Study on the Ruthenium Dioxide Sensing Membrane as pH Array Sensors with Real Time Measurement System

In this paper, we use the ruthenium oxide sensing membrane as the sensing layer of the ion selective electrodes for the pH array sensors. The ruthenium oxide sensing membrane that was deposited on the silicon wafer substrate by radio frequency sputtering technology. First, we put the silicon substrate into the chamber for pre-sputtering for 10 min at 70 W In this experiment, the sputtering total operating pressure of 10mtorr in argon mixed O2 gas (Ar = 40 sccm、O2 = 10 sccm) for 1 hour was achieved and the radio frequency power was 100W, at 13.56MHz. Finally, we obtained the RuO2 sensing membrane of the EIS pH sensor device. We also measured the IDS-VG curves of the RuO2 sensing membrane, which connected to MOSFET with conducting wire and immersed in the pH buffer solutions that have different pH values by the Keithley 236 Instrument. By the experimental results, we can obtain the value of the average pH sensitivity of the sputtering prepared RuO2 sensing membrane of the EIS devices in the different buffer solutions, which is about 55.44 mV/pH. In this study, the real time measurement system includes array readout circuits, one USB data acquisition card and the visual basic windows development software to design the windows measurement interface. We used the USB data acquisition card to detect the sensing signal of the readout circuit and the results were shown at the windows interface.