Quantification and effects of molecular oxygen and water in zinc phthalocyanine layers

Gas effusion measurements on zinc phthalocyanine (ZnPc) layers showed the p resence of a significant amount of oxygen and water inside the material dur ing exposure to ambient conditions. Of both species the bulk concentration lay in the range of 10(20) molecules per cm(3). Temperature-dependent analy sis indicated that at 296 K all O-2 molecules, and roughly one half of the H2O molecules, were mobilized and diffused with diffusion coefficients D-O2 of 3 * 10(-8) cm(2)/s and D-H2O of 1.3 * 10(-10) cm(2)/s. Electrical analy sis of ZnPc layers in controlled atmospheres revealed that the electrical p roperties of the bulk were determined by O-2, whereas H2O influences the su rface conductivity. A space-charge density of (1.6 +/- 0.2) * 10(16) O-2(-) ions per cm(3) was measured in atmospheric conditions.