| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 89 === Ion-sensitive field effect transistors (ISFET's) have many advantages than the conventional ion selective electrode. Small size, fast response and compatible with conventional IC technologies were the most important advantages. The general structure of ISFET was the same with MOSFET, but the main difference is that the metal gate in MOSFET was replaced by reference electrode/electrolyte/insulator(ionic sensor membrane) structure in ISFET. The insulator surface will suffer the change of potential as the is sample immersed into electrolyte, by which, we can measure the pH or other ionic concentration.
In this thesis the amorphous lead titanate (a-PbTiO3) thin film was prepared by sol-gel method to be the sensor gate of ISFET. The lead titanate thin films were deposited on SiO2(1000Å)/p-Si substrates, and the EIS structure was obtained. The flat-band voltage(ΔVBF) can be shifted by C-V measurement. The optimum conditions were found that the firing temperature was about 4000C and thin film thickness was about 0.5 �慆, and the sensitivity of about 53~58 mV/pH in the range of pH2~pH12 can be obtained.
The a-PbTiO3 membranes were also deposited on SiO2 gate ISFET devices. The threshold voltage was obtained by I-V measurement in different electrolyte. The sensitivity of the ISFET is about 53~58 mV/pH. Finally, the nonideal factors of the ISFET, such as drift, hysteresis, response stable time and life time were studied. The results show that the a-PbTiO3 gate ISFET exhibits a highly stable behavior.
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