Effect of surface functional groups on the pH sensitivity in ion-sensitive field effect transistors

For ion-sensitive devices with SiO
₂
sensing membrane, the pH sensitivity response has been analyzed when additional functional groups are attached on the SiO
₂
membrane. A modified Site-Binding model (SBM) and Gouy-Chapman-Stern (GCS) model are used for the theoretical analysis. In the presence of both silanol and amine groups, the highest pH sensitivity can be achieved at a functional group ratio of 1:3 or 3:1. The differential capacitance and intrinsic buffer capacity were also compared in order to understand their effects on pH sensitivity.