Articles techniques et présentations

An ISFET is an ion-sensitive field effect transistor used to measure ion concentrations in a solution; when the ion concentration changes, the current through the transistor will change accordingly. Here, the solution is used as a gate electrode. A voltage between substrate and the oxide surfaces arises due to an ions sheath. The surface hydrolization of the OH groups of the gate materials varies in the aqueous solutions due to pH value. Typical gate materials are Si₃N₄, Al₂O₃, Ta₂O₅. Multiple microchannels of varying size are used to induce a potential on the floating gate. The microchannels (which act as multiple gates) can be arranged to cause flow of charge between the drain and the source of the MOSFET similar to a logic ‘and’ and logic ‘or’ operation.