0 kcal/mol. For SiH ₂ , its adsorption on a bridge site is most stable with 73.0 kcal/mol binding energy, whereas for SiH and Si the most stable adsorption configurations are on 3-fold deep sites with very high adsorption energies, 111.8 and 134.7 kcal/mol, respectively. The potential energy surfaces for the dissociative adsorption of all SiH _x species on the W(1 1 1) surface have been constructed using the CINEB method. The barriers for H-atom migration from SiH _x(a) to its neighboring W atoms, preferentially on B-sites, were predicted to be 0.4, 1.0, 4.5 and, 8.0 kcal/mol, respectively, for x = 4, 3, 2, and 1, respectively. The adsorption energy of the H atom on a bridge site on the clean W(1 1 1) surface was predicted to be 65.9 kcal/mol, which was found to be slightly affected by the co-adsorption of SiH _x-1 within ± 1 kcal/mol.