Organic molecular thin films as gas sensors

In this paper we will present some interesting data on the gas sensitivity of very thin films of metal phthalocyanine (as copper phthalocyanine, CuPc) towards NO₂ at very low concentration (ppb). A thermal treatment following the deposition strongly enhances the gas sensitivity. We will relate this high gas sensitivity to the surface morphology of the film. In fact atomic force microscopy data indicate that after the thermal treatment the surface roughness strongly increases, while the crystalline structure, which is less influenced by the thermal process, gives a lower contribution to the gas sensing properties.