Nov 2023
Abstract
In the last decades, metal oxide semiconductors and thin-film transistors (TFTs) have gained significant interest in the design of modern electronics to develop beyond silicon technology across a wide variety of digital-age applications. That includes fast-developing technologies like the Internet of Things (IoT), robotics, and the healthcare sector where the world’s demand for a rapid, efficient, and inexpensive biosensor has been increasing since the global pandemic in 2020. Fabricating TFT as a platform for various electronic interfaces requires advanced materials design and device architecture. In this thesis, we explored In2O3/ZnO TFT as a novel TFT sensor. The device engineering combines the novel hetero-structure metal oxide channel that can sustain a 2-dimensional electron gas (2DEG) which leads to higher mobility and a novel tri-channel design for source/drain (S/D) electrodes. This design has a wide sensing channel that allows oxide surface functionalization capacity to create a highly sensitive sensor.
In the first part, we demonstrate the first-ever In2O3/ZnO heterojunction TFTs fabricated by RF sputtering. Using these devices as our testbed, we studied the impact of the individual layer thicknesses on electron distribution and transport across and along the transistor channel. Further analysis of the device’s surface morphology and stability have been investigated.
In the second part, we introduce the S/D electrodes’ geometrical modification to facilitate the sensing process. The optimized structure of the In2O3/ZnO heterojunction TFT in part I has been fabricated on high-k dielectric to enable low voltage operation and transparency properties that can be utilized in sensing applications. The device’s structure is built on a glass substrate with different gate electrodes and gate dielectric thicknesses, and the effect of each configuration has been investigated.
In the third part, the implementation of the fabricated device for bio-sensing is introduced. We delve into the strategies employed for functionalization using common biosensor linkers. We showcase the deployment of the designed sensor to detect glucose, featuring enduring and consistent enzymatic functionality achieved through the immobilization of glucose oxidase enzyme. These sensors exhibit efficacy in detecting glucose levels in saliva among various other biological fluids.