Cobalt ion implantation assisted modifications in luminescence, surface states, structural and morphological properties of MgTiO3 thin films

In the present work, the effects of ion implantation on structural, surface, optical, and photoluminescence behavior of MgTiO3 thin films have been investigated. Cobalt ions were implanted into crystalline films by varying the fluence from 3 × 1014 to 1 × 1016 ions/cm2. An intensity reduction and shift of the peak position upon implantation are attributed to amorphization and generation of strain, respectively. The root-mean-square roughness is reduced from 8.2 (pristine) to 6.4 nm upon implantation at 3 × 1014 ions/cm2 fluence and increases to 7.9 nm with a further upsurge in fluence. A non-monotonous variation in transmittance with implantation fluence is observed. The bandgap of pristine sample is ~ 4.22 eV, and the implanted samples exhibit a bandgap in the range of 4.03–3.88 eV. The surface chemical states of pristine and implanted films were analyzed using X-ray photoelectron spectroscopy. An enhancement in defects upon implantation of Co ions results in the variation of luminescence properties. A broad photoluminescence (PL) emission band extending from near UV to visible region is observed for the pristine film. The PL emission intensity is quenched upon implantation. Average decay lifetime of pristine film is observed to be 17.9 ns, which is slightly increased to 19.1 ns at 3 × 1014 ions/cm2 implantation fluence. Afterward, with a subsequent rise in implantation fluence from 1 × 1015 to 1 × 1016 ions/cm2, the average decay lifetime varied within the range of 17.2–18.9 ns. Factors responsible for different luminescent centers, structure, and morphology evolution as a consequence of Co ion implantation are reported.