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An ion-gated bipolar amplifier for ion sensing with enhanced signal and improved noise performance
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2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal, Letter (Refereed) Published
Place, publisher, year, edition, pages
2014.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-235235OAI: oai:DiVA.org:uu-235235DiVA: diva2:759472
Available from: 2014-10-30 Created: 2014-10-30 Last updated: 2017-12-05
In thesis
1. On the Low Frequency Noise in Ion Sensing
Open this publication in new window or tab >>On the Low Frequency Noise in Ion Sensing
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ion sensing represents a grand research challenge. It finds a vast variety of applications in, e.g., gas sensing for domestic gases and ion detection in electrolytes for chemical-biological-medical monitoring. Semiconductor genome sequencing exemplifies a revolutionary application of the latter. For such sensing applications, the signal mostly spans in the low frequency regime. Therefore, low-frequency noise (LFN) present in the same frequency domain places a limit on the minimum detectable variation of the sensing signal and constitutes a major research and development objective of ion sensing devices. This thesis focuses on understanding LFN in ion sensing based on both experimental and theoretical studies.

The thesis starts with demonstrating a novel device concept, i.e., ion-gated bipolar amplifier (IGBA), aiming at boosting the signal for mitigating the interference by external noise. An IGBA device consists of a modified ion-sensitive field-effect transistors (ISFET) intimately integrated with a bipolar junction transistor as the internal current amplifier with an achieved internal amplification of 70. The efficacy of IGBA in suppressing the external interference is clearly demonstrated by comparing its noise performance to that of the ISFET counterpart.

Among the various noise sources of an ISFET, the solid/liquid interfacial noise is poorly studied. A differential microelectrode cell is developed for characterizing this noise component by employing potentiometry and electrochemical impedance spectroscopy. With the cell, the measured noise of the TiN/electrolyte interface is found to be of thermal nature. The interfacial noise is further found to be comparable or larger than that of the state-of-the-art MOSFETs. Therefore, its influence cannot be overlooked for design of future ion sensors.

To understand the solid/liquid interfacial noise, an electrochemical impedance model is developed based on the dynamic site-binding reactions of surface hydrogen ions with surface OH groups. The model incorporates both thermodynamic and kinetic properties of the binding reactions. By considering the distributed nature of the reaction energy barriers, the model can interpret the interfacial impedance with a constant-phase-element behavior. Since the model directly correlates the interfacial noise to the properties of the sensing surface, the dependencies of noise on the reaction rate constants and binding site density are systematically investigated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1519
Keyword
low frequency noise, ion sensor, ISFET, electrochemical impedance spectroscopy, constant phase element, surface chemistry, CMOS technology
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Nano Technology Physical Chemistry
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-320544 (URN)978-91-554-9919-8 (ISBN)
Public defence
2017-06-09, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-05-17 Created: 2017-04-21 Last updated: 2017-06-07

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