Delayed luminescence and thermoluminescence in laboratory-grown diamonds

The “blue-green” phosphorescence/thermoluminescence is most commonly observed in diamonds following excitation at or above the indirect band gap and has been explained by a substitutional nitrogen-boron donor-acceptor pair recombination model. “Orange” and “red” phosphorescence have also been frequently observed in laboratory-grown near-colorless high-pressure high-temperature diamonds following optical excitation and their luminescence mechanisms are shown to be different from that of the blue-green phosphorescence. The physics of the orange and red luminescence and phosphorescence bands including the optical-excitation dependency (UV-NIR), temperature dependency (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>20</a:mn><a:mspace width="0.16em"/><a:mi mathvariant="normal">K</a:mi><a:mtext>–</a:mtext><a:mn>573</a:mn><a:mspace width="0.16em"/><a:mi mathvariant="normal">K</a:mi></a:mrow></a:math>), and related charge transfer process are investigated by a combination of self-built time-resolved imaging/spectroscopic techniques. In this paper, an alternative model for long-lived phosphorescence based on charge trapping is proposed to explain the orange phosphorescence/thermoluminescence band. Additionally, the red phosphorescence band is attributed to point defect, which possibly has a three-level phosphorescence system. Published by the American Physical Society 2024