Gas sensitive properties of copperphthalocyanine thin films

Copperphthalocyanine (CuPc) thin films, about 250 nm thick, were prepared by vacuum evaporation on glass substrates, and their gas sensitive properties were examined. Two kinds of CuPc films, polycrystalline and amorphous, were obtained by changing the substrate temperature. A pair of Au electrodes were vacuum deposited on the CuPc films, and the conductivity change associated with introduction of NO2 gas into the measuring chamber was measured. The conductivity increased by several orders of magnitude associated with introduction of NO2 gas (1000 ppm) for both the specimens at room temperature. The gas sensitivity of the amorphous CuPc film was higher than that of the polycrystalline film. This result was attributed to the fact that stacking of CuPc molecules was more loose in the amorphous film than in the polycrystalline film. The gas sensitivity and the response were found to be improved with light irradiation.