Electrical Properties of Bromine-Doped Nickel (Phthalocyanine) Films and Their Structural Change

Abstract

The change in electrical conductivity of bromine-doped nickel phthalocyanine (Ni(Pc)) film doping level has been studied based upon the analysis of the film structure. The electrical conductivity of bromine-doped Ni(Pc) films exhibits a maximum and minimum at doping levels x (=Br/Ni)≃ 1 and 4, respectively. Its apparent activation energy also shows a minimum and maximum, which respectively correspond to the maximum and minimum of the electrical conductivity. It was concluded that the decrease in conduction accompanied by the decrease in activation energy with doping level in the range (1< x <4) arises from the decrements in both the number of electrical conduction paths and charge carriers due to cracks on the film surface, and from the morphological change from polycrystalline into amorphous structures. It is, however, uncertain why the electrical conductivity again increases above x ≃4.