Abstract: A metal-insulator-semiconductor diode sensor having a Pt/Ir alloy and/or a Pt/Sn alloy electrode is sensitive to and can detect ethylene. An array of metal-insulator-semiconductor diode sensors having varying sensitivity responses can indicate a fault in an electrical transformer by the detection of at least one of the key fault gases CO, H.sub.2, C.sub.2 H.sub.2 and C.sub.2 H.sub.4.

Abstract: A MIS diode sensor having a Pd/Cu alloy electrode is sensitive to and can detect CO, H.sub.2, C.sub.2 H.sub.2 and C.sub.2 H.sub.4. An array of MIS diode sensors having varying electrode compositions can indicate a fault in an electrical transformer by the detection of at least one of the key fault gases CO, H.sub.2, C.sub.2 H.sub.2 and C.sub.2 H.sub.4.

Abstract: A metal-insulator-semiconductor (MIS) diode having a suspended electrode forming a cavity between the electrode and the insulator is operated in the charge storage, i.e. inversion, mode to detect a fluid concentration. A reverse bias voltage is applied to the diode to form a charge inversion layer in the semiconductor, the bias is disconnected and subsequently reapplied. The charge that flows upon reapplication of the bias voltage is a measure of the concentration of a fluid in the cavity. An array of MIS diodes with multiplexed biasing and charge measurement permits detection of combinations of different fluids, even in the presence of potentially interfering chemical species.

Abstract: A detector and method for identifying a chemical vapor and determining its concentration in the ambient atmosphere. The chemical detector apparatus (120) preferably includes a plurality of surface acoustic wave (SAW) devices (10), each including a piezoelectric substrate (20), one-half (32) of which is coated with a selected polymer. The polymer characteristically absorbs one or more of a group of chemical vapors. Diffusion of a chemical vapor into the polymer increases its mass and proportionately changes the resonant frequency of the SAW device. A microcomputer control (186) is operative to determine a predicted time constant (or rate) for diffusion and a predicted equilibrium concentration of the chemical vapor within the polymer coating of the SAW device and to identify the chemical vapor and its relative concentration in the ambient atmosphere using the predicted values for these parameters long before the SAW device has reached equilibrium with the chemical vapor.

Abstract: Lightweight, compact apparatus for detecting sudden changes in the concentration of at least one selected gas provides a warning when said gas concentration increases suddenly. In one embodiment, a chemically sensitive field effect transistor provides a sensing signal two amplifiers having different overall gains and widely different time constants. Detection of sudden gas concentration changes causes the relative magnitudes of the amplifier output signals to be inverted triggering a warning. The apparatus may occupy less than 1.25 cubic inches and weigh less than 4 ounces so that it may be worn by an individual throughout his work place.

Abstract: The use of multiple field effect transistors, wherein only one transistor is sensitive to the presence of a particular element, is disclosed whereby similar responses to temperature and/or humidity fluctuations may be subtracted yielding a response to a particular element that is relatively insensitive to temperature and/or humidity variations.

Abstract: A method is disclosed for forming a chemically sensitive field-effect transistor having a suspended gate which enables the uniform and reproducible manufacture of such devices. Controlled uniformity and device response is provided by this method which makes the field-effect transistors suitable for use as sensors, alarms and analyzers for gases. A method of regenerating a chemically sensitive field-effect transistor having a suspended gate is also disclosed.

Abstract: A semiconductor photoelectrode resistant to photocorrosion and a method of preparing such a photoelectrode are disclosed. The photoelectrode includes a doped oxide layer on which illumination falls for photo-stimulation. The oxide layer is doped with metallic ions, such as tantalum ions, to suppress photocorrosion. In one oxide doping method, tantalum pentachloride vapor generated by sublimation is directed against a silicon dioxide layer on a heated photoelectrode.