The most effective scheme for electrically activating ion implanted do
pants in diamond involves implantation at low temperatures (T-i less t
han or similar to 300 K) followed by rapid thermal annealing. For such
implantations, all defects (both vacancies and interstitials) are bel
ieved to be ''frozen in'', a fact which facilitates subsequent anneali
ng. In the present work, the nature of the defects introduced into dia
mond by low temperature implantations is determined by combining chann
elling, electrical conductivity, swelling and Raman measurements on ty
pe IIa diamonds irradiated with 320 keV Xe ions at T-i = 150 K over th
e dose range 1 x 10(13)-2 X 10(16) Xe cm(-2). The critical dose for am
orphization was found to correspond to an energy deposited in the modi
fied layer of 5.5 eV per C target atom. The carriers were determined t
o be holes for these cold implantations. The measurements suggest that
isolated point defects in diamond behave as accepters, whereas more c
omplex agglomerated defects behave as donors.