Effect of gamma irradiation on the optical properties of nano-MgPc thin films

Abstract

The thermal evaporation technique was used to deposit MgPc thin films. XRD and TEM studies were carried out for MgPc thin films. The effects of γ-radiation on the optical properties of MgPc thin films were characterized by using spectrophotometric measurements of the transmittance and reflectance in the spectral range from 200 nm to 2500 nm. The absorption spectra recorded in the UV-Vis region for as-deposited and radiated films showed two well-defined absorption bands of phthalocyanine molecule, namely the Q-band and the Soret (B) band. The Q-band showed its characteristic splitting (Davydov splitting) and ΔQ was obtained as 0.17 eV. The refractive index, n and the absorption index, k, were calculated. According to the analysis of dispersion curves, the parameters, namely; the dispersion energy (Ed), the oscillator energy (Eo) and the dielectric constant at infinite wavelength ε∞. Some of the important optical absorption parameters such as the molar extinction coefficient (εmolar), the oscillator strength, (f) and the electric dipole strength (q2) of the principle optical transitions were evaluated. The analysis of the spectral behaviour of the absorption coefficient (α), in the absorption region revealed indirect transitions. The optical and the onset respectively energy gaps were estimated as 2.74 and 1.33. Copyright © 2009 Inderscience Enterprises Ltd.