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6CCVD Research

Magnetic Resonance Study of Bulky CVD Diamond Disc

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-04-18
JournalMaterials
AuthorsAlexander I. Shames, A. M. Panich, Lonia Friedlander, Haim Cohen, J. E. Butler
InstitutionsAriel University, Ben-Gurion University of the Negev
Citations1
AnalysisFull AI Review Included

Magnetic Resonance Study of Bulky CVD Diamond Disc: Engineering Analysis

Section titled “Magnetic Resonance Study of Bulky CVD Diamond Disc: Engineering Analysis”

Executive Summary

Section titled “Executive Summary”

This study investigates the structural quality and defect landscape of a thick, sizable polycrystalline Chemical Vapor Deposition (CVD) diamond disc, focusing on nitrogen-related impurities using advanced magnetic resonance techniques.

  • Material Quality: The CVD diamond disc (50 mm diameter, 560 ”m thickness) exhibits low total nitrogen content (less than 90 ppm), primarily consisting of non-paramagnetic A-centers (N2 pairs) and paramagnetic C-centers (P1).
  • Structural Anisotropy: X-ray Diffraction (XRD) confirms a polycrystalline structure with a strong preferred growth orientation along the (111) plane. Crystallite sizes are highly anisotropic, ranging from greater than 1220 nm (111 direction) down to 4-90 nm (220 direction).
  • Defect Inhomogeneity: Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) data reveal significant macro- and micro-inhomogeneity in the distribution of nitrogen-related paramagnetic defects (P1 centers).
  • Relaxation Times: The 13C nuclear spin-lattice relaxation time (T1n) is inversely correlated with the local paramagnetic defect density (Ns), ranging from 1340 s (at Ns~5 ppm) to 2070 s (at Ns~3 ppm). This confirms that spin diffusion dominates relaxation.
  • Defect Types: Multiple types of P1 centers were identified based on relaxation behavior: well-isolated (slow relaxing), clusterized (faster relaxing), and exchange-coupled pairs.
  • Processing Stability: Post-processing treatments (e-beam irradiation, gamma irradiation, and high-temperature annealing) did not create new nitrogen-related centers, indicating high defect stability in this material structure.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Sample Diameter50mmFinal disc dimension
Sample Thickness560”mFinal disc dimension
Total Nitrogen Content<90ppmMeasured via FTIR spectroscopy
Primary Paramagnetic Centers (Ns)2.3 to 4.9ppmTotal content, sample dependent (EPR)
Substitutional N (P1) Content0.6 to 1.1ppmContent of P1 centers only (EPR)
13C NMR Frequency85.62MHzStatic mode, B0 = 8.0 T
1H NMR Frequency340.5MHzStatic mode
13C Spin-Lattice Relaxation (T1n)2070 ± 79sLow defect region (Ns~3 ppm)
13C Spin-Lattice Relaxation (T1n)1340 ± 126sHigh defect region (Ns~5 ppm)
Preferred Growth Orientation(111)N/AConfirmed by XRD
Crystallite Size (111 direction)>1220nmMicrometer-sized, strong preferred orientation
Crystallite Size (220 direction)4 to 90nmSignificantly smaller
P1 Electron Spin-Lattice Relaxation (TeSL)230”sSlow-relaxing P1 component
P1 Electron Spin-Lattice Relaxation (TeSL)0.21”sFast-relaxing P1 component (broad line)
Triplet Center (BS2) Zero Field Splitting (D)0.0908 ± 0.0001cm-1Associated with nitrogen clusters

Key Methodologies

Section titled “Key Methodologies”

The CVD diamond disc was grown using a home-built microwave plasma system (ASTeX components) on a molybdenum substrate. The process involved two distinct stages: nucleation and growth.

StageTime (h)Pressure (torr)Temperature (°C)Power (W)H2 Flow (sccm)CH4 Flow (sccm)O2 Flow (sccm)
Nucleation601158364974500180.5
Growth56.551158364974478202.0

Post-Processing and Characterization:

  1. Irradiation: Samples were treated with e-beam irradiation (1 kGy dose) and gamma irradiation (2 MGy dose).
  2. Annealing: Irradiated samples were annealed for 2 hours in a vacuum at 850 °C.
  3. EPR Spectroscopy: Continuous Wave (CW) X-band EPR was used in both slow passage (SP) and fast passage (FP) modes to identify and quantify paramagnetic defects (P1, BS1, P2, H1, BS2). Progressive power saturation experiments determined electron spin-lattice relaxation times (TeSL).
  4. NMR Spectroscopy: Static 13C and 1H NMR measured nuclear spin-lattice relaxation times (T1n), confirming the role of paramagnetic defects and nuclear spin diffusion in bulk relaxation.
  5. FTIR Spectroscopy: Used to quantify total nitrogen content (A-centers and C-centers) and detect C-H bonds (surface termination/grain boundaries).
  6. XRD Analysis: Bragg-Brentano geometry was used to determine crystallographic direction, preferred orientation, and estimate crystallite sizes using the Scherrer formula.

Commercial Applications

Section titled “Commercial Applications”

The properties of this bulky, low-nitrogen CVD diamond material make it suitable for demanding industrial and scientific applications requiring high purity, thermal stability, and specific defect characteristics.

  • Thermal Management:
    • Heat spreaders and laser sub mounts, leveraging diamond’s exceptional thermal conductivity.
    • X-ray targets requiring high heat dissipation.
  • Optical Systems:
    • Infrared (IR) windows and lenses.
    • Attenuated Total Reflection (ATR) units.
  • Radiation and Sensing:
    • Ionizing radiation detectors and dosimeters.
    • Fluorescence beam monitors.
  • Mechanical and Wear Resistance:
    • Cutting tools, scalpels, and knives.
    • Wear-resistant components (e.g., for textile machines).
  • Quantum Technology (Potential):
    • While NV- centers were not detected in the pristine or irradiated samples, the low background nitrogen (P1) content and long 13C T1n times (up to 2070 s) indicate a high-purity lattice suitable for subsequent targeted NV center creation or use in other solid-state quantum systems where low spin noise is critical.
View Original Abstract

Diamonds produced using chemical vapor deposition (CVD) have found many applications in various fields of science and technology. Many applications involve polycrystalline CVD diamond films of micron thicknesses. However, a variety of optical, thermal, mechanical, and radiation sensing applications require more bulky CVD diamond samples. We report the results of a magnetic resonance and structural study of a thick, sizable polycrystalline CVD diamond disc, both as-prepared and treated with e-beam irradiation/high-temperature annealing, as well as gamma irradiation. The combination of various magnetic resonance techniques reveals and enables the attribution of a plentiful collection of paramagnetic defects of doublet and triplet spin origin. Analysis of spectra, electron, and nuclear spin relaxation, as well as nuclear spin diffusion, supports the conclusion of significant macro- and micro-inhomogeneities in the distribution of nitrogen-related defects.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2022 - Synthesis of Diamonds and Their Identification [Crossref]
  2. 2005 - Magnetic resonance study of nanodiamonds [Crossref]
  3. 2006 - Processing Quantum Information in Diamond [Crossref]
  4. 1988 - EPR in diamond thin films sinthesized by microwave plasma chemical vapor deposition [Crossref]
  5. 1996 - Hydrogen-related defects in polycrystalline CVD diamond [Crossref]
  6. 1996 - Nitrogen-related dopant and defect states in CVD diamond [Crossref]
  7. 1994 - Power saturation and the effect of argon on the electron spin resonance of diamond deposited from a microwave plasma [Crossref]

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