Impact of yttrium concentration on structural characteristics and pH sensing properties of sol-gel derived Y₂O₃ based electrolyte-insulator-semiconductor sensor

The complementary metal-oxide-semiconductor compatible electrolyte-insulator-semiconductor (EIS) platform is a promising tool for the detection of ions and biomolecules. In this investigation, we fabricated a Y₂O₃ sensing membrane based EIS pH sensor by Pechini sol-gel method. X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy were implemented to analyze the effect of yttrium concentration (0.1, 0.2 and 0.3 M) on the crystalline structure, surface morphology and chemical composition of the sensing membrane, respectively. The Y₂O₃ based EIS sensor fabricated under the 0.2 M concentration manifests the near-super-Nernstian pH response (63.80 mV/pH) and high stability in terms of a low hysteresis voltage (5.7 mV) and a small drift rate (0.18 mV/h). We ascribe that the optimal yttrium content increases the surface roughness of the sensing membrane and the formation of a well-crystallized Y₂O₃ film as well as a stoichiometric Y₂O₃ film.