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Fabrication and Functionalization of In2O3 Thin Film Transistors for Biosensing Applications
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Due to unprecedented interest in the development of new ways of detection,
quantification and monitoring of different molecules and compounds, the biosensor
arises as the most promising approach to fulfil such requirements [1]. The biosensor is
a device which can detect and quantify the presence of certain chemical compounds or
biological reactions by the use of electrical, thermal or optical signals. Combining this
with the advantages of microelectronic technologies, such as well developed
miniaturization and ability to amplify and control an input, biosensors based on TFTs
are currently the most studied devices for this kind of applications [2].
The goal of this dissertation was to fabricate In2O3-based TFTs functionalized with 3-
aminopropyltriethoxysilane (APTES) to work as pH sensors. For that several concepts
were used: using Al electrodes and an insulator layer, SU-8; and using Cr/Au electrodes
with two different designs, planar and interdigitated. The devices with best performance
were the ones with Cr/Au electrodes and planar configuration. The functionalization and
liquid-gating of these devices are successfully demonstrated in this work. However, a
cleaning method had to be established in order to measure the same sample several
times. The APTES film showed poor stability to the cleaning method performed. This
poor stability can be due to siloxane bond hydrolysis catalyzed by the amine group
which could also cause uncontrolled polymerization/oglimerization of the amine groups
[3]. Both will lead to a decrease in the device’s performance. The measurement
procedure and/or the cleaning method of the sample will have to be optimized in the
future.