THIN-LAYER CHEMICAL SENSORS BASED ON CHEMICALLY DEPOSITED AND MODIFIED CHALCOGENIDE GLASSES

A new type of chemically deposited and modified thin-layer sensors has been prepared and investigated. Amorphous As2S3 and AsSe thin films o btained by the spin-coating technique and doped with silver were used as membrane materials of these sensors. It was found that the temperat ure of preliminary annealing of the films is crucial for doping effici ency. As-prepared films annealed above 120-degrees-C remain insulating after silver doping with subsequent annealing and/or light irradiatio n. XPS measurements indicated some kind of decomposition of arsenic ch alcogenides in this case. Properly prepared and modified thin layers a re mixed conductors with a final resistivity of about 10(5) OMEGA cm f or As2Se-based and almost-equal-to 10(3) OMEGA cm for AsSe-based films . Electrochemical measurements in AgNO3 solutions revealed a reasonabl e sensitivity of doped AsSe films to silver ions. The ionic response o f doped As2S3 films was found to be significantly poorer. High electro nic conductivity giving rise to competitive interfacial redox processe s seems to be one reason for such behaviour. The redox response of the films was studied in solutions of potassium hexacyanoferrate(II)/(III ) with total redox concentration from 0.1 to 0.001 M. The parameters o f the redox response of selenide glass thin-layer sensors are close to those of platinum electrode at high total redox concentration and eve n better in dilute solutions.