The effects of sensing electrode thickness on ruthenium oxide thin-film pH sensor

A miniaturised pH sensor structure employing an R.F. sputtered ruthenium oxide sensing thin-film electrode in conjunction with an electroplated Ag/AgCl reference electrode is developed and the effect of the thickness of the sensing electrode on the measurement accuracy is investigated. Experimental results show that the pH sensor exhibits Nernstian slopes of 66.52 mV/pH, 68.63 mV/pH, 67.73 mV/pH, and 54.83 mV/pH for ruthenium oxide film thicknesses of 425, 300, 175 and 50 nm, respectively. All the pH measurements were carried out at a temperature of 22 degrees C. The performance and characterisation of the pH sensors in terms of sensitivity, response time, pH resolution, stability and reversibility are discussed. (C) 2014 Elsevier B.V. All rights reserved.