Positive charge which was created at the interface, by Li diffused through the substrate, was compared with the charge that was produced at the interface by H exposure. The charged centers which were created in both cases were thermally stable up to 400C, showed no correlation with the presence of dangling-bond defects at the interface and were located in the oxide; at about 0.2nm above the Si substrate plane. It was suggested that the impurity atoms (H, Li) were bonded to the first layer of bridging O atoms in impurity-induced valence-alternation states: that is, [Si2=OH]+ and [Si2=OLi]+. It was proposed that decomposition of the positively charged state at high temperatures was involved in the observed impurity-assisted bond-breaking at the interface.

Trapping of H+ and Li+ Ions at the Si/SiO2 Interface. V.V.Afanasev, A.Stesmans: Physical Review B, 1999, 60[8], 5506-12