Development of an FET-Type Reference Electrode for pH Detection

This work is dedicated to developing of a FET-type reference electrode (REFET) for dissolved hydrogen-ion detection. The total size of a fabricated chip is 0.8×0.4 mm. The surface of one ISFET gate, which is to be serve as the REFET, is engineered to its minimize pH sensitivity by applying a polymer double layer (PVC/OMR83). The REFET alone exhibited a sensitivity of 0.7 mV/pH, which showed a drastic decrease in the pH sensitivity compared to that of a pH-ISFET (about 56.5 mV/pH). A showed a sensitivity of 55.4 mV/pH. The average change in the sensitivity was about 1.2 mV/pH during a repeated measurements for 35 days.