New ISFET sensitive membranes

• Published in: Sensors and actuators. B, Chemical Chemical, 1990, Vol.1 (1), p.385-389
• Main Authors: Salardenne, J., Morcos, J., Aït Allal, M., Portier, J.
• Format: Article
• Language: English
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/0925-4005(90)80235-R

In the scope of detection of heavy ions (Pb ++, Cd ++, Sn ++,+++, Tl +, ...) in water we are looking for new versatile ISFET membranes. Chalcogenide and derived chalcohalide glasses are potentially interesting as membranes for selective electrodes or ISFET devices for the following reasons: low solubility in water, good ionic and very low electronic conductivities, wide range of composition permitting the preparation of various membranes. We present in this paper the study of a thin-film membrane for cadmium detection. The films have been prepared by r.f. magnetron sputtering from a target obtained by pressing under 1 T/cm 2 a powder mixture of composition 57As 2S 3 38Ag 2S 5CdS; the corresponding glass has already been used as a selective electrode (Y.G. Vlassov and E.A. Bychkov, Zh. Anal. Khim., 40 (8) (1986) 1438). The composition, structure and electrical properties of the films are studied. The C(V) response of Au/Si/SiO 2/membrane structures to Cd ++ concentration and pH in various solutions has been studied. Reproducible results are obtained in a buffer solution (Tris, pH 9) in the range of Cd ++ concentration of 10 −5 to 10 −2 mol 1 −1.