Swift Heavy Ion Irradiation Effects on Structural and Optical Properties of Nanocrystalline CeO₂ Films

Nano-crystalline CeO₂ films are deposited, on quartz substrates, by electron beam evaporation technique. Films are irradiated using 175 MeV Au¹³⁺ ions beams with three different fluences of 5 × 10¹¹ ions/cm², 1 × 10¹² ions/cm² and 5 × 10¹² ions/cm². The structural properties of as-deposited and irradiated films are investigated by glancing angle X-ray diffraction (GXRD) measurements. Raman modes are studied by Raman spectroscopy. Irradiation induced modification in the optical band gap of CeO₂ films is investigated by the UV-visible absorption spectroscopy. The surface morphology is studied by atomic force microscopy in tapping mode. Lower fluence irradiation leads formation of smaller sized nanocrystallites on the film surface. The irradiation dose of 5 × 10¹² ions/cm² diminishes the crystalline quality and erased the surface microstructures. The decrease in the band gap energy is the consequences of irradiation induced formation of various defect states in the film material.