Research ArticleAPPLIED SCIENCES AND ENGINEERING

Room temperature multiplexed gas sensing using chemical-sensitive 3.5-nm-thin silicon transistors

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Science Advances  24 Mar 2017:
Vol. 3, no. 3, e1602557
DOI: 10.1126/sciadv.1602557
  • Fig. 1 Schematic illustrations and detailed images of a CS-FET chip.

    (A) Optical microscope image of a single CS-FET functionalized with a Pd-Au sensing layer integrated with microheaters. (B) Schematic illustration of a single-chip CS-FET array functionalized with different selective sensing layers. (C) Detailed zoomed-in representation of a single CS-FET. (D) Cross-sectional TEM image taken across the ultrathin silicon channel as shown in (C) with the associated EDS indicating the elemental composition of a single Pd-Au CS-FET. Scale bars, 250 μm.

  • Fig. 2 Sensing mechanism of CS-FETs.

    Schematic illustration of the band edge alignment across Pd-Au sensing layer and ultrathin silicon channel in a H2S-sensitive CS-FET (A) before H2S exposure and (B) after 100 ppb of H2S exposure. Evac, vacuum energy level; Ec, bottom of the silicon conduction band energy level; Ev, top of the silicon valence band energy level; Ef, silicon Fermi-level energy. (C) Experimental transfer characteristics (ID-VBG) of a H2S-sensitive CS-FET demonstrating Vt shift before and after 100-ppb H2S (in air) exposure (VDS = 10 mV). (D) Experimental output characteristics (ID-VDS) before and after 100 ppb of H2S (in air) exposure of the same CS-FET.

  • Fig. 3 Experimental characterization of individual CS-FETs.

    (A and B) Sensor response characteristics of a H2S-sensitive Pd-Au CS-FET (VDS = 100 mV; VBG = 0 V, relative humidity, ~30 to 40%; T ≈ 25°C). (C and D) Sensor response characteristics of a H2-sensitive Ni-Pd CS-FET (VDS = 2.5 mV; VBG = 0 V; relative humidity, ~30 to 40%; and T ≈ 25°C). (E and F) Sensor response characteristics of a NO2-sensitive Ni CS-FET (VDS = 2.5 mV; VBG = 0 V; relative humidity, ~45 to 50%; T ≈ 25°C).

  • Fig. 4 Multigas sensing using multiplexed CS-FETs.

    (A) Optical microscopy image of a single CS-FET array chip. Scale bar, 200 μm. (B) Real-time multiplexed sensing data to different gases (VDS = 25 mV; VBG = 0 V; relative humidity, ~40%; T ≈ 25°C). (C) Close-up snippets of individual detection events in (B).

  • Fig. 5 Aerial chemical sensing probes.

    (A) Image showing a microdrone equipped with a Ni-Pd–based H2-sensitive CS-FET (top) and an unassembled drone showing the individual components (bottom). DAQ, data acquisition. (B) Image depicting the experimental setup used for the aerial hydrogen sensing experiment. (C and D) Image capture of the CS-FET–equipped microdrone in motion at different times with corresponding altimetry and generated H2 sensor response, respectively.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/3/e1602557/DC1

    S1. Sensor characteristics of an unfunctionalized CS-FET sensor

    S2. Nanoparticle sensing layer sparsity analysis

    S3. Effect of silicon channel thickness on CS-FET sensitivity

    S4. CS-FET sensor response to temperature, relative humidity, and room temperature recovery characteristics

    S5. Individual sensor cycling from low and high gas concentrations

    S6. Fabrication process of chemical-sensitive 3.5-nm-thin silicon transistors

    S7. Microheater characterization

    S8. Transfer characteristics of H2S, H2, and NO2 CS-FETs

    fig. S1. Properties of a control CS-FET without any sensing film.

    fig. S2. Top-down TEM image of an ultrathin Pd0.3nmAu1nm on Si3N4 grids.

    fig. S3. CS-FET sensor response dependence on silicon channel thickness.

    fig. S4. Influence of ambient temperature and humidity on CS-FET sensor response.

    fig. S5. High-low-high gas concentration cycling of CS-FET sensors.

    fig. S6. CMOS-compatible fabrication process of CS-FETs.

    fig. S7. Integrated microheater material selection and characterization.

    fig. S8. Typical electrical transfer characteristics (ID-VBG) of functionalized CS-FETs.

  • Supplementary Materials

    This PDF file includes:

    • S1. Sensor characteristics of an unfunctionalized CS-FET sensor
    • S2. Nanoparticle sensing layer sparsity analysis
    • S3. Effect of silicon channel thickness on CS-FET sensitivity
    • S4. CS-FET sensor response to temperature, relative humidity, and room temperature recovery characteristics
    • S5. Individual sensor cycling from low and high gas concentrations
    • S6. Fabrication process of chemical-sensitive 3.5-nm-thin silicon transistors
    • S7. Microheater characterization
    • S8. Transfer characteristics of H2S, H2, and NO2 CS-FETs
    • fig. S1. Properties of a control CS-FET without any sensing film.
    • fig. S2. Top-down TEM image of an ultrathin Pd0.3nmAu1nm on Si3N4 grids.
    • fig. S3. CS-FET sensor response dependence on silicon channel thickness.
    • fig. S4. Influence of ambient temperature and humidity on CS-FET sensor response.
    • fig. S5. High-low-high gas concentration cycling of CS-FET sensors.
    • fig. S6. CMOS-compatible fabrication process of CS-FETs.
    • fig. S7. Integrated microheater material selection and characterization.
    • fig. S8. Typical electrical transfer characteristics (ID-VBG) of functionalized CS-FETs.

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