Interdigitated gate electrode field effect transistor for the selective detection of nitrogen dioxide and diisopropyl methylphosphonate

Abstract

An Interdigitated gate electrode field effect transistor (IGE-FET) coupled to an electron beam evaporated copper phthalocyanlne thin film was used to selectively detect partper-billlon concentration levels of nitrogen dioxide (N02) and dlisopropyt methylphosphonate (DIMP). The sensor Is excited with a voltage pulse, and the timeand frequency-domain responses are measured. The envelopes of the magnitude of the normalized difference frequency spectrums reveal features that unambiguously distinguish NOz and DIMP exposures.

Interdigital sensors and transducers

“…A sensitive layer of an electron-beam evaporated copper phthalocyanine (CuPc) thin film has been used to detect part-per-billion concentration levels of nitrogen dioxide NO and diisopropyl methylphosphonate (DIMP) [85]. Another hygroscopic polymer, crosslinked cellulose acetate butyrate (CAB), has been used for humidity sensing [86].…”

“…The advantage of this approach is an intimate contact between the electrodes and the substrate, which in this case also serves as a sensitive layer [93]. An electron beam thermal evaporation process followed by a conventional mask etching allows control of both the deposition rate and the thickness of the films [77], [85]. Gold and platinum electrodes normally used in the electronics industry offer the advantage of being inert and flexible [94].…”

“…The guard electrodes are also known to be used to minimize stray surface leakage currents [85]. Our application did not require a guard ring covering the entire nonactive area of the substrate, because of the high surface resistance of the Teflon substrate under experimental conditions reported here.…”

“…A variety of interdigital sensors are used for a number of research and commercial applications to measure material properties [21], [117], control manufacturing processes [118], [119], monitor chemical and physical changes of fluid and solid dielectrics [79], [85], etc. In many cases, the interpretation of the sensor response depends on simple calibration procedures, yet in other cases, it requires sophisticated signal processing algorithms [120] and deep understanding of the physics and chemistry of the dynamic processes that are being monitored [121].…”

Analysis of Nitrogen Dioxide in Environment

“…Early work on FET gas sensors can be tracked back to 1980s. In a study by Kolesar et al [25] in 1989, IGE-FET was coupled to a thin film of copper phthalocyanine (CuPc), which selectively reacted with IGE-FET at ppb levels. Measurement was based on the sensitivity of the field effect transistor's output current to changes in the molecular structure or chemical composition of the thin film which covers the interdigitated gate electrode.…”