Structural properties and sensing characteristics of high-k Ho2O3 sensing film-based electrolyte–insulator–semiconductor

In this study, we report a Ho2O3 electrolyte–insulator–semiconductor (EIS) device films deposited on Si substrates through reactive sputtering. The effect of thermal annealing (700, 800, and 900 °C) on the structural and surface properties of Ho2O3 sensing film was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. We found that the EIS device with a Ho2O3 sensing film annealed at 800 °C exhibited a higher sensitivity of ∼57 mV/pH, a lower hysteresis voltage of 2.68 mV, and a smaller drift rate of 2.83 mV h−1 compared to those at other annealing conditions. This improvement can be attributed to the well-crystallized Ho2O3 structure and the large surface roughness.