Implantation sites of In, Cd, and Hf ions in diamond - art. no. 195207

The implantation sites of In, Cd, and Hf ions in diamond have been investig ated with complementary electron emission channeling (EC) and perturbed gam ma-gamma angular correlations (PAC) spectrometry on radioactive In-111, Cd- 111m, and Hf-181 probes implanted into natural type-IIa diamonds. The fract ion of probes occupying specific sites were determined from comparisons of the measured axial channeling yields with channeling patterns calculated us ing the many-beam formalism of electron motion through the crystal. For the In-implanted sample the EC measurements, after room-temperature implantati on and annealing at 1473 K or after implantation at 1373 K, show a substitu tional or near-substitutional fraction of 32(4)%, a tetrahedral interstitia l fraction of 10(3)%, and the remainder in highly disturbed environments. T he gamma-gamma PAC measurements confirm the near-substitutional population, but show that about 10% of the In probes are at sites with nearest-neighbo r point defects and 20% at sites with more distant defects, but none in a d efect-free environment. The Cd-111m measurements confirm these results and show that the loss of anisotropy in the PAC signal is not due to "aftereffe cts" of the electron capture decay of In to Cd, but due to extended lattice damage produced by the implantation process. The In PAC measurements confi rmed the previously observed In-defect interaction in diamond, with a quadr upole coupling frequency of nu (Q) = 117 MHz, and in addition, showed evide nce of a new defect interaction with nu (Q) = 315 MHz at annealing temperat ures above 1473 K. A diamond sample implanted with overlapping profiles of In-111 and hydrogen and annealed up to 1673 K showed no evidence of the hig her-frequency component or of any signal attributable to the formation of I n-H pairs. This suggests that in diamond no significant fraction of the imp lanted In atoms act as electrically active acceptors. In the Hf-181-implant ed diamond, the present EC and PAC measurements yield consistent results of a near-substitutional fraction of only 10%-15%, in contrast to earlier obs ervations.