Emi, LLC

Thorn Emi Plc

Sharp Kabushiki Kaisha Corporation

Brian C Webb

John F Ross

Ian Robins

Masaya Hijikigawa

Alastair Sibbald

Hisatoshi Furubayashi

John Edward Shaw

Derek G Pedley

Edward C Bell

Stephen J Prosser

A method of making a humidity sensor comprises providing a host device constituted by a semi-conductor substrate (10) and a gate insulator (13) of an insulated gate field effect transistor, forming a layer (14) of poly (vinyl) alcohol (PVA) on the exposed surface of the insulator, heat treating the layer to crystallize and stabilize the PVA, and forming a gate electrode (15) on the PVA layer, so that the gate electrode is porous allowing ambient water vapor to be absorbed by the PVA which, in response, undergoes a change of bulk dielectric constant, thereby causing a change in gate capacitance of the transistor resulting in a detectable change of electrical conductivity in the drain source channel.

Humidity sensor

A gas sensitive device, for example a gas sensitive MISFET (FIGS. 1 to 3) has a gas-sensitive electrode (15) comprising a catalytically active metal (e.g. Pt or Pd) and a non-metallic material (e.g. SiO.sub.2) mixed with, or deposited at an exposed surface of, the metal to modify the catalytic activity of the metal. The electrode has an enhanced sensitivity to, and selectivity of, certain gases. The composite material is applicable to other gas-sensitive devices, e.g. an optical fibre gas sensor.

Gas sensitive device

An ionic conductivity accelerometer comprises a layer of an ionically conductive material such as rubidium silver iodide (RbAg.sub.4 I.sub.5) deposited on an electrically insulative substrate with spaced electrodes in contact with the layer. The ionically conductive material may be mixed with an electrically insulative, chemically inert material such as quartz wool in order to alleviate susceptibility to cracking.

Ionic conductivity accelerometer

An ammonia gas sensor comprises a dual gate field effect transistor (FET) in which the two gate electrodes are of platinum deposited respectively by sputtering and evaporation. The gate regions of the two FETs are connected together differentially and the net drain source voltage represents the concentration of ammonia gas to which the sensor is exposed.

Gas sensor

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Sunbury, United Kingdom

Brian C Webb