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In order to develop a pH sensor having a good pH-sensing characteristic, electrolyte-insulator-semiconductor capacitors using a high-k P2O3 thin film as the sensing membrane were fabricated on silicon substrates by 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. The Pr2O3 sensing film after annealing at 900degC is suggested to the increase in the interfacial SiO2 and silicate formation, and the high surface roughness. Therefore, a physical vapor deposition Pr2O3 film is adopted as a new pH-sensing layer. The result produces a pH response of 52.9 mV/pH (pH=2-12), a hysteresis voltage of 17.5 mV (pH=7 rarr 4 rarr 7rarr 10 rarr 7), and a drift rate of 2.15 mV/h (pH=7 buffer solution).

In this paper, we investigated on the structural properties and sensing characteristics of Pr2O3 and PrTiO3 sensing membrane deposited on Si substrates by reactive rf 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 Pr2O3 sample, electrolyte–insulator–semiconductor devices with a high-k PrTiO3 sensing film annealed at 800 °C exhibit good sensing characteristics, including a high sensitivity of 56.8 mV/pH in the solutions from pH 2 to pH 12, a small drift rate of 1.77 mV/h in the pH 7 buffer solution, and a low hysteresis voltage of 2.84 mV in the pH 7 → 4 → 7 → 10 →7. The improvement can be explained by the formation of a thinner interfacial SiO2 and silicate layer, and the higher surface roughness.

This paper describes the physical and sensing characteristics of Y 2 O 3 sensing membrane grown on Si substrates through reactive rf sputtering. The structural and morphological features of these films were investigated using X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy. We find that the electrolyte-insulator-semiconductor structure with Y 2 O 3 sensing membrane prepared under an argon-to-oxygen flow ratio of 25/5 and annealed at 800 °C exhibited a higher sensitivity of about 54.5 mV/pH in the solutions from pH 2 to pH 12, a smaller drift rate of 2 mV/h in the pH 7 buffer solution, and a lower hysteresis voltage of 4.78 and 6.39 mV in the pH 7 → 4 → 7 → 10 → 7 and pH 7 → 10 → 7 → 4 → 7 loops, respectively. We attribute this behavior to (a) the presence of small amounts of oxygen in the sensing film preventing Y-silicate or amorphous silica from forming at the Y 2 O 3 /Si interface and (b) the low surface roughness.

The structural properties and sensing characteristics of Y2O3 sensing membrane were deposited on silicon substrates by reactive rf 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. It was found that Y2O3 sensing dielectrics annealed at 800 °C exhibit a high sensitivity of 56.09 mV/pH in the solutions from pH 2 to pH 12, a low hysteresis voltage of 13.6 mV in the pH 7 → 4 → 7 → 10 → 7, and a small drift rate of 1.24 mV/h in the pH 7 buffer solution. This annealing condition is suggested for the reduction of the interfacial SiO2 and silicate formation, and the small surface roughness due to the well-crystallized Y2O3 structure.

In this paper, we reported an Y2O3 gate sensing membrane prepared under three flow conditions and deposited on Si substrate by rf sputtering. The optimal conditions were found to be an argon-to-oxygen flow ratio of 25/5 and an annealing temperature of 800 degC. In that case, the physical vapor deposition films are the reduction of lower-k interfacial layer and Y-silicate film formation from XPS and the smoothest of surface roughness from AFM. The high-k Y2O3 EOS exhibits a high sensitivity, a small drift rate and a low hysteresis voltage.

In this paper, the physical and sensing properties of physical vapor deposition Pr2O3 dielectrics deposited on Si substrate were explored. A 30 nm Pr2O3 dielectric was grown on the p-type Si (100) wafer by reactive RF sputtering from a praseodymium target with a argon-to-oxygen (Ar/O2) flow ratio of 10/4. Post deposition annealing of the samples was carried out using a conventional rapid thermal annealing (RTA) system in O2 ambient for 30-s at different temperatures. A 300-nm Al was deposited on the backside of Si wafer by thermal evaporator. The sensing area was defined by a photosensitive epoxy. The pH sensitivities of Pr2O3 sensing films were all extracted by capacitance-voltage (C-V) curves of EIS structures. C-V curves for various pH buffer solutions of Merck Inc. were measured through Ag/AgCl reference electrode by Hewlet-Packard 4284A.