Laser-induced transformation of H3 defects in natural diamonds
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-14 |
| Journal | UÄĂ«nye zapiski Kazanskogo universiteta. SeriĂą Estestvennye nauki/UÄĂ«nye zapiski Kazanskogo universiteta. SeriĂą Estestvennye nauki/UÄenye zapiski Kazanskogo gosudarstvennogo universiteta. SeriĂą Estestvennye nauki |
| Authors | ĐĄ. Đ. ĐŃĐ°Đ”ĐœĐșĐŸ |
| Institutions | Russian Academy of Sciences, Institute of Geology, Komi Science Centre |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Problem Addressed: High-power laser excitation used in Raman and Photoluminescence (PL) spectroscopy can induce localized heating, causing thermal annealing and transformation of nitrogen-related defects in natural diamonds, leading to inaccurate typomorphic analysis.
- Critical Threshold Identified: The study established that H3 defect annealing (intensity reduction) begins at a laser intensity > 0.1 MW/cm2 (corresponding to laser power > 1 mW).
- Transformation Threshold: H3 defect transformation into the â490 nmâ defect (proposed scheme: N-V-N -> N-V + N) is initiated at a higher intensity threshold of > 0.25 MW/cm2.
- Methodology: Controlled luminescence spectroscopy was performed on natural Ural diamonds using a 488 nm Argon laser, systematically varying intensity via optical filters and focusing objectives (10x and 50x).
- Practical Guidance: These thresholds provide necessary operational limits for spectroscopists to ensure that defect frequency analysisâa key typomorphic feature reflecting the diamondâs genetic historyâis not corrupted by laser-stimulated effects.
- Defect Stability: The H3 defect (504 nm ZPL) was confirmed to be highly susceptible to laser-induced thermal effects compared to the resulting â490 nmâ defect (493 nm ZPL).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Excitation Wavelength | 488 | nm | Argon laser source |
| Maximum Laser Power (Pmax) | 100 | mW | Used for intensity calculations |
| Measurement Temperature | 295 | K | Room temperature (RT) |
| H3 Zero-Phonon Line (ZPL) Position (RT) | 504.2-504.6 | nm | Observed during experiment |
| â490 nmâ Defect ZPL Position (RT) | 493.1-493.2 | nm | Observed after transformation |
| H3 Annealing Threshold (Intensity) | > 0.1 | MW/cm2 | Minimum intensity for H3 reduction |
| H3 Transformation Threshold (Intensity) | > 0.25 | MW/cm2 | Minimum intensity for H3 -> â490 nmâ conversion |
| H3 Annealing Threshold (Power) | > 1 | mW | Calculated minimum power |
| Laser Spot Diameter (10x objective) | 10 | ”m | Used for low-intensity tests |
| Laser Spot Diameter (50x objective) | 2 | ”m | Used for high-intensity tests |
| Diamond Raman Shift (T2g mode) | 1332 | cm-1 | Used for normalization and temperature monitoring |
| Maximum Raman Shift Deviation | 1.2 | cm-1 | Observed shift, within measurement error (no bulk heating detected) |
Key Methodologies
Section titled âKey MethodologiesâThe study employed controlled confocal Raman microspectroscopy (LabRam HR800) to monitor luminescence spectra changes under varying laser power densities:
- Sample Preparation: Natural diamond crystals from Ural placers were selected, specifically focusing on surface areas exhibiting green radiation stains (indicative of radiation damage).
- Excitation Setup: A 488 nm Argon laser was used. Laser power was precisely controlled using a series of optical density filters (D1-D4) to achieve attenuation factors up to 10,000x.
- Focusing and Intensity Calculation:
- Low-intensity tests used a 10x objective, resulting in a 10 ”m spot diameter.
- High-intensity tests used a 50x objective, resulting in a 2 ”m spot diameter.
- Laser intensity (q) was calculated using the formula q = P/S (Power/Area).
- Spectra Acquisition: Luminescence spectra (490-950 nm range) were recorded at room temperature (295 K).
- Monitoring Transformation: Experiments involved sequential spectrum registration at increasing laser intensities and extended exposure times (up to 41 minutes total exposure at the highest intensity).
- Data Analysis: Spectra were normalized to the diamond Raman peak (1332 cm-1). Defect transformation was quantified by tracking the ratio of integral intensities between the H3 band (504 nm) and the newly formed â490 nmâ band (493 nm).
- Thermal Monitoring: The position of the 1332 cm-1 Raman line was monitored. Minimal shift (< 1.2 cm-1) indicated the absence of critical bulk heating, confirming that observed defect changes were due to localized heating within the defect-rich surface layer.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings are crucial for applications requiring precise control over diamond defect states and stability under optical excitation:
- Quantum Sensing and Computing: Nitrogen-Vacancy (NV) centers (derived from nitrogen defects) are the basis for diamond-based quantum technologies. Controlling the thermal stability of precursor defects (like H3) is vital for reliable, scalable defect engineering and platform stability in quantum devices.
- Advanced Gemological Diagnostics: The established intensity thresholds ensure that non-destructive spectroscopic analysis (PL/Raman) used for determining the geological origin (typomorphism) of high-value diamonds is accurate and does not artificially alter the defect signature.
- High-Power Laser Optics: Diamond is used as a window or heat spreader in high-power laser systems. Understanding the thermal degradation and transformation thresholds of intrinsic defects helps predict material performance and lifetime under intense optical loads.
- Solid-State Laser Cooling: H3 defects are actively studied for their efficient anti-Stokes photoluminescence, a mechanism used for solid-state laser cooling. This research defines the maximum safe operating intensity to prevent H3 defect degradation during cooling experiments.
- Defect Engineering and Annealing Processes: The study provides quantitative data on the laser-stimulated annealing and transformation kinetics of H3 defects, informing industrial high-temperature/high-pressure (HTHP) treatment protocols used to modify diamond color and properties.
View Original Abstract
Raman spectroscopy is a modern spectroscopic technique well-suited for diamond research. However, heating by high-power lasers can induce thermal damage to solid materials. To examine the effects of laser radiation on nitrogen defects in diamond crystals, luminescence spectra recorded during controlled laser heating at the surface of natural diamonds with green stains were analyzed. By focusing on H3 defects, the laser intensity threshold at which defect annealing or transformation occurs was identified. The findings from this study offer practical guidance on determining the frequencies of nitrogen defects in natural diamonds using luminescence spectroscopy. Such frequencies are a key typomorphic feature of diamonds and reflect important aspects of their genetic history.