A NOVEL DESCRIPTION OF ISFET SENSITIVITY WITH THE BUFFER CAPACITY ANDDOUBLE-LAYER CAPACITANCE AS KEY PARAMETERS

The pH sensitivity of ISFETs arises from interactions of protons with ISFET gate surface sites. This sensitivity is described by a new simpl er model with the intrinsic buffer capacity and the differential, capa citance as key parameters. The obtained expression is independent of t he models used for the chemical surface equilibria and the charge prof ile in the solution. The general expression for the sensitivity is ela borated using the site-binding theory and the Gouy-Chapman-Stern theor y. The relatively high sensitivity of Ta2O5 ISFETs is explained using this elaborated theory. It is shown that the electrolyte concentration has almost no influence on the sensitivity of Ta2O5 ISFETs.