Engineering and Architecture
Technologies for Nanosystems, Bioengineering and Energy
High Frequency FETs for gas sensing
The project will focus on the characterization from DC to hundreds of GHz of high frequency Field Effect Transistor (HF-FET) of Two Dimensional (2D) nanomaterials and be able to test its performance as microwave gas sensor. This project will support the advance of research for nanotechnology application, achieving highly sensitive and selective miniaturized gas sensors, and the integration of sensors in wireless systems. Until now, chemoresistors (i.e., resistive gas sensors) employing metal oxides as gas sensitive films have been the most successfully marketed inexpensive devices. Chemoresistors are simple in layout, easy to operate and can be miniaturized. In addition, metal oxides are highly sensitive to a wide spectrum of gases of interest. Despite all these advantages, they generally require being operated high above room temperature (power-hungry), show poor selectivity and suffer from long-term stability issues. Therefore, metal oxide chemoresistors are not well suited for being integrated into a new generation of 5G enabled IoT devices and unattended gas sensing networks.
The development of wireless networks with higher amounts of data transferred at higher speeds is fueling the research in a new generation of high frequency electronics such as high frequency field effect transistors HF-FET employing new nanomaterials.
Among the already existing gas sensing platforms, field effect transistors (FETs) are very attractive due to their simple fabrication process, sensitive gas detection and easy miniaturization down to the nanoscale. Field Effect Transistor gas sensors can become an alternative and superior sensing platform to the current chemoresistors. FET gas sensors can be miniaturized down to the nanoscale and fabricated at low costs employing microsystems technologies. Upon exposure to gas molecules and adsorption of these at the channel area, the electronic structure is altered, which can be exploited for gas sensing. For example, gas adsorption results in the doping of the semiconductor material at the channel, altering the concentration and mobility of charge carriers; gas adsorption may lead to the formation of dipoles at the surface of the channel, which affects the threshold voltage. Gas detection can be as simple as measuring the change of the drain current after exposing the FET to a target gas under constant drain to source and gate to source voltages. The evolution of FET gas sensors has been closely related to the evolution of nanotechnology and, very particularly to research in two-dimensional (2D) materials [1,2].
Since the discovery of graphene in 2004, with the first isolation of graphene nanosheets by mechanical exfoliation of graphite , the research in 2D-materials has been attracting increasing interest. The extraordinary properties of graphene have opened new perspectives to other 2D-materials such as transition metal dichalcogenides (TMD), black phosphorus (BP), hexagonal boron nitride (h-BN) and others. While graphene is a zero-bandgap semiconductor, black phosphorus and TMD monolayers like MoS2, WS2, WSe2, are direct band gap semiconductors and h-BN is an interesting insulator for device passivation. Many chalcogenides such as ZrS2, InSe, PtSe2, only to cite a few, have been seldom studied. All these nanomaterials present large surface to volume ratios and outstanding electrical (tunable band gap, high carrier mobility, high on/off current ratio, electrical anisotropy), optical (absorption in the visible and infra-red, thermal, mechanical and chemical properties, the exploitation of which shows high potential for developing a new generation of low-power gas nanosensors with high sensitivity, short response and recovery times, low detection limit, high selectivity and good stability [4,5].
High frequency field effect transistors (HF-FETs) employing 2D materials are key for the advancement of the new generation of wireless technology and sensing systems. The performance of a HF-FET is represented by its figure of merit (FoM): the cut off frequency (ft) and the maximum oscillation frequency (fmax). ft is the frequency at which current gain (h21) drops to unity (0 dB) and fmax is the frequency at which the unilateral power gain (U) equals unity. In particular, for frequencies lower than ft, the transistor is able to provide current gains h21 larger than unity. Extrinsic ft and fmax depend on the quality of the materials employed during the fabrication process, the choice of the dielectric of the substrate and under the gate electrode. New study will be hold to evaluate the FoM of our 2D HF-FET under various gas excitation [6,7].
The applicant should be highly motivated to develop new set up. It’s recommended to have solid background in electrical engineering and high frequency characterization. The successful candidate will be initiated to the synthesis and the nanocharacterization of novel nanomaterials. He/she will actively participate to the development of high frequency system of measurement using Vector Network Analyzer VNA and the characterization of high frequency FET gas sensor
 Tyagi, D.; Wang, H.; Huang, W.; Hu, L.; Tang, Y.; Guo, Z.; Ouyang, Z. & Zhang, H. Nanoscale, Royal Society of Chemistry (RSC), 2020, 12, 3535-3559.
 Yang, S.; Jiang, C. & Wei, S.-h. AIP Publishing, 2017, 4, 021304
 Novoselov, K. S. Science, American Association for the Advancement of Science (AAAS), 2004, 306, 666-669
 Llobet, E.Sensors and Actuators B: Chemical, Elsevier BV, 2013, 179, 32-45
 Buscema, M.; Groenendijk, D. J.; Blanter, S. I.; Steele, G. A.; van der Zant, H. S. J. & Castellanos-Gomez. Nano Letters, American Chemical Society (ACS), 2014, 14, 3347-3352
 Fadil, D.; Wei, W.; Deng, M.; Fregonese, S.; Strupinski, W.; Pallecchi, E. & Happy, H. IEEE/MTT-S International Microwave Symposium - IMS, IEEE, 2018
 Zhu, L.; Farhat, M.; Salama, K. N. & Chen, P.-Y. Emerging 2D Materials and Devices for the Internet of Things, Elsevier, 2020, 29-57
Highly desirable attributes of the ideal candidate
* Demonstrated previous experience in one or some of the following topics: Use of clean room facilities, bottom up or top down synthesis of nanomaterials, electronic poroperties of materials, high frequency electronics
* Hold a Master degree, or equivalent, in: Electronics Engineering, Physics, Nanotechnology
* Language skills: English
* Specific Software skills: none
* Other skills: Good coomunication skills, able to work in a team, able to meet deadlines,
* Personality traits: Responsible, proactive, ready to help other team members
Ethics: This project doesn’t involve ethical aspects
Workplace Location: Campus Sescelades, Tarragona
37.5 hours a week
14 February 2022
|This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 945413|