The ion-sensitive field-effect transistor (ISFET) is a new type of miniaturised semiconductor chemical sensor. It is based on the structure of the metal-insulator-semi-conductor field-effect transistor (MISFET) in which a metal gate is replaced by an ion selective membrane, an electrolyte and a reference electrode. In this paper, an ISFET is fabricated with silicon dioxide as a gate for a pH selective membrane. The measurement of pH sensitivity, selectivity and long-term characteristics of this device have been made. A pH sensitivity can be reached of 40 mV per pH. The oxide gate ISFET device has a significant response to K+ and Na+ ions even at the low concentration of 0.01 mol 1-1. The response to K+ ion is much higher than Na+ ion. The long-term stability of the silicon dioxide gate ISFET is also studied. The long-term drift is about 1 mV per hour after a ten hour immersion.
In this study, the (GeSbSn)(100-x0Co(x) films (x = 0-13.3) were deposited on natural oxidized silicon wafer and glass substrate by dc magnetron co-sputtering of GeSbSn and Co targets. The ZnS-SiO2 films were used as protective layers. The thicknesses of the (GeSbSn)(100-x)Co(x) films and protective layer were 100 nm and 30 nm, respectively. We investigated the effects of Co addition on the thermal property, crystallization kinetics, and crystallization mechanism of the GeSbSn recording film. The crystallization temperatures of (GeSbSn)(100-x)Co(x) films were decreased with Co content. It was found that the activation energy of the (GeSbSn)(100-x)Co(x) films will decrease from 1.53 eV to 0.55 eV as Co content increased from 0 at.% to 13.3 at.%.
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