Dr. Fu received his bachelor degree in materials science and engineering at Tsinghua University in 2003. He completed his doctorate degree at the Institute of Physics, Chinese Academy of Sciences in 2009 for pioneering research activities in integrating ferroelectrics into nanoscale transistors under the supervise of Prof. Enge Wang. After being as a visitor at Center for Nanophase Materials Sciences, Oak Ridge National Laboratory (ORNL), United States, Dr. Fu joined the Nanoelectronics group at the Department of Physics, University of Basel as a postdoctoral researcher working with Prof. Christian Schönenberger. He was involved in a cutting-edge Nano-Tera.ch RTD project NanowireSensor, aiming at integrating silicon nanowire field-effect transistors as the active sensor part in electronic point-of-care diagnostic devices. Concurrently, another focus of Dr. Fu is chemical vapor deposition (CVD) of graphene and its applications as biochemical sensors. His work revealed that ideal defect-free graphene is inert to the electrolyte composition changes in solution. In order to target graphene-based biochemical sensing platform, he demonstrated that noncovalent functionalization can indeed delivery graphene transistor sensors with fully preserved mobility. Recently, Dr. Fu explored the applications of graphene radiofrequency (RF) transistors for sensing. This work opens the avenue for further research on a new generation of biochemical sensors. Very recently, Dr. Fu was involved in the EU GRAPHENE Flagship project.
演讲题目：High-frequency Measurement of Graphene Transistor for Biosensing
内容摘要
Owing to its high carrier mobility, large surface-to-volume ratio, and chemical stability, graphene have drawn considerable attention as the building blocks for next generation label-free electrical biochemical sensors. Previously, we revealed that ideal defect-free graphene is inert to electrolyte composition changes in solution and non-covalent functionalization of graphene with chemically active groups has to be introduced for practical sensing applications. [1, 2] However, under physiological conditions, graphene sensors typically can not detect a biological stimuli occurring at a distance larger than a nanometer from its surface due to the present of movable ions (the so called “Debye screening length”). Consequently, graphene is therefore generally disregarded as a potent biological sensor.
The present work[3] serves to shed light on this distance-dependent sensing paradigm. We performed radiofrequency (RF) measurements at 2-4 GHz on electrolyte-gated graphene field-effect transistors (GFETs). At these high frequencies the ions in the electrolyte start to lag behind the alternating current (AC) electric field due to the viscosity of the solution. As a result, the Debye screening effect is canceled and the electrolyte behaves as a pure dielectric at RF/microwave frequencies. Consequently, the biomolecules could be probed beyond the Debye screening length. In this work, we started with chemical vapor deposition (CVD) graphene [4] grown on 25 um thick copper foils. The CVD graphene allows for the transfer of high-quality graphene with lateral scale of many centimeters on arbitrary substrates. Further characterizations indicate that we achieved predominant uniform, monolayer graphene with high mobility ~3000cm2/Vs. As shown in Fig. 1a and b, liquid-gated GFETs with reliable performance are developed. Then we performed RF measurements on the electrolyte-gated GFETs. In Fig. 1c, we demonstrated that the gate voltage dependent RF resistivity of graphene can be deduced (which is found to be consistent with its direct current (DC) counterpart in the full gate voltage range) even in the presence of the electrolyte which is in direct contact with the graphene layer. A time-dependent gating in solution with nanosecond time resolution, has also been demonstrate to access the potential of high-frequency sensing for real-time applications. We believe this work sets the ground for a novel RF approach to deeply probe biological pathways beyond the Debye screening length and has the potential to lead to groundbreaking changes in the field of biosensing.
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