4.8 Article

Ultrasensitive N-Channel Graphene Gas Sensors by Nondestructive Molecular Doping

Journal

ACS NANO
Volume 16, Issue 2, Pages 2176-2187

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsnano.1c08186

Keywords

graphene; gas sensor; n-channel; gate-free; molecular doping; sensitivity

Funding

  1. Korea Institute for Advancement of Technology (KIAT) - Korea Government (MOTIE) [P0012770]
  2. Basic Science Research Program of the National Research Foundation of Korea (NRF) - Ministry of Science and ICT [2019R1A2C1010723]
  3. National Research Foundation of Korea [2019R1A2C1010723] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)

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Sensitive and selective detection of target gases is achieved using ultrasensitive n-channel graphene gas sensors doped with ethylene amines. The gas sensors demonstrate excellent response to oxidizing gases such as NO2, with a detection limit of 0.83 ppq. The sensors are fabricated on plastic without vertical stacks of gate-electrode and gate-dielectric, making them highly flexible and suitable for commercial use.
Sensitive and selective detection of target gases is the ultimate goal for commercialization of graphene gas sensors. Here, ultrasensitive n-channel graphene gas sensors were developed by using n-doped graphene with ethylene amines The exposure of the n-doped graphene to oxidizing gases such as NO 2 leads to a current decrease that depends strongly on the number of amine functional groups in various types of ethylene amines Graphene doped with diethylenetriamine (DETA) exhibits the highest response, recovery, and long-term sensing stability to NO2, with an average detection limit of 0.83 parts per quadrillion (ppq, 10(-15)), due to the attractive electrostatic interaction between electron-rich graphene and electron-deficient NO2. Our first-principles calculation supported a preferential adsorption of NO2 on n-doped graphene. In addition, gas molecules on the n-channel graphene provide charged impurities, thereby intensifying the current decrease for an excellent response to oxidizing gases such as NO2 or SO2. On the contrary, absence of such a strong interaction between NH3 and DETA-doped graphene and combined effects of current increase by n-doping and mobility decrease by charged impurities result in a completely no response to NH3. Because the n-channel is easily induced by a top-molecular dopant, a flexible graphene sensor with outstanding NO2 detection capability was successfully fabricated on plastic without vertical stacks of gate-electrode and gate-dielectric. Our gate-free graphene gas sensors enabled by nondestructive molecular ndoping could be used for the selective detection of subppq-level NO2 in a gas mixture with reducing gases.

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