Ionisation and trapping of hydrogen at SiO2 interfaces

Annealing of interfaces between SiO2 and (111)Si, (100)Si in H2 in the temperature range 450–800°C is found to introduce a considerable density (up to 1013 cm−2) of positively charged centres. There is no comparable density of dangling bonds initially present nor generated during the annealing at the Si/SiO2 interfaces or in the SiO2 layer that could account for the observed hydrogen bonding. Therefore, the hydrogen is suggested to be trapped in the positively charged valence alternation state 3-fold coordinated oxygen resembling the well known hydronium ion (H3O)+.