Rapid HPHT annealing of synthetic IB-TYPE diamonds

Abstract

The paper provides the information on the effects of rapid (1 min) 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 defects — were generated. RHPHT annealing led to the formation of identical nitrogen – vacancy defects, as did quasi stationary HPHT annealing, but the number of these defects was significantly greater after RHPHT annealing.