Extended and Point Defects in Diamond Studied with the Aid of Various Forms of Microscopy

Abstract

It is shown that star disclinations can be a significant source of stress in chemical vapor deposited (CVD) diamond. This purely geometrical origin contrasts with other sources of stress that have been proposed previously. The effectiveness is demonstrated of the use of electron irradiation using a transmission electron microscope (TEM) to displace atoms from their equilibrium sites to investigate intrinsic defects and impurities in CVD diamond. After irradiation, the samples are studied by low temperature photoluminescence microscopy using UV or blue laser illumination. Results are given that are interpreted as arising from isolated <100> split self-interstitials and positively charged single vacancies. Negatively charged single vacancies can also be revealed by this technique. Nitrogen and boron impurities may also be studied similarly. In addition, a newly developed liquid gallium source scanned ion beam mass spectrometry (SIMS) instrument has been used to map out the B distribution in B doped CVD diamond specimens. The results are supported by micro-Raman spectroscopy.

Optical centers introduced in boron-doped synthetic diamond by near-threshold electron irradiation

“…First, we demonstrated 2 that in one CVD specimen, GR1 was only generated at a grain boundary while 636 nm luminescence was generated throughout the irradiated region. Second, 6 we deduced that a region from which 636 nm luminescence was not previously observed produced a very strong 636 nm signal with 488 nm excitation after low temperature exposure to a 325 nm laser beam. In the regions where the 636 nm luminescence was generated the GR1 signal apparently decreased.…”

“…However, in the doping range 10 17 -10 19 cm Ϫ3 interesting, but poorly understood, optical centers can be introduced by energetic electron irradiation ͑energies տ200 keV͒. 4 Evidence has been presented that one of these centers is connected with a positive vacancy in diamond 6 although other researchers have identified a different center with the positive vacancy 7 and neither center has a transition energy close to the calculated energy of emission. 8 The aim of this work is to build on the preliminary investigations, referred to earlier, 2,4 of the optical centers introduced into B-doped diamond by near-displacement threshold electron irradiation.…”

“…6 The earlier work was taken to imply the conversion of GR1 into 666 nm luminescence by UV exposure. Our present results have produced a more ambiguous situation.…”

“…Some previous experiments indicated 6 that, under UV excitation, the intensity of neutral vacancy luminescence ͑GR1͒ was reduced irreversibly while that of the 636 and 666 nm ZPLs was increased. Experiments were therefore performed to investigate the possibility that the center giving 636 and 666 nm emission might be the positive vacancy in diamond.…”