INTERACTION OF NO2 WITH COPPER PHTHALOCYANINE THIN-FILMS .1. CHARACTERIZATION OF THE COPPER PHTHALOCYANINE FILMS

Thin films of copper phthalocyanine (CuPc) have been deposited by vacuum evaporation on glass or alumina substrates maintained at different temperatures. The morphology and the crystallinity of as-deposited films and of heat-treated and/or NO2-treated films have been studied by electron microscopy and X-ray diffraction. The crystallinity of the films increases with substrate temperature during deposition: films deposited at room temperature or below are. rather amorphous, whereas films deposited at 80-degrees-C or 200-degrees-C exhibit a highly uniaxial order of their crystallites; this order is altered by heat treatment or NO2 doping. Scanning electron microscopy shows that the morphology of the film surface also depends on deposition temperature and that heat treatments induce the growth of whiskers from the surface. The structural changes are also observed through the temperatures of maximum conductivity of the CuPc films doped with NO2. The sensitivity of CuPc to NO2 could be applied to gas sensing.