Postdeposition Anneal on Structural and Sensing Characteristics of High-   Electrolyte–Insulator–Semiconductor pH Sensors

In this letter, we develop an electrolyte-insulator-semiconductor (EIS) device using a high- κ Er₂ TiO₅ sensing membrane deposited on a Si substrate through cosputtering. We used X-ray diffraction and X-ray photoelectron spectroscopy to study the structural properties of these films annealed at various temperatures. The EIS device incorporating an Er₂ TiO₅ sensing film annealed at 900^°C exhibited a higher sensitivity of 58.4 mV/pH, a lower hysteresis voltage of 4.6 mV, and a smaller drift rate of 1.2 mV/h than other annealing temperatures, presumably suggesting the formation of a well-crystallized Er₂TiO₅ film and a thinner silicate layer at the oxide/Si interface.