Dense electronic excitation induced modifications in nanocrystalline zirconium oxide thin films: Detailed analysis of optical and surface topographical

Abstract Ion irradiation is known to create structural disorder and crystallization improvement in the material. In the present study, focus is on the effect of high energy ion beam irradiation on the optical, surface morphological and structural properties of ZrO2 thin films of 200 nm grown on Si and glass substrate by RF sputtering technique. The prepared thin films were annealed at 600 °C and irradiated with swift heavy ions (SHI) of 120 MeV Ti9+ ion beam with varied fluences ranging from 5E11 to 2E13 ions/cm2. SRIM simulation reveals that the electronic energy losses (Se) dominate over the nuclear energy losses (Sn) and the projected range of the Ti ions was found to be 13.64 μm. Optical properties were studied by using UV-Vis and Photoluminescence (PL) spectroscopy. The transmittance of the ZrO2 samples lies in the range of (46–79%) and the Tauc's plot was used to calculate the optical band gap. PL spectroscopy demonstrates the emission spectrum using the excitation wavelength of 310 nm. The influence of SHI irradiation on the surface morphology of ZrO2 thin films was examined by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The sectional analysis of AFM images reveals that the grain size decreases with increasing the ion fluences and lies in the range of 51-29 nm. The structural analysis of pristine and irradiated samples was done by using X-ray diffraction (XRD) technique. The crystallite size increases for the lower fluence up to 1E12 ions/cm2 and decreases at higher fluence due to the development of fragmentation by the effect of SHI irradiation. XRD patterns were used to calculate strain, stress, dislocation density and texture coefficient of the ZrO2 samples. Rutherford Backscattering Spectrometry (RBS) ensures the presence of Zr and O elements with the atomic fraction of 1: 2 and thickness (200 nm) of the samples was confirmed by simulating the RBS spectrum. The modifications induced in the properties of the ZrO2 thin films were mainly due to the electronic energy losses through the inelastic collision in the target material.