Electron Paramagnetic Resonance Sensing of «Hidden» Atomistic and Cooperative Defects in Femtosecond Laser-Inscribed Photoluminescent Encoding Patterns in Diamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2023-08-28 |
| Journal | Photonics |
| Authors | S. V. Vyatkin, П. А. Данилов, Nikita Smirnov, Daniil A. Pomazkin, Evgeny V. Kuzmin |
| Institutions | Lomonosov Moscow State University, P.N. Lebedev Physical Institute of the Russian Academy of Sciences |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research utilized a multi-spectroscopic approach (FT-IR, EPR, PL) to analyze the complex atomistic and cooperative defect dynamics induced by femtosecond (fs) laser inscription in natural IaA-type diamond.
- Coupled Defect Dynamics: The study confirms that fs laser exposure drives an interrelated process involving the formation and migration of interstitial carbon atoms (Ci) and vacancies (V).
- Optically Active Defect Formation: Successfully increased the concentration of key photoluminescent (PL) centers associated with vacancies (H3, NV0, and NV-), validating the use of fs lasers for quantum emitter fabrication.
- “Hidden” Defect Sensing: Electron Paramagnetic Resonance (EPR) was critical for sensing optically blind defects, revealing a near twofold increase in the N2 center concentration (associated with broken C-C bonds/dislocations).
- Cooperative Effects Confirmed: FT-IR showed a significant increase in B2 centers (interstitial carbon platelets). This increase confirms the mobility of Ci in the diamond lattice at room temperature and establishes platelets as reservoirs for emerging interstitials.
- Structural Center Depletion: Defects not associated with vacancies or interstitials—specifically A centers (N-N pairs, decreased by >13%) and paramagnetic P1 and W7 centers—were depleted due to laser-induced structural transformation.
- Engineering Insight: The results provide quantitative data on how laser parameters affect both point defects (NV centers) and complex lattice damage (B2, N2 centers), crucial for optimizing quantum encoding recipes.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Type | Natural IaA | N/A | Octahedral crystal, 62 mg. |
| Initial A Center Conc. | ≈300 | ppm | Two neighboring substitutional N atoms (FT-IR). |
| Modified A Center Conc. | ≈260 | ppm | After laser exposure (13% decrease). |
| Initial P1 Center Conc. | 0.22 | ppm | Single substitutional N (EPR). |
| Modified P1 Center Conc. | 0.16 | ppm | After laser exposure. |
| Initial N2 Center Conc. | 0.09 | ppm | Broken C-C bonds/dislocations (EPR). |
| Modified N2 Center Conc. | 0.17 | ppm | After laser exposure (nearly twofold increase). |
| Laser Wavelength | 525 | nm | Femtosecond TEMA laser source. |
| Pulse Duration | 0.2 | ps | Ultrashort pulse regime. |
| Repetition Rate | 80 | MHz | High repetition rate. |
| Pulse Energy | 30 | nJ | Energy per pulse. |
| Focusing Objective | 0.25 | NA | Micro-objective. |
| Inscription Depth | ≈380 | µm | Above the bottom surface. |
| Inscription Speed | 300 | µm/s | Writing speed for line patterns. |
| Pulses per Point (N) | ≈1.3 x 106 | N/A | Exposure dose per point. |
| B2 Center Peak (Modified) | 1.7 | cm-1 | Peak absorption index after laser exposure (FT-IR). |
| B2 Center Area Increase | 17 to 30 | cm-2 | Increase in peak area, indicating platelet growth. |
Key Methodologies
Section titled “Key Methodologies”The study employed a high-repetition-rate femtosecond laser system combined with three complementary spectroscopic methods to characterize defect changes in a natural IaA diamond.
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Sample Material:
- Used a natural, transparent, flat-faced, octahedral IaA-type diamond (62 mg).
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Femtosecond Laser Inscription:
- System: TEMA femtosecond laser (Avesta Project).
- Parameters: 525 nm wavelength, 0.2 ps pulse duration, 80 MHz repetition rate, 30 nJ pulse energy.
- Pattern: 17 separated layers (96 µm interlayer distance) were inscribed at a depth of ≈380 µm. Each layer was 2x2 mm, consisting of lines written at 300 µm/s (period 10 µm).
- Focusing: Achieved using a 0.25-NA micro-objective.
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Fourier-Transform Infrared (FT-IR) Spectroscopy:
- Equipment: Optics IFS-125HR spectrometer with Hyperion 2000 microscope.
- Analysis: Used to quantify bulk nitrogen aggregation forms:
- A centers (N-N pairs, 1282 cm-1).
- B1 centers (N4V, 1175 cm-1).
- B2 centers (interstitial carbon platelets, 1363.5 cm-1).
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Photoluminescence (PL) Microspectroscopy:
- Equipment: 3D-scanning confocal Raman/PL microspectroscopy (Confotec MR520).
- Excitation: 532 nm and 405 nm lasers.
- Analysis: Used for visualization and quantification of optically active color centers:
- H3 (N-V-N, ZPL 503 nm).
- NV0 (ZPL 575 nm).
- NV- (ZPL 637 nm).
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Electron Paramagnetic Resonance (EPR) Spectroscopy:
- Equipment: Varian E-115 spectrometer (X-band, ≈9.4 GHz).
- Settings: Modulation amplitude 0.1 mT, modulation frequency 100 kHz, microwave power 5 mW.
- Orientation: Crystal oriented along the 4-order axes (H0 parallel to L4n).
- Analysis: Used to quantify paramagnetic centers, including the “hidden” defects:
- P1 (single substitutional N).
- W7 (N-C-C-N chain).
- N2 (fragments with broken C-C bonds/dislocations).
Commercial Applications
Section titled “Commercial Applications”The precise, localized control over defect creation in bulk diamond demonstrated by this research is foundational for several high-value engineering and commercial sectors:
- Quantum Information Processing (QIP):
- Enabling the deterministic placement and high-yield formation of NV- centers, which are leading candidates for solid-state qubits and quantum memory.
- High-Sensitivity Sensing:
- Development of advanced NV-based magnetometers, electrometers, and thermometers, leveraging the controlled creation of NV centers deep within the diamond matrix for non-invasive measurements.
- Secure Data Storage and Encoding:
- Fabrication of robust, invisible (stealth) microscale encoding patterns for anti-counterfeiting, product authentication, and secure data storage in high-value materials like diamonds.
- Advanced Optical Components:
- Engineering diamond materials with tailored optical properties (e.g., specific photoluminescence characteristics) for use in high-power optics, scintillators, and specialized windows.
- Materials Science Research:
- The methodology provides a powerful tool for studying the kinetics and stability of complex defects (like N2 and B2 centers) under extreme conditions, informing future diamond synthesis and post-processing techniques.
View Original Abstract
The changes that appeared in the crystal structure of a natural diamond under the influence of a pulsed femtosecond laser (525 nm) were comprehensively investigated using Fourier-transform infrared (FT-IR), electron paramagnetic resonance (EPR), and photoluminescence (PL) spectroscopy methods. It is shown that changes in the crystal structure occur due to the laser-driven interrelated process of the appearance and migration of interstitial carbon atoms and vacancies. On the one hand, there are atomistic transformations related to a decrease in the concentrations of structural centers that are not associated with vacancies or interstitial atoms—centers A (FT-IR spectroscopy) and P1 and W7 (EPR)—and an increase in the concentration of the H3, NV0, and NV− (PL) centers, which are associated with vacancies. On the other hand, there are indications of cooperative effects—an increase in the intensity of multi-atomic B2 (platelets, layers of interstitial carbon atoms (FT-IR)) and N2 (fragments of the structure with broken C-C bonds (EPR)) centers.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
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