Silicon integrated microsensor incorporating a metal-doped phthalocyanine organic semiconductor used to selectively detect nitrogen dioxide and an organophosphorus compound

摘要

A novel gas-sensitive microsensor, whose design is based upon the interdigitated-gate-electrode field-effect transistor (IGEFET), was realieed by integrating it with a selectively-deposited, chemically-active, electron-beam evaporated copper phthalocyanine (CuPc) thin film. When isothermally operated at 150 °C the microsensor can selectively and reversibly detect parts-per-billion (ppb) concentration levels of two environmentally-sensitive pollutants -- nitrogen dioxide (NO{sub}2) and diisopropyl methylphos-phonate (DIMP). Although the CuPc thin film chemically and electrically interacts with NO{sub}2 and DIMP, just as it will likely interact with other electrically-active gases, or combinations thereof, the selectivity feature of the microsensor was established by operating it with a 5-V peak amplitude, 2-μs duration, 1000 Hz repetition frequency pulse, and then analyzing its time- and frequency-domain responses. As a direct consequence of this analysis, the envelopes associated with the normalized-difference Fourier transform magnitude frequency spectra reveal features which unambiguously distinguish the NO{sub}2 and DIMP challenge gas responses. Furthermore, the area beneath each response envelope may correspondingly be interpreted as a metric for the microsensor 5 sensitivity to a specific challenge gas concentration. Scanning electron microscopy (SEM) was used to characterize the CuPc thin film's morphology. Additionally, infrared (IR) spectroscopy was employed to verify the α- and β-phases of the sublimed CuPc thin films and to study the NO{sub}2- and DIMP-CuPc interactions.