pH sensitivity and hysteresis of a-WO3 gate ISFET compared with different membranes

Because of the pH sensitivity is one of the important characteristic parameters of ISFET devices. The response of ISFET is mainly determined with the type of the sensing membrane, therefore the sensing material plays a significant role. In addition, the hysteresis is the non-ideal and unstable factor of ISFET devices for measuring, Hence, in this study, the pH sensitivity and hysteresis of a-WO3 gate ISFET are investigated, and compare with different sensing membranes. In this paper, the pH sensitivities of the different gate ISFET devices were measured in different solutions by the I-V curve of measuring system, and the hysteresis curves were measuring by exposing several cycles of pH values at different loop time. According to the experimental results, a-WO3, Ta2O5 and a-Si:H have high response, the pH sensitivities are over 50mV/pH, However, it is also found that the hysteresis of a-WO3 gate ISFET is dependent on measuring loop time and measuring path, and hysteresis width is increasing with loop time and measuring path.