Traceability of Diamonds Using UV-VIS-NIR Spectroscopy

At a Glance

Metadata	Details
Publication Date	2025-10-20
Journal	Minerals
Authors	D. GIURGIU, Ion Smaranda, Adelina Udrescu, M. Baibarac
Institutions	National Institute of Materials Physics, Alexandru Ioan Cuza University
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Traceability via Spectroscopy

Executive Summary

This research successfully demonstrates the use of combined UV-VIS-NIR and Raman spectroscopy as an objective method for assessing the geographical provenance of natural diamonds. The findings underscore the critical role of nitrogen impurity concentration and specific nitrogen-vacancy (NV) defect centers in material identification.

Core Achievement: Established a robust traceability method by correlating distinct optical signatures (UV-VIS-NIR absorption bands) and nitrogen concentrations (Raman FWHM) to geographical origin (Cullinan Mine vs. DRC).
Key Differentiator: Nitrogen concentration serves as the primary metric, showing a clear separation: Cullinan diamonds range from 41-185 ppm, while DRC diamonds range from 204-336 ppm.
Defect Analysis: Specific nitrogen-related centers (N1º, NVº, NV¯, N3Vº, N4V2, N1+, NVH) were identified via spectral deconvolution, providing unique fingerprints for each origin.
Methodology Validation: Raman FWHM measurements were successfully used to quantify nitrogen content, confirming the viability of this non-destructive technique for material characterization.
Provenance Assignment: Using these optical features, 83.33% of diamonds of unknown origin were successfully assigned to the Cullinan profile, validating the comparative power of the technique.
6CCVD Relevance: The precise control over nitrogen doping and defect engineering demonstrated in this paper is directly applicable to 6CCVD’s MPCVD capabilities for producing custom SCD and PCD materials for advanced optical and quantum applications.

Technical Specifications

The following hard data points were extracted from the spectroscopic analysis of the natural diamond samples:

Parameter	Value Range	Unit	Context
Nitrogen Concentration (Cullinan)	41 - 185	ppm	Calculated from Raman FWHM (A centers)
Nitrogen Concentration (DRC)	204 - 336	ppm	Calculated from Raman FWHM (C centers)
Raman Shift (Diamond Peak)	~1333	cm^-1	Characteristic vibrational mode of the cubic sublattice
Raman FWHM (Cullinan)	1.61 - 1.75	cm^-1	Full-Width Half-Maximum of the 1333 cm^-1 peak
Raman FWHM (DRC)	1.91 - 2.11	cm^-1	Full-Width Half-Maximum of the 1333 cm^-1 peak
UV-VIS-NIR Spectral Range	365 - 900	nm	Range used for absorption band measurement
NVº Center ZPL	575	nm	Zero-Phonon Line (ZPL) transition (2.156 eV)
NV¯ Center ZPL	637 - 638	nm	Zero-Phonon Line (ZPL) transition (1.945 - 1.947 eV)
N3Vº Center ZPL	415	nm	Zero-Phonon Line (ZPL) transition (2.987 eV)
H3 Center ZPL (N2V)	503	nm	Zero-Phonon Line (ZPL) transition (2.46 eV)

Key Methodologies

The study employed two primary, complementary spectroscopic techniques to characterize the diamond samples:

Sample Acquisition and Preparation:
- Total Samples: 65 natural diamonds (44 Cullinan, 9 DRC, 12 Unknown).
- Physical Characteristics: Weights varied from 0.042 ct to 4.43 ct; dimensions ranged from 1.4 mm to 8.8 mm.
- Polish Grade: Samples included both unpolished rough stones and polished cuts (e.g., Brilliant Cut, Pear Cut).
UV-VIS-NIR Spectroscopy (Defect Center Identification):
- Instrument: GemmoSphere™ spectrometer (Magi Labs.).
- Spectral Range: 365-900 nm.
- Resolution: 1.3 nm.
- Measurement Parameters: 50 scanning averages, 50 ms integration time.
- Analysis: Spectral deconvolution using a Voigt function to identify specific nitrogen-related defect centers (e.g., NV, N3V, N4V2, NVH).
FT Raman Spectroscopy (Nitrogen Quantification):
- Instrument: Bruker MultiRam FT Raman spectrophotometer.
- Excitation Source: YAG:Nd laser (1064 nm wavelength).
- Laser Power: 25 mW.
- Resolution: 2 cm^-1.
- Analysis: Measured the FWHM of the characteristic diamond peak (~1333 cm^-1). FWHM values were correlated to nitrogen concentration (N in ppm) using established empirical formulas for A centers (Cullinan) and C centers (DRC).

6CCVD Solutions & Capabilities

The research highlights the critical importance of controlling nitrogen impurities and resulting vacancy centers for diamond characterization and application. 6CCVD’s expertise in MPCVD growth allows for the precise engineering of these parameters, offering superior material control compared to the variability found in natural diamonds.

Applicable Materials

To replicate or extend the research on defect traceability, 6CCVD recommends the following materials, engineered for specific nitrogen and vacancy profiles:

Material Grade	Target Application/Research Focus	6CCVD Advantage
High-Purity SCD (Type IIa Equivalent)	Replication of low-N natural diamonds, fundamental studies of intrinsic defects, high-power optics.	Nitrogen concentration < 1 ppm, enabling the study of Type II characteristics and minimizing background absorption in the UV-VIS-NIR range.
Nitrogen-Doped SCD (NV Precursor)	Quantum sensing, NV center generation, replication of Type Ib/Ia characteristics (high N).	Precise control over substitutional nitrogen (N) concentration, essential for post-growth processing (irradiation/annealing) to maximize NVº and NV¯ yield and stability.
Optical Grade PCD	Large-area optical windows, high-throughput spectroscopic analysis, protective coatings.	Wafers up to 125mm diameter, offering excellent transparency across the UV-VIS-NIR spectrum for large-scale industrial traceability systems.
Boron-Doped Diamond (BDD)	Electrochemical sensing, semiconductor research (N1+ centers observed in DRC).	Custom BDD films and substrates for applications requiring p-type conductivity or specific charge states not achievable with nitrogen doping alone.

Customization Potential

The natural samples studied varied widely in size, shape, and polish. 6CCVD eliminates this variability by providing materials tailored precisely to experimental needs:

Custom Dimensions: We supply SCD plates up to 500µm thick and PCD wafers up to 125mm in diameter, far exceeding the size limitations of the natural samples used (max 8.8 mm). Substrates up to 10mm thick are available.
Precision Polishing: For high-resolution optical studies like those presented, surface quality is paramount. We offer ultra-smooth polishing:
- SCD: Roughness average (Ra) < 1 nm.
- Inch-size PCD: Ra < 5 nm.
Metalization Services: While not the focus of this paper, 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for researchers integrating diamond into electronic, sensor, or quantum device architectures.

Engineering Support

The successful traceability demonstrated relies on a deep understanding of defect physics and spectroscopic correlation. 6CCVD’s in-house PhD team provides authoritative support for similar projects:

Defect Engineering Consultation: Our experts assist clients in selecting the optimal MPCVD growth parameters (e.g., gas ratios, temperature, pressure) required to achieve specific defect concentrations (e.g., maximizing NV centers or controlling N-aggregate formation) for advanced [Optical Traceability and Quantum Sensing] projects.
Material Selection for Spectroscopy: We guide researchers in choosing the appropriate diamond type (SCD vs. PCD) and purity level to ensure reliable and reproducible UV-VIS-NIR and Raman results, minimizing spectral interference from unwanted impurities.
Global Logistics: 6CCVD ensures reliable global shipping, offering DDU (Delivered Duty Unpaid) as default and DDP (Delivered Duty Paid) options for seamless delivery of custom diamond materials worldwide.

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

View Original Abstract

Diamond traceability has been a major challenge for the gemological industry in recent decades. In this context, this paper presents new studies using UV-VIS-NIR spectroscopy to identify the traceability and geographical origin of diamonds. The aim of the work is to identify characteristic centers of fancy-color diamonds collected from Cullinan Mine, Democratic Republic of Congo (DRC), and the geographical regions with unknown origin. Depending on the origin of the diamonds, the UV-VIS-NIR spectra can be differentiated as follows: (i) the diamonds collected from Cullinan Mine show absorption bands assigned to N10, NV0, NV−, N3V0, N4V2, and N4V centers, which are accompanied by a vibronic structure localized between 415 and 394 nm (2.987-3.147 eV) and (ii) the diamonds from DRC show absorption bands attributed to N10, NV−, N3V0, N1+, and NVH centers. Using Raman spectroscopy, nitrogen concentration values of diamonds collected from the Cullinan mines and DRC between 41 and 185 ppm and 204-336 ppm, respectively, were reported. We prove that the simultaneous applicability of UV-VIS-NIR spectroscopy and Raman scattering as comparative tools for assessing diamond provenance can be a valuable strategy for an initial attribution of diamonds with unknown geographical origin, knowing the optical features of diamonds collected from Cullinan Mine and DRC.

Tech Support

Original Source

DOI: https://doi.org/10.3390/min15101091

References

2021 - Ultrathin diamond nanofilms—Development, challenges, and applications [Crossref]
2020 - Nitrogen in Diamond [Crossref]
2023 - Role of high nitrogen-vacancy con-centration on the photoluminescence and Raman spectra of diamond [Crossref]
2022 - From the lithosphere to the lower mantle: An aqueous-rich metal-bearing growth environment to form type IIb blue diamonds [Crossref]
2001 - Defects in coloured natural diamonds [Crossref]
2009 - SEM-based quantitative mineralogical analysis of peridotite, kimberlite, and concentrate [Crossref]
2013 - Recent advances in understanding the geology of diamonds [Crossref]
2022 - Mineral inclusions in lithospheric diamonds [Crossref]
2023 - Imperfections in natural diamond: The key to understanding diamond genesis and the mantle [Crossref]