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Preparation of Silicon Nanowire Field-effect Transistor for Chemical and Biosensing Applications
Published on: April 21, 2016
True reference nanosensor realized with silicon nanowires
1Department of Physics, University of Basel, Basel, Switzerland. Alexey.Tarasov@unibas.ch
Langmuir : the ACS Journal of Surfaces and Colloids
|May 29, 2012
Summary
Researchers developed a novel reference field-effect transistor (FET) for electronic pH sensing. This reference FET significantly suppresses proton sensitivity, enabling more accurate measurements by effectively eliminating unwanted responses to pH changes.
Area of Science:
- Materials Science
- Nanotechnology
- Chemical Sensing
Background:
- Silicon field-effect transistors (FETs) with conventional gate oxides show promise for electronic pH sensing due to their active surfaces.
- Developing a stable reference electrode that senses electrostatic potential without responding to proton concentration remains a significant challenge in FET-based pH sensing.
- Existing nanowire FETs have advanced pH sensing capabilities but lack a true reference electrode.
Purpose of the Study:
- To demonstrate a highly effective reference sensor, termed a reference FET, with significantly suppressed proton sensitivity.
- To investigate the passivation of aluminum oxide (Al(2)O(3)) surfaces on nanowire FETs using self-assembled monolayers.
- To quantify the number of active proton binding sites during the passivation process.
Main Methods:
- Passivation of the Al(2)O(3) surface of a nanowire FET using a self-assembled monolayer of silanes with long alkyl chains.
- Utilizing a slow self-assembly process at 80 °C over several days to achieve full surface passivation.
- Quantitative comparison of measured nonlinear pH-sensitivities to a theoretical site-binding model to determine active proton binding sites over time.
Main Results:
- The developed reference FET exhibits a proton sensitivity suppressed by up to two orders of magnitude compared to conventional sensors.
- Full passivation of the Al(2)O(3) surface requires an extended self-assembly period of several days at 80 °C.
- Partially passivated surfaces demonstrate the ability to detect small changes in active proton binding sites, achieving a detection limit of approximately 170 μm(-2) Hz(-1/2) at 10 Hz and pH 3.
Conclusions:
- The reference FET design effectively suppresses proton sensitivity, offering a robust solution for stable electronic pH sensing.
- The study provides a method to quantify active proton binding sites by monitoring the passivation process over time.
- Partially passivated surfaces open avenues for sensitive detection of changes in surface binding sites in complex chemical environments.
