arXiv subjects

Ben G. Breeze

Publications and source records attributed to Ben G. Breeze.

3 recordsLinked to original sources

arXiv2024

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 lab-grown near-colourless 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 (20 - 573 K), 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 are attributed to point defect which possibly has a three-level phosphorescence system.

cond-mat.mtrl-sci↗

arXiv2023

Phosphorescence and donor-acceptor pair recombination in laboratory-grown diamonds

Intense "blue-green" phosphorescence is commonly observed in near colourless lab-grown high-pressure high-temperature (HPHT) diamonds following optical excitation at or above the indirect bandgap. We have employed a holistic combination of optically-excited time-resolved techniques (in addition to standard spectroscopic characterisation techniques) to study the physics of this long-lived phosphorescence and understand luminescence-related charge transfer processes. It is shown that the properties of the broad "blue-green" luminescence and phosphorescence band can be fully explained by emission from neutral substitutional nitrogen-boron donor-acceptor pairs ($\text{N}_\text{S}^0$...$\text{B}_\text{S}^0$) , once the configurational change between charge states is considered, and both tunneling between defects and thermal ionization of donors and acceptors is considered. Significant concentrations of metastable $\text{N}_\text{S}^-$, are identified after optical excitation at or above the indirect bandgap. $\text{N}_\text{S}^-$ is much shallower ($\sim$0.2 eV) than previously thought and plays a key role in resetting the $\text{N}_\text{S}^0$...$\text{B}_\text{S}^0$ donor-acceptor pairs.

cond-mat.mtrl-sci↗

arXiv2017

All-optical hyperpolarization of electron and nuclear spins in diamond

Low thermal polarization of nuclear spins is a primary sensitivity limitation for nuclear magnetic resonance. Here we demonstrate optically pumped (microwave-free) nuclear spin polarization of $^{13}\mathrm{C}$ and $^{15}\mathrm{N}$ in $^{15}\mathrm{N}$-doped diamond. $^{15}\mathrm{N}$ polarization enhancements up to $-2000$ above thermal equilibrium are observed in the paramagnetic system $\mathrm{N_s}^{0}$. Nuclear spin polarization is shown to diffuse to bulk $^{13}\mathrm{C}$ with NMR enhancements of $-200$ at room temperature and $-500$ at $\mathrm{240~K}$, enabling a route to microwave-free high-sensitivity NMR study of biological samples in ambient conditions.

cond-mat.mes-hall↗