HIGHLY SENSITIVE NO2 SENSOR DEVICE FEATURING A JFET-LIKE TRANSDUCER MECHANISM

The conductance of a thin SnO2 him in contact with platinum is used to detect NO2 down to the 10 ppb range with a cross sensitivity to CO of the order of only 10(-4). The SnO2 layer thickness of 60 nm is chosen of the order of the depletion layer caused by the action of adsorbed oxygen ions and by the Schottky contact at the platinum interface. By a strong sintering pretreatment potential barriers between the grains are avoided and a diffusion of the ambient gas into the layer is suppr essed. The width of the conductive channel in the middle of the SnO2 l ayer is reduced in the presence of NO, adsorbed on the surface. This s trongly electrophilic molecule forms acceptor surface states energetic ally below the acceptor states of the adsorbed oxygen thus enhancing t he electron depletion. (C) 1998 Elsevier Science S.A. All rights reser ved.