IMPEDANCE SPECTROSCOPY APPLIED TO SEMICONDUCTING GAS SENSORS

By impedance spectroscopic measurements on gas sensors the real- and i maginary part of the resistivity is evaluated in the Frequency range o f 1 Hz to 1 MHZ. A detailed characterization is possible which provide s much more information about semiconducting gas sensors than the usua l d.c. resistivity measurement. Equivalent circuits describe formally different functional components of the sensor. This approach is used t o describe the gas interaction of the sensor by fit parameters of the impedance spectra. With this knowledge a systematic improvement of the design of the sensor is possible in view of achieving better selectiv ity, sensitivity and stability. This may be achieved by varying the co ntact geometry, dopants, structure of the sensitive layer, temperature and operation frequency.