Metrology and Measurement Systems

Abstract

Alternating current a.c. measurements enable to understand the physical and chemical processes occurring in semiconductor materials. Impedance spectroscopy has been successfully applied to study the responses of gas sensors based on metal oxides, such as TiO 2 , SnO 2 and TiO 2 /SnO 2 nanocomposites. This work is devoted to dynamic measurements of hydrogen sensor behaviour over the temperature range of 300-450 • C. Frequency dependence of the impedance signal gives evidence that 50 mol% TiO 2 /50 mol% SnO 2 nanocomposites should be treated as resistive-type sensors. Temporal evolution of the response to 500 ppm H 2 at 320 • C indicates a very short response time and much longer recovery.