Surface State Model for Metal Oxide p-Type Conductometric CO Sensors

The materials exploited for the development of gas conductometric sensors are often n-type semiconductors as in the case, e.g., of SnO2. Several materials studied in the last years for this application behave as p-type semiconductors (e.g. CuO, Cr2O3, K- or Ag-Hollandites). In this work the authors present a novel surface state model for p-type, large grained, thick film materials, with a specific reference to K- or Ag-Hollandites, which accounts for the material response to CO in dry and humid N-2, and in dry and humid air. A reliable and compact model of this type is of the utmost utility from several points of view, including the development of measurement systems based on gas sensors. The availability of a simulation tool able to accurately predict the sensor behavior enables the replacement of experimental tuning with simulations, and can significantly speed-up sensor-based system development and guarantee better performance.