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Electronic Sensors Based on Nanostructured Field-Effect Devices
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. (emerging electronics)
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 [en]
biosensor, field-effect transistor, nanowire, ISFET
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Nano Technology
Research subject
Electronics
Identifiers
URN: urn:nbn:se:uu:diva-194015ISBN: 978-91-554-8596-2 (print)OAI: oai:DiVA.org:uu-194015DiVA: diva2:603888
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
List of papers
1. Gate coupling and carrier distribution in silicon nanowire/nanoribbon transistors operated in electrolyte
Open this publication in new window or tab >>Gate coupling and carrier distribution in silicon nanowire/nanoribbon transistors operated in electrolyte
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.

National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-149590 (URN)10.1116/1.3528215 (DOI)000286648300024 ()
Available from: 2011-03-21 Created: 2011-03-21 Last updated: 2017-12-11Bibliographically approved
2. Contacting versus Insulated Gate Electrode for Si Nanoribbon Field-Effect Sensors Operating in Electrolyte
Open this publication in new window or tab >>Contacting versus Insulated Gate Electrode for Si Nanoribbon Field-Effect Sensors Operating in Electrolyte
2011 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 24, 9546-9551 p.Article in journal (Refereed) Published
Abstract [en]

Electric response to pH variations is employed to investigate Si nanoribbon field-effect transistors (SiNRFETs) operating in electrolyte with different gate configurations. For devices with a concluding gate electrode for direct metal electrolyte contact, a well-defined electrode reaction leading to a stable electrode potential is essential for retaining a stable electrical potential of the electrolyte. However, noble metals such as Pt do not meet the stability requirement and consequently bring severe distortions to the electronic response. For devices with an insulated gate electrode relying on the principle of capacitive gate coupling, the capacitance between the gate electrode and the electrolyte should be made much larger than the gate capacitance established between the SiNR and the electrolyte. In this case, an efficient gate control as well as a high stability against external disturbances can be ensured. Further studies show that surface charging of the gate insulator is the main cause responsible for the pH response of the SiNRFETs. Hence, devices with different gate configurations give rise to a comparable pH sensitivity.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-164117 (URN)10.1021/ac2023316 (DOI)000297946900053 ()
Available from: 2011-12-16 Created: 2011-12-16 Last updated: 2017-12-08Bibliographically approved
3. Current Instability for Silicon Nanowire Field-Effect Sensors Operating in Electrolyte with Platinum Gate Electrodes
Open this publication in new window or tab >>Current Instability for Silicon Nanowire Field-Effect Sensors Operating in Electrolyte with Platinum Gate Electrodes
Show others...
2011 (English)In: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 14, no 7, J34-J37 p.Article in journal (Refereed) Published
Abstract [en]

Current instability is observed for silicon nanowire field-effect transistors operating in electrolytes with Pt gate electrodes. A comparative study involving an Ag/AgCl-reference gate electrode reveals that the effect results from a drift in the potential at the Pt-electrode/electrolyte interface. In a phosphate buffer saline of pH 7.4, the stabilization of the potential of the Pt electrode was found to require approximately 1000 s. A concurrent potential drift, with a comparable time constant, occurring at the electrolyte/oxidized-nanowire interface rendered a complex device current response which complicated the interpretation of the results.

National Category
Engineering and Technology Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry; Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-154111 (URN)10.1149/1.3584082 (DOI)000290276400027 ()
Available from: 2011-05-26 Created: 2011-05-26 Last updated: 2017-12-11Bibliographically approved
4. A two-terminal silicon nanoribbon field-effect pH sensor
Open this publication in new window or tab >>A two-terminal silicon nanoribbon field-effect pH sensor
Show others...
2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 26, 264102- p.Article in journal (Refereed) Published
Abstract [en]

This paper reports on a two-terminal silicon nanoribbon (SiNR) field-effect pH sensor operated in electrolyte. Observed experimentally and confirmed by modeling, the sensor is activated by self-gating with a gate bias set by the potential difference of the two terminals. The effect of this gate bias on the SiNR conductance is modulated by the potential drop over the electrical double layer (EDL) established on the SiNR surface, similarly to the threshold voltage modulation by EDL in a three-terminal SiNR field-effect transistor with an independent gate electrode. The potential drop over EDL is determined by the pH value of the electrolyte.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-139888 (URN)10.1063/1.3532964 (DOI)000285768100095 ()
Available from: 2010-12-30 Created: 2010-12-30 Last updated: 2017-12-11Bibliographically approved
5. A graphene field-effect capacitor sensor in electrolyte
Open this publication in new window or tab >>A graphene field-effect capacitor sensor in electrolyte
Show others...
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 15, 154106- p.Article in journal, Letter (Refereed) Published
Abstract [en]

The unique electronic properties of graphene are exploited for field-effect sensing in both capacitor and transistor modes when operating the sensor device in electrolyte. The device is fabricated using large-area graphene thin films prepared by means of layer-by-layer stacking. Although essentially the same device, its operation in the capacitor mode is found to yield more information than in the transistor mode. The capacitor sensor can simultaneously detect the variations of surface potential and electrical-double-layer capacitance at the graphene/electrolyte interface when altering the ion concentration. The capacitor-mode operation further facilitates studies of the molecular binding-adsorption kinetics by monitoring the capacitance transient

National Category
Electrical Engineering, Electronic Engineering, Information Engineering Nano Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-185550 (URN)10.1063/1.4759147 (DOI)000310304900106 ()
Available from: 2012-11-26 Created: 2012-11-26 Last updated: 2017-12-07

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