Dark defect charge dynamics in bulk chemical-vapor-deposition-grown diamonds probed via nitrogen vacancy centers

At a Glance

Metadata	Details
Publication Date	2020-05-12
Journal	Physical Review Materials
Authors	A Lozovoi, D. Daw, H. Jayakumar, C. A. Meriles, A Lozovoi
Institutions	City College of New York, The Graduate Center, CUNY
Citations	13
Analysis	Full AI Review Included

Technical Documentation & Analysis: Dark Defect Charge Dynamics in MPCVD Diamond

Reference: Lozovoi, D. et al. “Dark defect charge dynamics in bulk chemical-vapor-deposition-grown diamonds probing nitrogen vacancy centers.” (2023)

Executive Summary

This documentation analyzes a critical study utilizing MPCVD diamond to investigate charge dynamics relevant to quantum sensing and solid-state physics. The findings highlight the necessity of ultra-pure, highly controlled diamond material, a core offering of 6CCVD.

Core Achievement: The research successfully characterized charge dynamics in low-nitrogen Type 1b CVD diamond using Double Electron-Electron Resonance (DEER) spectroscopy and photo-conversion.
Key Discovery: Identification of a previously uncharacterized, optically and magnetically dark point defect (‘X’) featuring a deep acceptor level approximately 1.6 eV above the valence band.
Material Requirement: The experiment required custom-grown, high-purity MPCVD diamond (3x3x0.1 mm³) with ultra-low NV center concentration (≤ 10 ppb) and controlled substitutional nitrogen (P1) concentration (measured at 0.25 ± 0.03 ppm).
Implication for Quantum Technology: The dark defect X is found to be at least as abundant as the substitutional nitrogen, significantly impacting NV charge state control—a crucial parameter for quantum memory and sensing applications.
6CCVD Value Proposition: 6CCVD specializes in providing Quantum Grade Single Crystal Diamond (SCD) with precise, customized doping (N, B) and ultra-low defect density necessary to replicate and advance this fundamental research.

Technical Specifications

The following hard data points were extracted from the research paper, detailing the material properties and experimental results achieved using the CVD diamond samples.

Parameter	Value	Unit	Context
Sample Dimensions	3 x 3 x 0.1	mm³	Type 1b CVD Diamond Crystals
Total Nitrogen Concentration (Manufacturer Spec)	≤ 1	ppm	Used for growth baseline
NV Center Concentration (Manufacturer Spec)	≤ 10	ppb	Ultra-low NV density
Substitutional Nitrogen (N°) Concentration (Measured)	0.25 ± 0.03	ppm	Derived from DEER measurements (P1 centers)
Average Nitrogen Separation	28	nm	Calculated from N° concentration
Dark Defect X Acceptor Level	≈ 1.6	eV	Above the Valence Band (VB)
NV T₁-time (Spin Relaxation)	≈ 6	ms	Measured spin relaxation time
N° Tunneling Time (T_tun)	2.4 ± 0.7	ms	Characteristic decay time after green initialization
Magnetic Field Strength	17	mT	Aligned parallel to NV symmetry axis
Green Laser Excitation Wavelength	532	nm	Used for NV ionization and charge initialization
IR Bleaching Wavelength Range	710 - 780	nm	Used to determine Defect X energy level

Key Methodologies

The experiment relied on precise material engineering and advanced spin and optical spectroscopy techniques to characterize the charge dynamics within the diamond lattice.

Material Synthesis: Growth of Type 1b diamond crystals via MPCVD, specifically optimized for low nitrogen incorporation (Total N ≤ 1 ppm) to minimize the spin bath environment.
Spin Spectroscopy (DEER): Double Electron-Electron Resonance (DEER) sequence was employed to measure the dipolar coupling between NV^- centers and paramagnetic substitutional nitrogen (N° or P1 centers).
Optical Charge Initialization: NV centers were initialized into the NV^- state using 532 nm green laser pulses (30 µs, 1 mW), followed by a variable wait time (t_w) before MW application to monitor charge state decay.
Photo-Conversion Experiments: Multi-color excitation (532 nm, 632 nm, and 710-800 nm IR) was used to induce and monitor NV charge state interconversion (NV^- ↔ NV°) and characterize the energy level of the dark defect X.
Defect Energy Determination: The X acceptor level was determined by plotting the integrated NV^- photoluminescence as a function of IR illumination wavelength, confirming a single-photon absorption process.

6CCVD Solutions & Capabilities

This research underscores the critical role of highly controlled, low-defect MPCVD diamond in advancing quantum technology. 6CCVD is uniquely positioned to supply the materials required to replicate, scale, and extend this work.

Applicable Materials

To replicate the high-purity, low-strain environment necessary for stable NV center operation and precise charge dynamics studies, the following 6CCVD materials are recommended:

Quantum Grade Single Crystal Diamond (SCD): Required for the highest structural purity and lowest intrinsic defect density (Type IIa baseline). This material ensures that only intentionally introduced defects (like NV centers) dominate the spin dynamics.
Custom Doped SCD (Type 1b Equivalent): 6CCVD offers precise, controlled nitrogen doping during MPCVD growth to achieve specific P1 center concentrations (e.g., 0.25 ppm) necessary for spin bath engineering and NV creation.
Boron-Doped Diamond (BDD): For future studies involving p-type conductivity or electrochemical applications, 6CCVD provides BDD films with customizable doping levels.

Customization Potential

The paper utilized small, thin samples (3x3x0.1 mm³). 6CCVD’s manufacturing capabilities allow for exact replication or significant scaling of these specifications:

Requirement	6CCVD Capability	Specification Range
Custom Dimensions	Plates and wafers cut to specific geometries.	Up to 125 mm diameter (PCD); Custom plates (SCD).
Thickness Control	Precise control over active layer thickness.	SCD (0.1 µm - 500 µm); Substrates (up to 10 mm).
Surface Finish	Ultra-smooth surfaces critical for optical experiments.	Ra < 1 nm (SCD); Ra < 5 nm (Inch-size PCD).
Device Integration	In-house metalization for device prototyping.	Custom deposition of Au, Pt, Pd, Ti, W, Cu contacts.

Engineering Support

The discovery of the dark defect X highlights the complexity of charge state control in CVD diamond, which directly impacts the performance of quantum sensors and memories.

6CCVD’s in-house PhD engineering team specializes in material science for quantum applications. We offer consultation services to assist researchers in:

Material Selection: Choosing the optimal SCD or PCD grade based on required nitrogen concentration, strain tolerance, and surface orientation.
Defect Engineering: Developing custom growth recipes to minimize unwanted defects (like Defect X) or maximize the yield of specific color centers (NV, SiV, GeV).
Post-Processing: Advising on optimal annealing, irradiation, and surface termination protocols to achieve stable charge states for similar Quantum Sensing and Charge Dynamics projects.

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

View Original Abstract

Although chemical vapor deposition (CVD) is one of the preferred routes to\nsynthetic diamond crystals, a full knowledge of the point defects produced\nduring growth is still incomplete. Here we exploit the charge and spin\nproperties of nitrogen-vacancy (NV) centers in type-1b CVD diamond to expose an\noptically and magnetically dark point defect, so far virtually unnoticed\ndespite an abundance comparable to (if not greater than) that of substitutional\nnitrogen. Indirectly-detected photo-luminescence spectroscopy indicates a donor\nstate 1.6 eV above the valence band, although the defect’s microscopic\nstructure and composition remain elusive. Our results may prove relevant to the\ngrowing set of applications that rely on CVD-grown single crystal diamond.\n