Coloration of sapphire by Co ion implantation

Abstract

Co ions were implanted into colorless and transparent synthetic sapphires with doses of 5 × 10 16−5 × 10 17ions/cm 2 at an energy of 20 keV. The optical absorption spectrum and the XPS (X-ray photoelectron spectroscopy) spectrum were measured for as-implanted and annealed samples up to 1200 ° C in sequence. Although an as-implanted sample showed only dark grey, on heating the sample its color tone was gradually changed. The color turned green when it was heated at 800 ° C for 3 h. Light blue color was obtained by heating the sample at 1000 ° C for 3 h. XPS spectra of Co 2p 3 2 implanted into sapphire was changed when it was heated at 800 or 1000 °C. Although the spectra for the as-implanted sample almost coincided with that of pure metal, the spectrum for the annealed samples showed two peaks, one near the metallic state and the other at a distance of about 3 eV in the binding energy, which indicates the existence of two types of electronic configurations of Co with different binding energies in the colored sapphire.