Thermodynamic and kinetic stability with respect to hole trapping. of silanic bonds at the Si-SiO 2 interface

The thermodynamic and kinetic stabilities of the Si–H bonds at the Si–SiO2 interface are studied on the basis of high-level quantum-mechanical calculations in the framework of density-functional theory. In the absence of an applied electric field, the silanic bond is shown to be stable with respect to both hole capture from the top of the silicon valence band and electron loss to the bottom of the silicon conduction band, but unstable with respect to hole capture from the top of the SiO2 conduction band. The positively charged hydrogen does not shift spontaneously to protonate a neighbouring siloxanic bridge unless it contains one adsorbed water molecule at least. The protonated siloxanic site thus formed may restore the original silanic site (via simultaneous electron capture from the conduction band and hydron shift to silicon) but also evolve spontaneously to a hydrogen atom via simple electron capture.