High-sensitivity pH sensor employing a sub-micron ruthenium oxide thin-film in conjunction with a thick reference electrode

We demonstrate the feasibility of developing a low-cost, rugged, miniaturized ruthenium oxide (RuO2) thin-film pH sensor comprising a RuO2 on platinum sensing electrode deposited using R.F. magnetron sputtered in conjunction with an integrated thick Ag/AgCl reference electrode. A RuO2 thin-film (300 nm) is deposited on an alumina substrate using R. F. magnetron sputtering with a RuO2 sputtering target in Argon plasma. Experimental results show a linear pH sensitivity of 58.50 mV/pH when the developed sensor is immersed in a standard buffer solution having pH values of 4.0 and 10.0 and lab supply water of pH 7.7 at a temperature of 22 °C. These results are in excellent agreement with the theoretical Nernstian response of 58.56 mV/pH at 22 °C.