Abstract
Para-quaterphenyl thin films were deposited onto glass and quartz substrates by thermal evaporation method. p-quaterphenyl thin films wereexposed to gamma radiation of Cobat-60 radioactive source at room temperature with a dose of 50 kGy to study the effect of ?-irradiation onthe structure and the surface morphology as well as the optical properties of the prepared films. The crystalline structure and the surface morphology of the as-deposited and ?-irradiated films were examined using the X-ray diffraction and the field emission scanning electron microscope. The optical constants (n & k) of the as-deposited and ?-irradiated films were obtained using the transmittance and reflectance measurements, in the wavelength range starting from 250 up to 2500 nm. The analysis of the absorption coefficient data revealed an allowed direct transition with optical band gap of 2.2 eV for the as-deposited films, which decreased to 2.06 eV after exposing film to gamma irradiation. It was observed that the Urbach energy values change inversely with the values of the optical band gap. The dispersion of the refractive index was interpreted using the single oscillator model. The nonlinear absorption coefficient spectra for the as-deposited and ?-irradiated p-quaterphenyl thin films were obtained using the linear refractive index.
Highlights
Conjugated organic materials, which have semiconductor properties, have ended up to be promising competitors for different applications in optoelectronics and molecular electronics [1,2,3,4,5,6,7]
We have studied the influence of gamma irradiation on the structure and the surface morphology as well as the optical properties of p-quaterphenyl thin films prepared by thermal deposition technique
Thin films with thickness of 1148 nm were prepared onto clean glass and quartz substrates for the investigation of structural and optical properties respectively. p-quaterphenyl thin films were irradiated at room temperature, by 50 kGy dose of Cobalt-60 gamma radiation at a dose rate of 6.316 kGy/h using an irradiation cell, which is available at the National Center for Radiation Research and Technology (NCRRT), Atomic Energy Authority (AEA), Cairo, Egypt
Summary
Conjugated organic materials, which have semiconductor properties, have ended up to be promising competitors for different applications in optoelectronics and molecular electronics [1,2,3,4,5,6,7]. Oligomers are one of the organic materials which have been effectively used as active materials as a part of organic transistors [8] or organic lightemitting diodes [9] These oligomers may be of utility due to their essentially high thermal stability and potential chemical compatibility with the processing required for integrated organic devices. We have studied the influence of gamma irradiation on the structure and the surface morphology as well as the optical properties of p-quaterphenyl thin films prepared by thermal deposition technique
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