Optical properties and structure characterization of sapphire after Ni ion implantation and annealing

Abstract

Implantation of 64keV Ni ions to sapphire was conducted at room temperature to 1×1017ions∕cm2 with a current density of 5 or 10μA∕cm2. Metallic Ni nanoparticles were formed with the 5μA∕cm2 ion current and the NiAl2O4 compound was formed with the 10μA∕cm2 ion current. The crystals implanted with both current densities were annealed isochronally for 1h at temperatures up to 1000°C in steps of 100°C in an ambient atmosphere. Optical absorption spectroscopy, x-ray diffraction, transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy have been utilized to characterize the samples. The surface plasmon resonance (SPR) absorption band peaked at 400nm due to the Ni nanoparticles shifted toward the longer wavelength gradually with the annealing temperature increasing from 400to700°C. The SPR absorption band disappeared after the annealing temperature reached 800°C. NiO nanoparticles were formed at the expense of Ni nanoparticles with an increasing annealing temperature. The TEM analyses revealed that the nanoparticles grew to 6–20nm and migrated toward the surface after annealing at 900°C. The absorption band at 430nm from Ni2+ cations in NiAl2O4 did not shift with the increasing annealing temperature.