Study on the characterizations and applications of the pH-Sensor with GZO/glass extended-gate FET

The GZO thin films of the thickness about 200~250nm were deposited on the glass which used as a pH sensor head based on the extended-gate field-effect transistor (EGFET) by r. f. sputtering system in this study. The pH sensing characteristics of the GZO/glass EGFET sensing structure were investigated and a semiconductor parameter analyzer (Keithley 4200) was used to measure the drain-source current versus gate-source voltage curves in various buffer solutions. In the experimental results, it can be obtained that the various pH sensitivities of the GZO pH-EGFET at different measuring temperature ambiance. Furthermore we also found that the pH sensitivity is increasing with temperature increased, and the pH response is a good linearity in this study. In addition, the GZO thin film was found that the resistance was about 8.37×10 -3 Ω-cm and the average of transmittance was about 80% in the visible range.