Fabrication and Characterization of a Ruthenium Nitride Membrane for Electrochemical pH Sensors

The pH sensing and nonideal characteristics of a ruthenium nitride (RuN) sensing membrane pH sensor were investigated. RuN thin films were deposited from a 99.9% ruthenium target on p-type silicon substrates using radio frequency (r.f.) sputtering with N(2) gas. Subsequently, the nanometric structure and surface morphology of RuN thin films were determined. The sensitivity of the RuN sensing membrane pH sensor was 58.03 mV/pH, obtained from I(D)-V(G) curves with a current-voltage (I–V) measurement system in standard buffer solutions from pH 1 to pH 13 at room temperature (25 °C). Moreover, the nonideal characteristics of the RuN sensing membrane, such as temperature coefficient, drift with light influence, drift rate and hysteresis width, etc. were also investigated. Finally, the sensing characteristics of the RuN membrane were compared with titanium nitride (TiN), aluminum nitride (AlN) and silicon nitride (Si(3)N(4)) membranes.