NATURE OF DAMAGE IN DIAMOND IMPLANTED AT LOW-TEMPERATURES

The most effective scheme for electrically activating ion implanted dopants in diamond involves implantation at low temperatures (T-i less than or similar to 300 K) followed by rapid thermal annealing. For such implantations, all defects (both vacancies and interstitials) are believed to be ''frozen in'', a fact which facilitates subsequent annealing. In the present work, the nature of the defects introduced into diamond by low temperature implantations is determined by combining channelling, electrical conductivity, swelling and Raman measurements on type IIa diamonds irradiated with 320 keV Xe ions at T-i = 150 K over the dose range 1 x 10(13)-2 X 10(16) Xe cm(-2). The critical dose for amorphization was found to correspond to an energy deposited in the modified layer of 5.5 eV per C target atom. The carriers were determined to be holes for these cold implantations. The measurements suggest that isolated point defects in diamond behave as accepters, whereas more complex agglomerated defects behave as donors.