Research ArticleAPPLIED SCIENCES AND ENGINEERING

Silicon nanomembrane phototransistor flipped with multifunctional sensors toward smart digital dust

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Science Advances  01 May 2020:
Vol. 6, no. 18, eaaz6511
DOI: 10.1126/sciadv.aaz6511
  • Fig. 1 Structure and basic fundamental.

    (A) Schematic illustration of key functional layers of the smart sensor based on Si-NM in an exploded view. (B) Photograph of the fabricated smart sensor array. (C) Optical image of the sensitive area of the smart sensor. S, source; D, drain; G, gate. (D) Schematic illustration of the smart sensor array under illumination. (E) Schematic illustration of the mechanism in molecule detection. (F) Time-dependent performance of the smart sensor in hydrogen detection. Photo credits: Gongjin Li (Fudan University).

  • Fig. 2 Optoelectronic properties of the Si-NM phototransistor.

    (A) Drain current–gate voltage characterization under different irradiation intensity (405 nm) at a supply voltage (VDS) of 0.1 V. (B) Drain current–drain voltage characterization under different irradiation intensity (λ = 405 nm) at a gate voltage (VGS) of −3 V. (C) Linear response of the device at VDS = 1 V and VGS = −3 V. (D) Response time characterization of the device at VDS = 1 V and VGS = −3 V. The illumination power is ~0.3 mW/mm2.

  • Fig. 3 Bend resistance of the phototransistor.

    (A) The responsivity of the device after various bending cycles (VGS = −3 V and VDS = 0.1 V). Inset exhibits the bending state of the device in the test. Photo credit: Gongjin Li (Fudan University). (B) Electronic characters of the phototransistor (in dark) after various bending cycles (VGS = −3 V and VDS = 0.1 V).

  • Fig. 4 Performance of the smart sensor in the detection of hydrogen concentration and humidity measurement.

    (A) Transfer curves of the device at various hydrogen concentrations. The inset shows the characterization configuration in the experiment. The supply voltage VDS = 0.1 V. The intensity of 405-nm laser is ~0.8 mW/mm2. (B) Output curves of the smart sensor at various hydrogen concentrations. The gate bias VGS = −3 V. (C) Variation trend of the output signal (black squares; VGS = −3 V and VDS = 1 V) and transmittance of the Pd film (blue squares) with the increase of H2 concentration. (D) Transfer curves of the device at various relative humidities. The inset shows the characterization configuration in the experiment. The supply voltage VDS = 0.1 V. The intensity of 405-nm laser is ~0.8 mW/mm2. (E) Output curves of the smart sensor at various relative humidities. The gate bias VGS = −3 V. (F) Variation trend of the output signal (black squares; VGS = −3 V and VDS = 1 V) and transmittance of the hydrogel film (blue squares) with the increase of relative humidity. (G) Schematic illustration of the dual-channel sensing array on a single chip. The deep color film covered on the light-sensitive area is palladium, while the almost transparent one is hydrogel. (H) Optical image of the light-sensitive area (left) and (right) covered by both palladium and hydrogel smart materials. The upper and dark one is palladium membrane, and the lower and transparent one is the hydrogel film. Scale bars, 300 μm. (I) Drain current–gate voltage performance under different hydrogen condition (left) and relative humidity (right). Photo credits: Gongjin Li (Fudan University).

  • Fig. 5 Repeatability of relative humidity optoelectronic hydrogen concentration and relative humidity sensing capability.

    (A) Hydrogen sensing from low to high concentrations and then from high to low concentrations. The red line presents the low-to-high process, while the blue line presents the high-to-low process. (B) Multi-time tests of H2 concentration sensing. (C) Humidity measurement from low to high concentrations and then from high to low concentrations. The red line presents the low-to-high process, while the blue line presents the high-to-low process. (D) Multi-time tests of humidity sensing.

  • Fig. 6 Integrated system design.

    (A) Functional modules on the flexible smart system. (B) Complete system composed of the phototransistor array (optical image), amplifier, power supply, and logic units/memory for the humidity test in real time. (C) Time-dependent current output of the reference sensor (blank phototransistor; red dashed lines) and H2 sensor (blue dashed lines). Photo credit: Chunyu You (Fudan University). (D) Program flow chart of the smart system.

Supplementary Materials

  • Supplementary Materials

    Silicon nanomembrane phototransistor flipped with multifunctional sensors toward smart digital dust

    Gongjin Li, Zhe Ma, Chunyu You, Gaoshan Huang, Enming Song, Ruobing Pan, Hong Zhu, Jiaqi Xin, Borui Xu, Taeyoon Lee, Zhenghua An, Zengfeng Di, Yongfeng Mei

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