Conduction in partially monoclinic films of lead phthalocyanine

The X-ray diffraction pattern of vacuum sublimed thin films of lead phthalocyanine on glass substrates shows a partially monoclinic structure. The DC conduction is extrinsic since the activation energy is much smaller than the energy bandgap. AC conductivity sigma(ac) follows a power law dependence on frequency (f) for T less than or equal to 230K and 20Hz less than or equal to f less than or equal to 320kHz range, and this behaviour is believed to be due to correlated hopping of charge carriers over a reduced intercluster potential barrier of 0.49eV and a minimum distance of 6.7nm. Above 230K, the dielectric polarisation occurs due to structural inhomogeneities with a distribution of relaxation times. The conduction becomes independent of temperature at 1 MHz.