High-Performance Electrolyte–Insulator–Semiconductor pH Sensors Using High- CeO2 Sensing Films

(EIS) sensor using a high-κ CeO₂ sensing membrane, which was deposited on a Si substrate through sputtering. We used X-ray diffraction and X-ray photoelectron spectroscopy to study the structural properties of these films that were annealed at various temperatures. The CeO₂ EIS sensor annealed at 900 °C exhibited a higher sensitivity of 64.8 mV/pH, lower hysteresis voltage of 1 mV, and smaller drift rate of 0.78 mV/h compared with other annealing temperatures, presumably suggesting the formation of a well-crystallized CeO₂ film featuring a high dielectric constant and having a high fraction of Ce³⁺.