Preparation and study on the drift and hysteresis properties of the tin oxide gate ISFET by the sol-gel method

The drift and hysteresis are important factors that influence the output accuracy of the pH ion sensitive field effect transistor (pH-ISFET). In this paper, we use the sol-gel process to prepare the tin oxide (SnO2) sensing membrane. Then, use the constant voltage constant current circuit and voltage-time recorder to record the output voltage of the SnO2 gate pH-ISFET. The measurement of the drift was carried out separately in pH 1-9 buffer solutions for 12 h. From the experimental results, we can find that the drift rate is increasing with pH value. We also use constant voltage constant current circuit to measure the hysteresis width of the SnO2 gate pH-ISFET for pH loop pH 4-1-4-7-4 and pH 5-1-5-9-5 cycle loops for the different loop time, respectively. From experimental results, we can conclude that the hysteresis width is proportional to the loop time. (C) 2002 Elsevier Science B.V. All rights reserved.