Copper-doped vacuum evaporated chalcogenide layers as sensitive ion-selective membranes

The possibilities of using photodoped chalcogenide layers evaporated on standard Si/SiO 2/Si 3N 4 substrates as Cu ion sensitive membranes for ion selective field-effect transistors (ISFETs) are investigated. The optimal concentrations of the doped metals (Cu, Ag) are determined providing linearity of some properties at concentrations 10 −1–10 −6 M. The membrane samples show a selectivity in the presence of Na, less in the presence of Fe, Zn, Pb, Cr and lack of selectivity to Ag. The depth distribution of Cu and Ag in chalcogenide layer is measured by atomic electron spectroscopy. The effect of the depth profiles of the dopants on the electrochemical properties of the Si/SiO 2/Si 3N 4/Cr/Cu x Ag y (As 2S 3) 100−( x+ y) membranes are measured. The results obtained indicate that ISFETs are possible.