Characteristics of La_0.7Sr_0.3MnO₃ Films Modified by Aluminum Ions Implantation and Post-Implantation Annealing

Abstract

The magnetron sputtered La 0.7 Sr 0.3 MnO 3 films were implanted with different doses (5 ′ 10 15 ions × cm?2 and 5 ′ 10 16 ions × cm -2 ) of Al ions at different negative pulsed voltages (30 kV and 50 kV) by plasma based ion implantation and then annealed at 973 K for 1 h in air. The microstructure, surface morphologies, surface roughness, metal-insulator transition and room temperature emittance properties of the post-implantation annealed films were investigated and compared with those of the La 0.7 Sr 0.3 MnO 3 film annealed at 973 K for 1 h in air. The results indicate that the post- implantation annealed films show single perovskite phase and obvious (100) preferred orientation growth. The Mn-O bond length, surface roughness and metal-insulator transition temperature (TMI) of the films can be effectively adjusted by changing implantation voltage or implantation dose of Al ions. However, the change of implantation parameters just has a small effect on room temperature emittance of the films. Compared with the annealed film, the post-implantation annealed films have shorter Mn-O bond length and lower room temperature emittance. The TMI of the films implanted at low voltage is lower than that of the annealed film, which mainly results from the degradation of oxidization during annealing process and the part displacement of Mn 3+ -O 2+ - Mn 4+ double exchange channels by Al 3+ -O 2? -Mn 4+ . The post-implanted annealed film implanted at 50 kV/5 ′ 10 16 ions × cm -2 has a higher TMI than the annealed film, which is 247 K. The increase of TMI of the film implanted with high dose of Al ions at high voltage can be attributed to the improvement of microstructure.