Field-effect sensor for the selective detection of fluorocarbons

A chemical semiconductor sensor for the temperature range up to 400 degrees C was developed using silicon carbide with an epitaxial layer of SiC as th e substrate. Thin layers of LaF3 and Pt were deposited on the semiconductor /insulator structure to form a three-phase boundary with the gas under inve stigation. The sensor was shown to be sensitive to fluorine, hydrogen fluor ide and different fluorocarbons. The influence of the operation temperature on the sensor response signal was investigated in the range from room temp erature up to 400 degrees C. For the fluorocarbons CF3CH2F, CF3CCl3, CHClF2 , CF3CH2Cl and CCl3F a selective detection was achieved at temperatures nea r to 400 degrees C. The substantial rule of the fluoride ion conducting mat erial LaF3 for the sensor detection principle was proven. A mechanism inclu ding the chemisorption of the fluorocarbon at the Pt surface and an inserti on of fluorine into LaF3 was discussed. (C) 1999 Elsevier Science S.A. All rights reserved.