Structural, optical and magnetic properties of N ion implanted CeO2 thin films

Abstract

The present study reports the structural, morphological, optical and magnetic properties of N ion implanted CeO₂ thin films deposited by RF magnetron sputtering technique. These CeO₂ thin films were implanted with N ions having an energy of 80 keV with varying fluencies of 1 × 10¹⁵, 1 × 10¹⁶ and 6 × 10¹⁶ ions per cm², respectively. X-ray diffraction measurements show that as deposited films had predominantly (111) orientations. There is a significant change in the crystalline nature of these films after implantation compared to pristine film. RBS measurements confirm the presence of N ions in CeO₂ thin film with the highest fluence. The closely packed circular shaped nanoparticles were observed through AFM images both in pristine and N ion implanted CeO₂ films and these were agglomerated on the surface at a fluence of 6 × 10¹⁶ ions per cm². The crystalline structure and defect related information were evident through Raman spectroscopy. Raman results show that the crystalline structure is maintained even after implantation while the defect related peak is highest for the fluence value of 1 × 10¹⁵ ions per cm² and decreases thereafter. The magnetic measurements show enhanced ferromagnetic ordering in N ion implanted CeO₂ films compared to pristine film. The saturation magnetization is highest for the lowest fluence of N ions (1 × 10¹⁵ ions per cm²) which decreases with ion fluences. This diverse defect nature of oxygen vacancies (V_O) in the N ion implanted CeO₂ thin films mediates the ferromagnetic ordering.