Electron Paramagnetic Resonance Sensing of «Hidden» Atomistic and Cooperative Defects in Femtosecond Laser-Inscribed Photoluminescent Encoding Patterns in Diamond

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	Bauman Moscow State Technical University, P.N. Lebedev Physical Institute of the Russian Academy of Sciences
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Femtosecond Laser Defect Engineering in Diamond

Executive Summary

This document analyzes the research on femtosecond laser inscription in diamond, focusing on the generation and transformation of atomistic and cooperative defects. The findings are highly relevant to engineers developing quantum emitters and spintronics devices.

Core Mechanism: Ultrashort pulse (525 nm, 0.2 ps) laser irradiation generates carbon interstitial (C_i) and vacancy (V) pairs (Frenkel defects) deep within the diamond lattice (≈380 µm depth).
Cooperative Effects: The migration of laser-generated C_i atoms leads to a significant increase in cooperative defects, specifically B2 platelets (layers of interstitial carbon), evidenced by a near twofold rise in the B2 absorption index (from 1.0 cm^-1 to 1.7 cm^-1).
Vacancy-Driven Transformations: Vacancy formation drives the increase in paramagnetic N2 centers (0.09 ppm to 0.17 ppm) and optically active centers critical for quantum applications (H3, NVº, NV¯).
Defect Reduction: Non-vacancy-associated centers (A, P1, W7) decrease in concentration, confirming the laser-induced structural rearrangement of nitrogen impurities.
Methodological Advancement: The study successfully utilized complementary techniques (FT-IR, EPR, PL) to characterize both optically active and “hidden” paramagnetic defects (N2, W7), providing a comprehensive view of laser-driven defect dynamics.
Application Relevance: The precise control over defect creation and migration demonstrated is foundational for developing high-density, predetermined encoding patterns necessary for quantum computing and high-resolution sensing.

Technical Specifications

The following hard data points were extracted from the experimental methodology and results:

Parameter	Value	Unit	Context
Diamond Type Used	IaA (Natural)	N/A	High initial N content (≈300 ppm A centers)
Laser Wavelength	525	nm	Femtosecond pulse source
Pulse Duration	0.2	ps	Ultrashort pulse regime
Repetition Rate	80	MHz	Pulse frequency
Pulse Energy	30	nJ	Energy per pulse
Inscription Depth	≈380	µm	Above the bottom surface
Interlayer Distance	96	µm	Separation between inscribed layers
Initial A Center Conc.	≈300	ppm	Measured via FT-IR (1282 cm^-1 peak)
Modified A Center Conc.	≈260	ppm	13% decrease after laser exposure
B2 Absorption Index (Initial)	1.0	cm^-1	Measured via FT-IR (1363.5 cm^-1 peak)
B2 Absorption Index (Modified)	1.7	cm^-1	Indicates C_i migration and platelet growth
N2 Center Conc. (Initial)	0.09	ppm	Measured via EPR (Hidden paramagnetic center)
N2 Center Conc. (Modified)	0.17	ppm	Almost twofold increase post-irradiation
P1 Center Conc. (Initial)	0.22	ppm	Single substitutional N
P1 Center Conc. (Modified)	0.16	ppm	Decrease after laser exposure

Key Methodologies

The experiment relied on precise laser inscription combined with multi-modal spectroscopic analysis to track defect evolution:

Material Characterization: A natural IaA diamond crystal (62 mg) was selected, characterized by high initial concentrations of nitrogen in aggregated forms (A centers).
Femtosecond Laser Inscription: A 525 nm, 0.2 ps, 30 nJ pulsed laser was focused deep into the bulk using a 0.25-NA micro-objective.
Pattern Generation: The laser created 17 separated layers (2 x 2 mm) consisting of line series with a 10 µm period, written at 300 µm/s.
Fourier-Transform Infrared (FT-IR) Spectroscopy: Used to quantify changes in nitrogen aggregation centers (A, B1) and measure the absorption index of B2 platelets (interstitial carbon layers) at 1363.5 cm^-1.
Electron Paramagnetic Resonance (EPR) Spectroscopy: Performed in X-band (≈9.4 GHz) to detect and quantify paramagnetic centers (P1, W7, N2), including the optically “hidden” N2 center, and analyze their anisotropic distribution.
Photoluminescence (PL) Microspectroscopy: Used 405 nm and 532 nm excitation to visualize the inscribed layers and confirm the formation and increased intensity of key vacancy-related color centers (H3, NVº, NV¯).

6CCVD Solutions & Capabilities

6CCVD specializes in providing high-quality, custom MPCVD diamond materials that offer superior control and scalability compared to the natural diamond used in this study. Our synthetic materials are engineered to optimize the laser-induced defect transformations required for advanced quantum and spintronics applications.

Applicable Materials for Replication and Extension

The research highlights the need for precise control over initial nitrogen content to manage the resulting NV, H3, N2, and B2 concentrations. 6CCVD offers materials specifically tailored for this level of defect engineering:

Research Requirement	6CCVD Material Solution	Technical Advantage
High-Coherence NV Centers	Optical Grade SCD (Low Nitrogen Type IIa)	Nitrogen content controlled to the ppb level, minimizing unwanted N-aggregates (A, B1) that quench NV luminescence and reduce coherence time.
High-Density NV/H3 Creation	SCD (Type Ib)	Controlled, high-purity substitutional nitrogen (N_s) doping (ppm range) provides the necessary precursors for efficient NV and H3 formation upon laser irradiation.
Conductive Sensing Platforms	Boron-Doped Diamond (BDD)	Can be used as a substrate or active layer for integrated electrochemical or spintronic sensing devices, leveraging the laser-induced defects.

Customization Potential for Advanced Research

The successful replication and scaling of this femtosecond laser encoding technique require materials with specific dimensions, surface quality, and integration features, all of which 6CCVD provides:

Customization Requirement	6CCVD Capability	Relevance to Research
Large-Area Scaling	PCD Plates up to 125 mm Diameter	Enables the transition from small, natural crystals (62 mg) to industrial-scale wafers for high-throughput device fabrication.
Deep Bulk Focusing	SCD Substrates up to 10 mm Thickness	Provides the necessary depth for multi-layer encoding (17 layers inscribed in the paper) and 3D quantum circuit architectures.
High-Precision Optics	Polishing: SCD (Ra < 1 nm), PCD (Ra < 5 nm)	Ultra-smooth surfaces are critical for minimizing scattering and achieving tight, high-NA focusing deep into the bulk, preventing undesirable local graphitization noted in the paper.
Device Integration	Custom Metalization Services	We offer in-house deposition of Au, Pt, Pd, Ti, W, and Cu, allowing researchers to immediately integrate laser-encoded diamond into EPR/PL setups or microwave guides.
Custom Dimensions	Laser Cutting and Shaping	Precise custom dimensions and shapes for integration into specific experimental chambers or optical systems.

Engineering Support

The paper details complex, interrelated defect dynamics (C_i migration, N2 anisotropy, B2 growth). 6CCVD’s in-house PhD team offers authoritative professional support to navigate these challenges:

Material Selection Guidance: We assist researchers in selecting the optimal starting material (e.g., specific nitrogen concentration and aggregation state) to maximize the desired laser-induced transformations (e.g., NV formation) while minimizing unwanted side effects (e.g., N2 or B2 growth).
Defect Recipe Optimization: Our experts can consult on how CVD growth parameters influence the precursor defects (A, P1, W7) necessary for efficient conversion into NV and H3 centers via femtosecond laser processing.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-purity diamond materials directly to your lab.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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

Original Source

DOI: https://doi.org/10.3390/photonics10090979

References

2002 - Radiation hard diamond laser beam profiler with subnanosecond temporal resolution [Crossref]
2003 - Radiation detection devices made from CVD diamond [Crossref]
2021 - Deep diamond single-photon sources prepared by femtosecond laser [Crossref]
1982 - The structure and mechanism of formation of platelets in natural type Ia diamond [Crossref]
1986 - Platelets, dislocation loops and voidites in diamond [Crossref]
1995 - Conversion of platelets into dislocation loops and voidite formation in type IaB diamonds
2001 - Identification of the tetra-interstitial in silicon [Crossref]
2003 - Extended defects in diamond: The interstitial platelet [Crossref]
2017 - The relationship between platelet size and the B′ infrared peak of natural diamonds revisited [Crossref]