Study of structural properties and sensing performance of high performance sol-gel synthesized CeTi_xO_y sensing membranes

In this paper, we developed a very simple sol-gel spin-coating method to fabricate high performance CeTi_xO_y sensing membranes for a solid-state electrolyte-insulator-semiconductor (EIS) pH sensor. The surface morphologies, crystal structures, chemical compositions, and elemental depth profiles of the CeTi_xO_y membranes treated with three different titanium concentrations (0.1, 0.3 and 0.5 M) were studied using a combination of atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, respectively. The structural properties of the CeTi_xO_y membranes were corrected with the sensing performances of CeTi_xO_y EIS pH sensors. The sol-gel synthesized CeTi_xO_y EIS device prepared at the 0.3 M condition exhibited the best sensing characteristics (pH sensitivity, hysteresis voltage and drift rate) among these conditions. We attribute this behavior to the optimal titanium content in the sensing membrane enhancing the surface roughness CeTi_xO_y film, increasing the Ce³⁺/Ce⁴⁺ ratio, and forming the stoichiometric Ce₂TiO₅ structure.