Effects of γ-ray irradiation and thermal annealing on structural, optical and electrical properties of vacuum deposited vanadyl 2,3-naphthalocyanine thin films

Vacuum deposited vanadyl naphthalocyanine (VONc) crystalline thin films were produced. The films showed a completely different structural and growth pattern on thermal annealing and γ-ray irradiation. The XRD spectra revealed polycrystalline nature for both annealed and γ-ray irradiated films. Raman spectra observes that the γ-irradiated films had a higher disorder producing broad and diffuse peaks in comparison to its annealed samples. In the absorption spectra, the γ-irradiated films shows a broad Q-band with a shift of 50 nm towards the IR region enabling VONc to be used in a lot of applications using the commercially available semiconductor NIR lasers. Films on 97.9 krad γ-ray irradiation showed some interesting properties with a better conductivity compared to either it’s higher γ-ray irradiated counterpart (195.8 krad) or the annealed films. Also the activation energy values, which is the minimum amount of energy required to liberate charge carriers from traps or to ionize levels within the band gap, was found to be lowered to half of its value for the films irradiated at 97.9 krad promising its performance in optical data recording, photo-sensitizer in photodynamic therapy, etc.