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Gate coupling and carrier distribution in silicon nanowire/nanoribbon transistors operated in electrolyte
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
2011 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 29, no 1, 011022- p.Article in journal (Refereed) Published
Abstract [en]

The transfer characteristics of back-gate silicon nanowire/nanoribbon (NW/NR) transistors measured in electrolyte exhibit a significantly higher on-current and a steeper subthreshold behavior than measured in air. Simulation results show that the gate capacitance for a NW/NR of a trapezoidal cross-section immersed in water is significantly higher than that exposed to air. Electrostatics simulations further show that for NWs/NRs with small widths, carriers are mainly accumulated at the two side-edges when they are immersed in water. Even the top surface of the NWs/NRs sees more accumulated carriers than the bottom one does; the latter is in fact located closest to the back-gate. These observations suggest that the interface properties at the side-edges and the top surface are crucial for NW/NR transistors to achieve high sensitivity when performing real-time sensing experiments in electrolyte. Finally, the sensitivity of back-gate NW/NR field-effect transistors to charge changes in electrolyte is found to have a weak dependence on the NW/NR width when the doping concentration is below 10(17) cm(-3). For higher NW/NR doping concentrations, narrower NWs/NRs are more sensitive.

Place, publisher, year, edition, pages
2011. Vol. 29, no 1, 011022- p.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
URN: urn:nbn:se:uu:diva-149590DOI: 10.1116/1.3528215ISI: 000286648300024OAI: oai:DiVA.org:uu-149590DiVA: diva2:405124
Available from: 2011-03-21 Created: 2011-03-21 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Electronic Sensors Based on Nanostructured Field-Effect Devices
Open this publication in new window or tab >>Electronic Sensors Based on Nanostructured Field-Effect Devices
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Point-of-care (POC) diagnostics presents a giant market opportunity with profound societal impact. In particular, specific detection of DNA and protein markers can be essential for early diagnosis of e.g. cancer, cardiovascular disease, infections or allergies. Today, identification of these markers often requires extensive laboratory work and hence is expensive and time consuming. Current methods for recognition and detection of specific biomolecules are mostly optics based and thus impose severe limitations as to convenience, specificity, sensitivity, parallel processing and cost reduction.

Electronic sensors based on silicon nanowire field-effect transistors have been reported to be able to detect biomolecules with concentrations down to femtomolar (fM) level with high specificity. Although the reported capability needs further confirmation, the CMOS-compatible fabrication process of such sensors allows for low cost production and high density integration, which are favorable for POC applications. This thesis mainly focuses on the development of a multiplex detection platform based on silicon nanowire field-effect sensors integrated with a microfluidic system for liquid sample delivery. Extensive work was dedicated to developing a top-down fabrication process of the sensors as well as an effective passivation scheme. The operation mechanism and coupling efficiencies of different gate configurations were studied experimentally with the assistance of numerical simulation and equivalent circuits. Using pH sensing as a model system, large effort was devoted to identifying sources for false responses resulting from the instability of the inert-metal gate electrode. In addition, the drift mechanism of the sensor operating in electrolyte was addressed and a calibration model was proposed. Furthermore, protein detection experiments were performed using small-sized Affibody molecules as receptors on the gate insulator to tackle the Debye screening issue. Preliminary results showed that the directionality of the current changes in the sensors was in good agreement with the charge polarities of the proteins. Finally, a graphene-based capacitor was examined as an alternative to the nanowire device for field-effect ion sensing. Our initial attempts showed some attractive features of the capacitor sensor.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1018
Keyword
biosensor, field-effect transistor, nanowire, ISFET
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Nano Technology
Research subject
Electronics
Identifiers
urn:nbn:se:uu:diva-194015 (URN)978-91-554-8596-2 (ISBN)
Public defence
2013-03-27, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2013-03-05 Created: 2013-02-07 Last updated: 2013-04-02Bibliographically approved

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Chen, SiZhang, Shi-Li

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