Electrical transport in some polymetallo phthalocyanines

Abstract

Complex ac impedance measurements on Poly metallo phthalocyanines before heat treatment (I[MPc]_n(M equals Cu, Ni)) have been performed and the data analyzed using the Havriliak-Negami dispersion relation for polymers. The parameters so obtained are reported. Heat treated polymers (II[MPc]_n (M equals Cu, Ni)) show an increase in dc electrical conductivity, (sigma) , by several orders of magnitude. The temperature dependence of (sigma) is in accordance with that expected for variable range hopping of carriers in 3 dimensions (VRH 3D) for II[CuPc]_n and that expected for VRH of carriers in 2D (VRH 2D) for II[NiPc]_n. The significant deviation from linearity of the log((sigma) (root)T) vs T^-1/4 plot at low temperatures can be accounted for by the model proposed by Sheng which is based on electron transfer across insulating gaps in conducting pathways by fluctuation induced tunneling. Hall mobility measurements of II[CuPc]_n show that the carriers are holes and the Hall constant was found to be 6 X 10^-4 (Omega) m/T at RT.