Swift heavy ion induced optical modifications in LiF thin films

Swift heavy ion (SHI) induced optical modifications in LiF thin films were studied by UV–visible optical absorption and photoluminescence (PL) spectroscopies. LiF thin films of 200 nm thickness, deposited on glass substrate by resistive heating method, were irradiated with 80 MeV Ni ions in fluence range 1 × 1011–1 × 1014 ions/cm2. Optical absorption studies show a broad band peaked at 445 nm corresponding to F2/F3+ color centers. Optical absorbance of F2/F3+ color centers increases with increase in fluence. Since the bands of F2/F3+ could not be resolved by optical absorption, PL study has been performed by excitation source of 442 nm. PL spectra show two broad bands of F2 and F3+ color centers. The intensity of both the color centers increases up to 1 × 1012 ions/cm2 followed by an exponential decrease.