Influence of Ti content on sensing performance of LaTixOy sensing membrane based electrolyte-insulator-semiconductor pH sensor

Abstract In this article, we explored the ability of inorganic LaTixOy (LTO) sensing materials grown on bare p-type substrate to be used as a pH electrolyte-insulator-semiconductor (EIS) sensor. Herein, we fabricated the LTO EIS sensors through the sol-gel synthesis technique under the 0.2 M condition with subsequent annealing at 800 °C in O2 ambient for 20 min. In order to avoid the generation of hydration layer of the gate insulator and reduce the formation of La-silicate, we doped Ti into the La2O3. The structural properties, surface morphologies, film micromorphologies, and chemical states of the sensing films have been investigated by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy analyses, respectively. The sol-gel derived La2Ti2O7 sensing film exhibited super Nernstian pH sensitivity of 68.17 mV/pH with a linearity of 0.999. From the reliability point of view, the La2Ti2O7 sensor showed the best long-term stability with a lower drift rate of 0.21 mV/h as well as a smaller hysteresis voltage of 0.7 mV, as compared with other combination of LTO films. This finding behavior might be due to the high Ti content into the La2Ti2O7 film reducing the silicate layer and increasing the surface sites.