Blue Delayed Luminescence Emission in Neutral Nitrogen Vacancy Containing Chemical Vapor Deposition Synthetic Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-03-13 |
| Journal | physica status solidi (a) |
| Authors | Ff ion L. L. James, Amber M. Wassell, Colin D. McGuinness, Peter M. P. Lanigan, David Fisher |
| Institutions | Cardiff University |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis analysis focuses on the discovery and characterization of a novel, long-lived delayed blue luminescence (DBL) emission in nitrogen-doped Chemical Vapor Deposition (CVD) synthetic diamond.
- Novel Discovery: The first recorded instance of long-lived DBL centered at â465 nm, accompanied by sharp spectral peaks at 419, 455, and 499 nm, was observed in N-doped CVD diamond.
- Temperature Dependence: DBL is highly temperature-sensitive, dominating the delayed emission spectrum below 190 K (specifically strong at 77 K).
- Decay Mechanism Switch: At room temperature (290 K), the delayed emission is dominated by the neutral Nitrogen-Vacancy (NV0) center (575 nm). As temperature decreases, the DBL pathway becomes thermally activated, suppressing the NV0 emission.
- Long Lifetime: The DBL exhibits a long average decay lifetime, calculated up to 0.26 s at 77 K, suggesting the involvement of deep trap states and alternative decay pathways.
- Excitation Method: The luminescence was excited using short-wave UV radiation (190-227 nm), which is above the diamond bandgap (5.5 eV).
- Scientific Contribution: This finding introduces a new, previously undocumented optical signature in synthetic diamonds, contributing vital data for defect physics and gemological identification methods.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sample Type | CVD, N-doped | N/A | Untreated synthetic diamond gemstone |
| Nitrogen Concentration | 0.13 | ppm | Measured via UV absorption techniques |
| Excitation Wavelength Range | 190-227 | nm | Filtered xenon flash lamp (above bandgap) |
| Excitation Pulse Duration | 2.9 | ”s | Full-width half maximum (FWHM) |
| Measurement Temperature Range | 77-350 | K | Controlled cryostat environment |
| Delayed PL Start Time | 90 | ”s | Time delay after initial excitation pulse |
| DBL Emission Center | â465 | nm | Broad feature observed below 190 K |
| DBL Sharp Peaks | 419, 455, 499 | nm | Superimposed on the broad blue feature |
| NV0 ZPL Emission | 575 | nm | Zero-Phonon Line (ZPL) |
| DBL Average Decay Lifetime (77 K) | 0.26 | s | Longest recorded lifetime for DBL |
| DBL Average Decay Lifetime (190 K) | 0.14 | s | Lifetime decreases linearly up to 190 K |
| NV0 ZPL Redshift (77 K to 350 K) | 575.0 to 576.3 | nm | Shift attributed to thermal lattice expansion |
| NV0 ZPL Width Change (77 K to 350 K) | 0.46 to 3.51 | nm | Significant line broadening with temperature |
Key Methodologies
Section titled âKey MethodologiesâThe study employed a combination of temperature-dependent spectroscopy and time-resolved measurements to characterize the luminescence properties of the CVD diamond sample.
- Excitation Setup: A Hamamatsu Photonics L7685 xenon flash lamp was used, spectrally filtered to provide short-wave UV output (190-227 nm) with a 2.9 ”s pulse duration.
- Temperature Control: The sample was mounted in a cryostat allowing measurements across a wide range (77 K to 350 K).
- Prompt Photoluminescence (PL): Spectra were recorded concurrently with the excitation pulse (0 ”s delay) using a Horiba iHR-320 spectrometer and an Andor iCCD camera, primarily characterizing the NV0 center.
- Delayed Photoluminescence (PL): Spectra were recorded 90 ”s after the initial excitation, integrated over a 30 ms gate, to capture long-lived emission components.
- Time-Gated Imaging: A Basler Ace acA1920-40uc camera was used to visually capture the color evolution of the emission at fixed delays (0 ”s, 90 ”s, 70 ms) and varying temperatures (77 K, 150 K, 296 K). This confirmed the transition from yellow/orange (NV0) to blue (DBL) emission at low temperatures and long delays.
- Time-Resolved Decay Measurements: Decay curves were measured at 455 nm (DBL peak) and 575 nm (NV0 ZPL) using a photomultiplier tube. The data required multi-exponential fitting (3 or 4 exponentials) to account for simultaneous decay processes, and average decay lifetimes (Ï) were calculated based on the pre-exponential weighting.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings regarding the unique delayed luminescence signature in synthetic CVD diamond have direct relevance to several high-value engineering and commercial sectors:
- Gemological Technology (De Beers Ignite):
- The DBL serves as a novel, temperature-dependent optical signature for positively identifying synthetic CVD diamonds, enhancing the reliability of screening instruments like the De Beers SYNTHdetect.
- Understanding the thermal switching between NV0 and DBL pathways improves the robustness of authentication protocols used in the jewelry market.
- Quantum Information Science (QIS):
- The proposed existence of a âblue centerâ and associated trap states (Figure 6) impacts charge carrier dynamics and defect stability. This knowledge is critical for engineering diamond substrates optimized for NV-center-based quantum sensing and computing applications.
- Advanced Optical Materials:
- The long decay lifetime (up to 0.26 s) associated with the DBL suggests potential applications in specialized optical components requiring phosphorescence or controlled slow emission characteristics.
- Solid-State Lighting and Displays:
- The blue emission characteristics (465 nm) could inform the development of novel diamond-based phosphors or light-emitting structures, although further efficiency studies would be required.
View Original Abstract
Herein, the authors investigate the temperatureâdependent properties of delayed luminescence in an asâgrown nitrogenâcontaining chemical vapor deposition synthetic diamond gemstone when excited above its bandgap. At room temperature, this gemstone exhibits delayed luminescence from nitrogenâvacancy centers at 575 nm. However, at 77 K, the first recorded instance of a longâlived delayed blue luminescence centered at â465 nm, accompanied by spectral peaks at 419, 455, and 499 nm is reported. By analyzing spectral and temporal data at different temperatures, it can be speculated on potential photophysical transitions. This discovery documents the initial observation of this delayed luminescence emission, contributing to the collective understanding of synthetic diamonds.