Contact between two oxide semiconductor grains different in work function (hetero-contact) is characterized by the generation of contact potential, which is sensitive to gases. The resistance of the hetero-contact is influenced by ambient gases dually, through a change in the surface density of carriers (receptor function of key grain) and through a change in drift mobility of electrons (contact potential effect), and hence not only it is more sensitive to gases than that of contact between grains of the same kind (homo-contact) but also it obeys different power laws. It is shown through explorations using device models that a novel composite oxides gas sensor making use of contact potential will be available if the two kinds of grains to be combined are selected properly and the structure the grains are packed in is designed properly. It is especially important to achieve such particular packing structure that allows hetero-contacts to be included in the main paths of electron transport.
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