Thermal annealing effect on the structural and optical characteristics of silicon phthalocyanine dichloride thin films

Abstract

The crystal structure of silicon phthalocyanine dichloride (SiPcCl2) was studied using X-ray diffraction (XRD). The SiPcCl2 powder was polycrystalline and transformed to an amorphous form for pristine and annealed thin films. The prepared films were annealed at 363 K, 403 K, 543 K and 493 K for 2 h in a drying oven. The optical characteristics of these films were studied under normal light incidence in wavelength range from 190 to 2500 nm using spectrophotometry technique. The electronic transition type is an indirect allowed transition with optical and onset energy gaps of 1.92 eV and 1.25 eV, respectively. As the temperature rised, the defects gradually disappeared and the localized density of states tended to decrease; thus, the optical energy gap increased. The annealing effect on optical parameters, such as the real (ε1) and imaginary (ε2) parts of the dielectric constant, the volume energy loss function (VELF) and the surface energy loss function (SELF), was studied. The ratio between the free charge carrier concentration and the effective mass (N/m*), the lattice dielectric constant (εL), the infinite frequency dielectric constant (ε∞), the oscillator energy (Eo) and the dispersion energy (Ed) were calculated before and after thermal annealing.