Positive charge was created at the interface due to Li diffusion through the Si substrate. This was compared with the charge which was produced at this interface by H exposure. The charged centres which were created in both cases were stable up to 400C, exhibited no correlation with the presence of dangling-bond defects at the interface and were located (in the oxide) at some 0.2nm above the substrate plane. Impurity atoms such as H and Li were suggested to be bonded, to the first layer of bridging O atoms, in impurity-induced valence-alternation states such as [Si2=OH]+ and [Si2=OLi]+.

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