Optical and microstructural properties of neutron irradiated RF- sputtered amorphous alumina thin films

Stoichiometric amorphous aluminium oxide thin films were deposited on glass substrate by the reactive sputtering technique. The films were exposed to varying thermal neutron fluence ranging from 6 × 1012 neutron/cm2 - 4 × 1013 neutron/cm2. The radiation induced changes in the structural, surface structural, and optical properties were investigated using X-ray diffraction, atomic force microscopy, and the UV-vis spectrophotometric analysis respectively. The structural phase of the film was not altered after irradiation, however, surface roughness parameters increased with neutron fluence. Empirical expression relating neutron dose and films' roughness were also derived. Furthermore, the optical transmittance, absorption and other related optical constants were affected by the neutron radiation. Possible reasons for the variations in optical properties of the films as a function of neutron fluence were discussed.