The influence of the pH on the electrolyte-SiO2-Si system studied by ion-sensitive fet measurements and quasi-static C-V measurements

The responses of ion-sensitive FETs (ISFETs) with thermally grown SiO2 gate regions and of electrolyte-SiO2-Si (EOS) structures to stepwise changes in the pH were studied. In addition to a change in the boundary potential at the electrolyte-SiO2 interface which accounts for the observed initial response of ISFETs, a mechanism is also proposed in which one or other hydrogen-bearing species interacts with the surface states at the SiO2-Si interface. This proposed mechanism is based on the observed time drift in the response of ISFETs and on the changes in the shape of the quasi-static C-V curves of the EOS structures.