Ion Implantation of Gemstones in Thailand and Our Reflections

Ion implantation of gemstones for gemological modification is a new development of ion beam technology applications in materials science. At Chiang Mai University, ion implantation of gemstones has been emphatically carried out with using ion species such as nitrogen and oxygen at the ion energy in a range of 20 to 120 keV to the ion beam fluences in a range of 10
¹⁷
to 10
¹⁹
ions/cm
²
. After ion implantation treatments, the gemological properties and thus qualities of gemstones were found improved in various degrees, such as changes in colors and tones, enhancements in transmittance, glittering and brilliance, homogenization of color distribution, and removal of inclusions and flaws. The ion-beam-treated gemstones were judged by gemologist professionals to confirm promotions of the gem grades. Ion implantation has advantages over conventional HTs, such as fast treatment, low temperature, and localized modification. Our work has been cited and commented by GIA (Gemology Institute of America) in their recent review. Although there have been impressive achievements, there is a commonly recognized puzzle in ion implantation induced color changes of gemstone, that is the ion range puzzle. The ion range is short; however, the gemological modification induced seems of bulk. Mechanisms involved in the color modifications are not yet well revealed and understood and they only remain in speculation. Ion beam parameters seem influential to the effects. Further research issues are proposed accordingly.