Nanoscale Vacancy-Mediated Aggregation, Dissociation, and Splitting of Nitrogen Centers in Natural Diamond Excited by Visible-Range Femtosecond Laser Pulses

At a Glance

Metadata	Details
Publication Date	2023-01-07
Journal	Nanomaterials
Authors	S. I. Kudryashov, G. Yu. Kriulina, П. А. Данилов, Evgeny V. Kuzmin, А. Н. Кириченко
Institutions	P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Lomonosov Moscow State University
Citations	5
Analysis	Full AI Review Included

Technical Documentation & Analysis: Nanoscale Nitrogen Center Transformation in Diamond

Reference Paper: Kudryashov et al., Nanoscale Vacancy-Mediated Aggregation, Dissociation, and Splitting of Nitrogen Centers in Natural Diamond Excited by Visible-Range Femtosecond Laser Pulses, Nanomaterials 2023, 13, 258.

Executive Summary

This research demonstrates precise, nanoscale control over nitrogen impurity centers in bulk diamond using femtosecond (fs) laser micro-inscription, a critical technique for quantum technology and nanophotonics.

Core Achievement: Controlled transformation of highly aggregated nitrogen centers (A, N3, H3, H4) into highly desirable, lowly aggregated Nitrogen-Vacancy (NV) centers (NVº, NV^-) within natural IaA+B diamond.
Mechanism: The transformation is vacancy-mediated, driven by interstitial-vacancy (I-V) Frenkel pair photogeneration induced by multi-photon absorption of 515 nm, 0.3 ps laser pulses.
Energy Dependence: Low pulse energies (< 0.6 µJ) promote vacancy-enriched aggregation (N3a, H3, H4). High, above-threshold energies (> 0.6 µJ) induce dissociation and concerted splitting, resulting in a high yield of NV centers.
Methodology: 3D scanning confocal Photoluminescence (PL) microspectroscopy (405 nm and 532 nm excitation) was used to map the resulting color center distribution at room temperature (RT) and liquid nitrogen temperature (LNT).
6CCVD Value Proposition: Replicating and scaling this work requires high-purity, low-nitrogen Single Crystal Diamond (SCD) substrates, which 6CCVD provides in custom dimensions up to 125 mm with ultra-low surface roughness (Ra < 1 nm) essential for high-NA focusing.

Technical Specifications

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

Parameter	Value	Unit	Context
Laser Wavelength	515	nm	Femtosecond pulse excitation
Pulse Duration	0.3	ps	Sub-picosecond regime
Repetition Rate	100	kHz	Pulse frequency
Pulse Energy Range	0.1 to 1.6	µJ	Variable energy for transformation control
Numerical Aperture (NA)	0.25	N/A	Micro-objective focusing
Focal Spot Radius (1/e)	2	µm	Estimated spot size
Inscription Depth	20 to 360	µm	Bulk modification region
NV^- Threshold Energy (E_th)	0.6	µJ	Energy required for transition to NV center formation
Characterization Excitation 1	405	nm	PL spectroscopy (N3, H3, H4 centers)
Characterization Excitation 2	532	nm	PL spectroscopy (NVº, NV^-, Vº centers)
Room Temperature (RT)	25	°C	PL measurement condition
Liquid Nitrogen Temp (LNT)	-120	°C	PL measurement condition
Initial Nitrogen Concentration (A centers)	~600	ppm	Natural IaA+B diamond precursor material

Key Methodologies

The experiment utilized a highly controlled ultrafast laser writing process followed by comprehensive 3D spectral analysis:

Material Preparation: Natural IaA+B diamond (high nitrogen content) was used. Initial characterization confirmed high concentrations of aggregated nitrogen (A, B1, B2 centers) via FT-IR and UV-near-IR transmission spectroscopy.
Laser Inscription Setup: A series of 515 nm, 0.3 ps pulses were focused into the bulk diamond using a 0.25 NA micro-objective, creating photoluminescent microtracks at depths of 20-360 µm.
Parameter Variation: Arrays of micromarks were inscribed by varying the incident pulse energy (0.1 to 1.6 µJ) and exposure time (10 s to 240 s, corresponding to 1M to 24M pulses).
3D Confocal PL Microspectroscopy: The resulting micromarks were analyzed using 3D scanning confocal PL microspectroscopy at two excitation wavelengths (405 nm and 532 nm) to identify specific color centers.
Temperature Analysis: Measurements were performed at both Room Temperature (RT, 25 °C) and Liquid Nitrogen Cooling Temperature (LNT, -120 °C) to observe temperature-dependent stability and ionization states (e.g., NVº vs. NV^-).
Spectral Analysis: Detailed analysis of PL spectra confirmed:
- Low energy/exposure: Rise in N3a, H3, and H4 centers (aggregation).
- High energy/exposure: Reduction in aggregated centers and predominance of NVº and NV^- centers (dissociation/splitting).

6CCVD Solutions & Capabilities

This research highlights the critical role of vacancy engineering and precise material control in creating functional quantum defects. 6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials necessary to transition this fundamental research into scalable engineering applications.

Applicable Materials

The paper used natural, high-nitrogen diamond. For high-fidelity quantum applications (e.g., single NV center creation, quantum memory), researchers require materials with tightly controlled impurity levels and superior crystalline quality.

Research Requirement	6CCVD Material Solution	Technical Advantage
High-Purity Substrates	Optical Grade SCD (Single Crystal Diamond)	Ultra-low intrinsic nitrogen (< 1 ppb) allows for precise, controlled introduction of vacancies and nitrogen via implantation or laser writing, maximizing NV yield and coherence time.
High-Power Handling	High-Thermal Conductivity SCD/PCD	Essential for managing thermal stress and preventing unwanted structural changes during high-repetition-rate fs laser processing.
Doping for Electrodes	Heavy Boron-Doped Diamond (BDD)	Can be used as a conductive layer or substrate for integrated nanophotonic devices requiring electrical contacts near the NV centers.

Customization Potential

The success of fs laser writing relies heavily on substrate quality, geometry, and integration readiness. 6CCVD offers comprehensive customization services that directly support the scaling and integration of this technology:

Custom Dimensions & Thickness: While the paper used a small 4x4x4 mm³ sample, 6CCVD provides PCD wafers up to 125 mm in diameter and SCD plates up to 500 µm thick, enabling industrial-scale processing and device fabrication. Substrates up to 10 mm thick are available for deep bulk inscription.
Surface Preparation: The use of a high-NA objective (0.25 NA) demands exceptional surface quality. 6CCVD guarantees ultra-low roughness polishing (Ra < 1 nm for SCD; Ra < 5 nm for inch-size PCD), minimizing scattering losses and ensuring accurate focal depth control during multi-photon absorption.
Integrated Metalization: For subsequent device integration (e.g., creating waveguides or electrodes for NV center control), 6CCVD offers in-house custom metalization using materials including Au, Pt, Pd, Ti, W, and Cu. This capability streamlines the path from material modification to functional device.
Precision Shaping: 6CCVD utilizes advanced laser cutting and shaping techniques to provide custom geometries required for specific optical setups or device architectures.

Engineering Support

The complex interplay between vacancy concentration, pulse energy, and nitrogen aggregation demonstrated in this paper requires deep material science expertise. 6CCVD’s in-house PhD team can assist with material selection and process optimization for similar NV Center Creation and Quantum Sensing projects. We ensure that the starting material properties (e.g., nitrogen concentration, crystal orientation) are perfectly matched to the desired laser processing recipe.

Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We offer global shipping (DDU default, DDP available) to support your research worldwide.

View Original Abstract

Natural IaA+B diamonds were exposed in their bulk by multiple 0.3 ps, 515 nm laser pulses focused by a 0.25 NA micro-objective, producing in the prefocal region (depth of 20-50 μm) a bulk array of photoluminescent nanostructured microtracks at variable laser exposures and pulse energies. These micromarks were characterized at room (25°) and liquid nitrogen cooling (−120 °C) temperatures through stationary 3D scanning confocal photoluminescence (PL) microspectroscopy at 405 and 532 nm excitation wavelengths. The acquired PL spectra exhibit a linearly increasing pulse-energy-dependent yield in the range of 575 to 750 nm (NV0, NV− centers) at the expense of the simultaneous reductions in the blue-green (450-570 nm; N3a, H4, and H3 centers) and near-IR (741 nm; V0 center) PL yield. A detailed analysis indicates a low-energy rise in PL intensity for B2-related N3a, H4, and H3 centers, while at higher, above-threshold pulse energies it decreases for the H4, H3, and N3a centers, converting into NV centers, with the laser exposure effect demonstrating the same trend. The intrinsic and (especially) photo-generated vacancies were considered to drive their attachment as separate species to nitrogen centers at lower vacancy concentrations, while at high vacancy concentrations the concerted splitting of highly aggregated nitrogen centers by the surrounding vacancies could take place in favor of resulting NV centers.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano13020258

References

2014 - Ultrafast lasers—Reliable tools for advanced materials processing [Crossref]
2021 - Preparations and applications of single color centers in diamond
2022 - Signatures of ultrafast electronic and atomistic dynamics in bulk photoluminescence of CVD and natural diamonds excited by ultrashort laser pulses of variable pulsewidth [Crossref]
2021 - Broadband and fine-structured luminescence in diamond facilitated by femtosecond laser driven electron impact and injection of “vacancy-interstitial” pairs [Crossref]
2021 - Ultrafast nonthermal NV center formation in diamond [Crossref]
2021 - Femtosecond-laser-excited luminescence of the A-band in natural diamond and its thermal control [Crossref]
2022 - Transformations of the Spectrum of an Optical Phonon Excited in Raman Scattering in the Bulk of Diamond by Ultrashort Laser Pulses with a Variable Duration [Crossref]
2017 - Laser writing of coherent colour centres in diamond [Crossref]