Structural properties and sensing performance of CeTiO3 ceramic films as a solid-state pH sensor

In this paper, we have studied the impact of postannealing treatment on the structural properties and sensing characteristics of CeTiO3 ceramic membranes deposited on Si substrate by sputtering for solid-state electrolyte-insulator-semiconductor (EIS) pH sensors. X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction, and atomic force microscopy were used to study the chemical compositions, elemental depth profiles, film structures, and surface morphologies of CeTiO3 ceramic membranes treated at three rapid thermal annealing (RTA) temperatures of 700, 800 and 900 °C. The sensing performance of the CeTiO3 ceramic membranes annealed at three different RTA temperatures is strongly correlated to their structural properties. The CeTiO3 EIS device after RTA at 800 °C exhibited the best sensing characteristics (pH sensitivity, hysteresis voltage and drift rate) among these RTA temperatures. We attribute this behavior to the optimal RTA temperature enhancing the Ce3+/Ce4+ ratio of CeTiO3 ceramic membrane, reducing an interfacial layer at the CeTiO3-Si interface, and increasing its surface roughness.