Radiation damage in helium-implanted diamond

Diamond platelets were implanted with 8.8 MeV He²⁺ ions, the equivalent of alpha particles generated in the natural ²¹²Po ---> ²⁰⁸Pb decay (Th decay chain). Implantation densities were varied in the range 10¹² - 10¹⁷ ions per cm². Visible green colouration was produced at He²⁺ fluences _>10¹⁵ cm^-2. The radioinduced colour is mainly due to a broad absorption band at ca. 16000 cm^-1, which is assigned to the GR1 centre. Raman line scans showed that a narrow, stongly damaged area is formed ca. 29 µm below the sample surface. This corresponds very well with the distribution of Frenkel-type defects as predicted by Monte Carlo simulations using the SRIM program ¹. Raman data obtained from naturally radiocoloured diamonds are discussed in light of our new results.
¹ Ziegler JF, Biersack JP, Littmark U. The stopping and range of ions in solids. Pergamon Press, New York, 1985.