Open AccessStructural Properties and Sensing Performance of CeYxOy Sensing Films for Electrolyte–Insulator–Semiconductor pH Sensors
Author(s) -
Tung-Ming Pan,
ChihWei Wang,
Ching-Yi Chen
Publication year - 2017
Publication title -
scientific reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.24
H-Index - 213
ISSN - 2045-2322
DOI - 10.1038/s41598-017-03209-7
Subject(s) - x ray photoelectron spectroscopy , annealing (glass) , analytical chemistry (journal) , electrolyte , isfet , stoichiometry , materials science , semiconductor , redox , chemistry , inorganic chemistry , electrode , chemical engineering , voltage , optoelectronics , physics , chromatography , transistor , quantum mechanics , field effect transistor , engineering , composite material
In this study we developed CeY x O y sensing membranes displaying super-Nernstian pH-sensitivity for use in electrolyte–insulator–semiconductor (EIS) pH sensors. We examined the effect of thermal annealing on the structural properties and sensing characteristics of the CeY x O y sensing membranes deposited through reactive co-sputtering onto Si substrates. X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy revealed the structural, morphological, and chemical features, respectively, of the CeY x O y films after their annealing at 600–900 °C. Among the tested systems, the CeY x O y EIS device prepared with annealing at 800 °C exhibited the highest sensitivity (78.15 mV/pH), the lowest hysteresis voltage (1.4 mV), and the lowest drift rate (0.85 mV/h). Presumably, these annealing conditions optimized the stoichiometry of (CeY)O 2 in the film and its surface roughness while suppressing silicate formation at the CeY x O y –Si interface. We attribute the super-Nernstian pH-sensitivity to the incorporation of Y ions in the Ce framework, thereby decreasing the oxidation state Ce (Ce 4+ → Ce 3+ ) and resulting in less than one electron transferred per proton in the redox reaction.