Comparison of structural and sensing characteristics of Pr2O3 and PrTiO3 sensing membrane for pH-ISFET application

In this paper, we investigated on the structural properties and sensing characteristics of Pr2O3 and PrTiO3 sensing membrane deposited on Si substrates by reactive rf sputtering. The structural and morphological features of these films with annealing at various temperatures were studied by X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy. Compared with Pr2O3 sample, electrolyte–insulator–semiconductor devices with a high-k PrTiO3 sensing film annealed at 800 °C exhibit good sensing characteristics, including a high sensitivity of 56.8 mV/pH in the solutions from pH 2 to pH 12, a small drift rate of 1.77 mV/h in the pH 7 buffer solution, and a low hysteresis voltage of 2.84 mV in the pH 7 → 4 → 7 → 10 →7. The improvement can be explained by the formation of a thinner interfacial SiO2 and silicate layer, and the higher surface roughness.