Positive charge created at the Si/SiO2 interface by lithium diffused through the substrate silicon is compared with the charge produced at this interface by hydrogen exposure. The charged centers created in both cases are thermally stable up to 400 degrees C, show no correlation with the presence of dangling-bond defects at the Si/SiO2 interface. and are spatially located in the oxide at 2 +/- 1 Angstrom above the Si substrate plane. The impurity atoms (H, Li! are suggested to be bonded to the first layer of bridging oxygens in impurity-induced valence-alternation states, i.e., [Si-2=OH](+) and [Si-2=OLi](+). It is hypothesized that the decomposition of the positively charged state at elevated temperatures is involved in the observed impurity-assisted bond breaking at the Si/SiO2 interface. [S0163-1829(99)03628-0].