Optical absorption, interference and microscopic studies, of samples implanted with light ions (H+, D+, He+) and annealed, revealed new features of the bombardment-induced graphitization of diamond. One was a so-called low-temperature graphitization which was directly related to vacancies.

Defect-Induced Graphitisation in Diamond Implanted with Light Ions. A.A.Gippius, R.A.Khmelnitsky, V.A.Dravin, A.V.Khomich: Physica B, 2001, 308-310, 573-6