Binary Gas Mixture Analysis with an Interdigitated Gate Electrode Field Effect Transistor (IGEFET) Microsensor

Single component and binary gas mixtures of nitrogen dioxide (NO2) and ammonia (NH3) were analyzed with a microsensor composed of an array of interdigitated Gate Electrode Field Effect Transistor (IGEFET) sensor elements coated with copper-, nickel-, and cobalt-phthalocyanine thin films. Improvements in the IGEFET microsensor design and operation facilitated simultaneous measurement of ihe direct current (DC) and alternating current (AC) electrical response of the metal-substituted phthalocyanine (MPc) films to challenge gas exposure. A finite-difference model of the interdigitated gate electrode (IGE) structure confirmed the fundamental operation of the IGEFET microsensor. Principal component analysis (PCA) and multilinear regression were applied to features identified in the IGE structure's normalized DC resistance response, as well as the IGEFET transfer function's gain and phase response, to gas mixtures containing parts-per-billion (ppb) NO2 and parts-per-million (ppm) NH3. The predicted concentrations were generally within 50% of the known concentrations for all gas analyses. The single component analysis of each test gas using the normalized DC resistance data yielded the smallest error (14% for NH3 and 26% for NO2). For the binary gas mixture analysis, the smallest error was achieved with the gain response data (approximately 25% for each component). jg p63