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ACS Sens. 2019 May 24;4(5):1197-1202. doi: 10.1021/acssensors.8b01366. Epub 2019 Apr 23.

Porous Nanophotonic Optomechanical Beams for Enhanced Mass Adsorption.

Author information

1
Nanotechnology Research Centre , National Research Council of Canada , Edmonton , Alberta T6G 2M9 , Canada.
2
Department of Physics , University of Alberta , Edmonton , Alberta T6G 2E1 , Canada.
3
Department of Biological Sciences , University of Alberta , Edmonton , Alberta T6G 2R3 , Canada.
4
Department of Computing Science , University of Alberta , Edmonton , Alberta T6G 2E8 , Canada.

Abstract

We have developed a porous silicon nanocantilever for a nano-optomechanical system (NOMS) with a universal sensing surface for enhanced sensitivity. Using electron beam lithography, we selectively applied a V2O5/HF stain etch to the mechanical elements while protecting the silicon-on-insulator photonic ring resonators. This simple, rapid, and electrodeless approach generates tunable device porosity simultaneously with the mechanical release step. By controlling the porous etchant concentration and etch time, the porous etch depth, resonant frequency, and the adsorption surface area could be precisely manipulated. Using this control, cantilever sensors ranging from nonporous to fully porous were fabricated and tested as gas-phase mass sensors of volatile organic compounds coming from a gas chromatography stream. The fully porous cantilever produced a dramatic 10-fold increase in sensing signal and a 6-fold improvement in limit of detection (LOD) compared to an otherwise identical nonporous cantilever. This signal improvement could be separated into mass responsivity increase and adsorption increase components. Allan deviation measurements indicate that a further 4-fold improvement in LOD could be expected upon speeding up characteristic peak response time from 1 s to 50 ms. These results show promise for performance enhancement in nanomechanical sensors for applications in gas sensing, gas chromatography, and mass spectrometry.

KEYWORDS:

NOMS; gas chromatography; gas sensing; mass sensing; porosity

PMID:
30942578
DOI:
10.1021/acssensors.8b01366

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