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Optical Engineering

Sensitivity and hysteresis properties of a-WO3, Ta2O5 , and a-Si:H gate ion-sensitive field-effect transistors
Author(s): Jung Lung Chiang; Jung Chuan Chou; Ying-Chung Chen
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Paper Abstract

The sensitivity and hysteresis effects of ion-sensitive fieldeffect transistor (ISFET) devices based on a-WO3, Ta2O5 , and a-Si:H thin films have been investigated. The pH sensitivity is one of the important characteristic parameters of ISFET devices, and the response of an ISFET is mainly determined by the type of the sensing membrane; therefore the sensing material plays a significant role. Furthermore, hysteresis leads to inaccuracy and instability of ISFET measuring devices. In this investigation the pH sensitivities of different sensing-gate ISFET devices were measured in different buffer solutions by current-voltage (I -V) measurement, and the hysteresis curves were measured by exposing the device to several cycles of pH values over different loop times. According to the experimental results, a-WO3 and a-Si:H are useful in acidic buffer solutions (pH 1 to 7), and Ta2O5 at pH 1 to 12. The pH sensitivities are all larger than 50 mV/pH, and it was found that the key parameter in determining the hysteresis width is the loop time.

Paper Details

PDF: 7 pages
Opt. Eng. 41(8) doi: 1117/1.1482099
Published in: Optical Engineering Volume 41, Issue 8, August 2002
Show Author Affiliations
Jung Lung Chiang, National Sun Yat-Sen Univ. (Taiwan)
Jung Chuan Chou, National Yunlin Univ. of Science and Technology (Taiwan)
Ying-Chung Chen, National Sun Yat-Sen Univ. (Taiwan)


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