Origin of intense blue-green emission in Sr Ti O3 thin films with implanted nitrogen ions: An investigation by synchrotron-based experimental techniques

The present study utilizes synchrotron-based x-ray diffraction (XRD), photoluminescence (PL), and x-ray absorption near edge structure (XANES) spectroscopic techniques to comprehend the evolution of optical intense blue-green emission in 100 keV nitrogen (N) ion implanted Sr Ti O3 (STO) thin films deposited by RF magnetron sputtering technique. The XRD pattern shows a shift in reflections at lower N ion fluences and the amorphization of the films at higher fluences. A disordered phase induced by implantation in the STO films leads to an intense blue-green emission due to oxygen (O) vacancies and N (2p) bound states. A schematic diagram of energy levels has been proposed to explain the origin of PL emission. The XANES spectra at Ti K edge reflect a change in the valency of Ti ions and the local atomic structure of ordered and disordered phases of STO with an increase in N ion fluence. The splitting of peak assigned to e g orbitals, and discrepancy in ratio dz2/dx2−y2 observed in the Ti L - and O K -edge spectra, confirm a distortion in Ti O6 octahedral structure and modifications in O 2p -Ti 3d hybridization states. The synchrotron-based techniques reveal that N ion implanted STO can be a good photoluminescent material exhibiting a variety of emissions through bound states of O vacancies and implanted N ions.