Thickness and Annealing Effects on the Structural and Optical Conductivity Parameters of Zinc Phthalocyanine Thin Films

Abstract

In this work, the effects of the thin film thicknesses on the structural, optical absorption, energy band gap, dielectric spectra and optical conductivity parameters of the Zinc phthalocyanine thin films are considered. Thin films of ZnPc of thicknesses of 50-600 nm which are coated onto glass substrates are observed to exhibit amorphous nature of growth. The polycrystalline monoclinic ZnPc phase of the films is obtained via annealing the films at 200 degrees C in a vacuum atmosphere. Increasing the ZnPc films thickness shrunk the energy band gap in the B- and Q- bands and decreased both of the optical conductivities and free holes density in the Q-band. The increase in the film thickness is also observed to decrease the plasmon frequency and the drift mobility of holes in the films. The highest dielectric constant is obtained for films of thicknesses of 100 nm. The annealing process enhanced the optical absorption, redshifts the energy band gap value and the critical energy of the absolute maxima of dielectric constant. In addition, while the heat treatment enhanced both of the scattering times at femtosecond level and the drift mobility, it reduced the free holes density, and the plasmon frequency.