A chemically-selective microsensor for environmentally-sensitive pollutants realized with an interdigitated gate electrode field-effect transistor (IGEFET)

An IGEFET has been coupled with a chemically active, electron-beam evaporated copper phthalocyanine (CuPc) thin film to realize a gas-sensitive microsensor. The sensor can selectively detect parts-per-billion concentration levels of nitrogen dioxide (NO₂ ) and diisopropyl methylphosphonate (DIMP). The sensor is excited with a voltage pulse, and the time- and frequency-domain responses are measured. The envelopes associated with the normalized difference Fourier transform magnitude frequency spectra reveal features which unambiguously distinguish the NO₂ and DIMP challenge gas responses. The area beneath each response envelope can correspondingly be interpreted as the sensor´s sensitivity for a specific challenge gas concentration