Ellipsometric Studies of Polyaniline-Effective Dimension of “Conducting”States

A model of fractional-dimensional space is employed to study the measured ellipsometric spectra of polyaniline with acid doping treatment. Aside from some band parameters, the important dimensional properties of electronic states in the system associated with direct interband transitions can be obtained. The results indicate that as doping density is increased, the effective dimension (D) of electron states in the polyaniline changes from about 1.5D t o near 2.6D, in the same time the polyaniline shows an insulator-metal transition. A brief discussion about the results is given.