Structural and Sensing Characteristics of Dy₂O₃ and Dy₂TiO₅ Electrolyte−Insulator−Semiconductor pH Sensors

Abstract

In this paper, we describe an electrolyte−insulator−semiconductor device for biomedical engineering applications prepared from Dy 2 O 3 and Dy 2 TiO 5 sensing membranes deposited on Si substrates by means of reactive radio frequency 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 the Dy 2 O 3 film, electrolyte−insulator−semiconductor devices incorporating a Dy 2 TiO 5 sensing film annealed at 800 °C exhibited a higher sensitivity (57.59 mV/pH in the solutions from pH 2 to 12), a smaller hysteresis voltage (0.2 mV in the pH loop 7 → 4 → 7 → 10 → 7), and a lower drift rate (0.362 mV/h in the pH 7 buffer solution), presumably because of its thinner low- k interfacial layer at the oxide/Si interface and its higher surface roughness.