ENHANCEMENT OF THE NO2-SENSING CAPABILITY OF COPPER PHTHALOCYANINE BYMEASURING THE RELATIVE RESISTANCE CHANGE

The gas-sensing properties of copper phthalocyanine (CuPc) thin films have been measured for NO2 concentrations of 1 to 10 parts per million (ppm). The CuPc films thermally evaporated on glass substrates appear to have an cy-form polycrystalline structure. Most measurements of ga s sensitivity are done with heat-cleaned sensing elements to reduce th e instability of CuPc resistance. We have established unambiguously th at a significant enhancement of detectivity can be accomplished by con verting the resistance to a normalized figure, i.e., the relative resi stance. Good sensitivity to as low as 1 ppm has been reproducibly achi eved.