Rapid HPHT annealing of synthetic IB-TYPE diamonds

Abstract

The paper provides the information on the effects of rapid (1 minute) high pressure high temperature (RHPHT) annealing of synthetic Ib-type diamond plates at temperatures (1900 °C, 2100 °C, 2300 °C, 2500 °C, 2700 °C) and pressure of 8 GPa. The studies were carried out using the visual analysis, absorption and Raman spectroscopy, photoluminescence and cathodoluminescence. During RHPHT annealing the diamond plates in a high-pressure container were rapidly heated/cooled at a very non-uniform temperature and pressure distribution. All this caused the inhomogeneous plastic deformation of diamond plates. The plastic deformation of diamonds during RHPHT annealing was a powerful "generator" of vacancies. The electron transfer from individual atoms of substituting nitrogen to nitrogen-vacancy centers switched these centers to a negatively charged state. Another accompanying RHPHT annealing process was the diffusion of nitrogen atoms with the formation of it's simple aggregates -H3 defects (at 2300°C). At higher RHPHT annealing temperatures more complex aggregates containing three nitrogen atoms -N3 defectswere generated. RHPHT annealing led to the formation of identical nitrogenvacancy defects, as did quasi stationary HPHT annealing, but the number of these defects was significantly greater after RHPHT annealing.

Effect of the codoping of N–H–O on the growth characteristics and defects of diamonds under high temperature and high pressure

“…The Raman half-width reflects the crystallinity of the crystal, and a high FWHM is indicative of the low crystallinity and crystallization quality of diamonds. [32] Raman shift (cm -1 ) Moreover, when X i = 1.2%, the synthesized diamond crystal has the intrinsic Raman peak at 1331.5 cm −1 and clear Raman signals at 1418 cm −1 and 1542 cm −1 , among which the natural vibration peak of the graphite with sp 2 hybrid structure is located at 1542 cm −1 . These results indicate that the peak is caused by the sp 2 hybrid C in the synthesized diamond crystal.…”