The work function of palladium (Pd) is known to be sensitive to hydrogen (H2) via the formation of a surface dipole layer or Pd hydride. One approach to detect such a change in the work function is based on the formation of a Schottky barrier between Pd and a semiconductor. Here, we demonstrate a H2 sensor operable at room temperature by assembling solution-processed, pre-separated semiconducting single-walled carbon nanotube (SWNT) network bridged by Pd source/drain (S/D) electrodes in a configuration of field-effect transistors (FETs) with a local back-gate electrode. To begin with, we observed that the H2 response of the fabricated SWNT FETs can be enhanced in the linear operating regime, where the change in the work function of the Pd S/D electrodes by H2 can be effectively detected. We also explore the H2 responses in various SWNT FETs with different physical dimensions to optimize the sensing performance.
Carbon nanotubes (CNTs) have been regarded as a promising material for highly sensitive gas sensors due to their excellent material properties combined with their one-dimensional structural advantages, i.e., a high surface-to-volume ratio. Here we demonstrate a CNT-based gas sensor based on assembling highly purified, solution-processed 99.9% semiconducting CNT networks bridged by palladium source/drain electrodes in a field-effect transistor (FET) configuration with a local back-gate electrode. We investigated the gas responses of the CNT-FETs under different controlled operating regimes for the enhanced detection of H2 and NO2 gases using sensors with various physical dimensions. With the aid of the CNTs with high semiconducting purity (99.9%), we achieved excellent electrical properties and gas responses in the sensors and clearly determined that the operating regimes and physical dimensions of the sensors should be appropriately adjusted for enhanced sensing performance, depending on the gas molecules to be detected.
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