Ion-sensitive field-effect transistor with silicon nitride gate for pH sensing

Abstract

Abstract An ion-sensitive field-effect transistor (ISFET) has been fabricated with silicon nitride as the gate to provide a pH-sensing membrane. Measurements of pH sensitivity, selectivity, hysteresis effect and long-term stability have been made. The pH sensitivity is 46 mV per pH. The chemical response to the K+ ion is higher than that for the Na+ ion for this device. The long-term drift is about 1 mV per hour after a ten-hour immersion. Results for an oxide gate ISFET are also shown for comparison.