COMPARISON OF THE HYSTERESIS OF TA2O5 AND SI3N4 PH-SENSING INSULATORS

It has been shown that the accuracy of pH sensor devices based on insulator/electrolyte interfaces is limited by a slow response, which manifests itself as hysteresis and drift. In this paper, we use hysteresis measurements to compare the performance of Ta2O5 and Si3N4 as pH-sensing surfaces. The results depend on the time taken to perform a complete pH loop. At short loop times (960-9600 s) Ta2O5 is superior to Si3N4, by a factor of at least five. At longer loop times, Ta2O5 starts showing more hysteresis, and its advantage over Si3N4 is reduced. These data can be combined with earlier measurements of the hysteresis of Al2O3 surfaces to establish the following order of hysteresis magnitude at a loop time of 1920 s: Si3N4 > Al2O3 > Ta2O5.