Anomalous Formation of Irradiation-Induced Nitrogen-Vacancy Centers in 5 nm-Sized Detonation Nanodiamonds
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-03-14 |
| Journal | The Journal of Physical Chemistry C |
| Authors | Frederick T.-K. So, Alexander I. Shames, Daiki Terada, Takuya Genjo, Hiroki Morishita |
| Institutions | ETH Zurich, Kyoto University Institute for Chemical Research |
| Citations | 14 |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: Anomalous NV- Center Formation in Nanodiamonds
Section titled âTechnical Analysis and Documentation: Anomalous NV- Center Formation in NanodiamondsâExecutive Summary
Section titled âExecutive SummaryâThis research details the anomalous and highly efficient formation of negatively charged Nitrogen-Vacancy (NV-) centers in 5 nm Detonation Nanodiamonds (DNDs), providing critical insights for quantum sensor development.
- Anomalous Defect Creation: NV- centers in 5 nm DNDs are formed efficiently during low-temperature electron irradiation (max 100 °C) without the need for subsequent high-temperature annealing (typically 800 °C).
- âSelf-Annealingâ Mechanism: This unique behavior is attributed to a combination of âsize effectsâ (low heat capacity, low thermal conductivity) and âtype effectsâ (extremely high substitutional nitrogen concentration [Ns]).
- High Nitrogen Precursor: DNDs exhibit a substitutional nitrogen concentration ([Ns] estimated at 850-1100 ppm), which is approximately ten times higher than the HPHT nanodiamonds used for comparison (70-100 ppm).
- Superior Yield in Small Particles: Despite the small size (5 nm) leading to vacancy loss to the surface, the high [Ns] compensates, resulting in a higher NV- concentration than in larger 10 nm and 20 nm HPHT nanodiamonds.
- Non-Saturating Enrichment: Electron irradiation up to 1.5Ă1019 e-/cm2 showed a linear increase in NV- concentration in DNDs with no sign of saturation, confirming a deficiency of vacancies relative to the high concentration of nitrogen impurities.
- Quantification Method: The study reliably quantified NV- centers in nanodiamond powders using continuous-wave Electron Paramagnetic Resonance (EPR) spectroscopy via the half-field (HF) transition (geff = 4.23).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Nanodiamond Size (DND) | 5 | nm | Detonation Synthesis |
| Nanodiamond Size Range (HPHT) | 10 to 100 | nm | High-Pressure High-Temperature Synthesis |
| Electron Irradiation Energy | 1 and 2 | MeV | Used for vacancy creation |
| Electron Irradiation Fluence (Max) | 1.5Ă1019 | e-/cm2 | Highest fluence tested on DNDs, no saturation observed |
| Irradiation Temperature (Max) | 100 | °C | Temperature during electron irradiation |
| Conventional Annealing Temperature | 800 | °C | Standard annealing temperature (2 h in vacuum) |
| Substitutional Nitrogen [Ns] (DND) | 850 - 1100 | ppm | Estimated P1 center concentration |
| Substitutional Nitrogen [Ns] (HPHT) | 70 - 100 | ppm | Estimated P1 center concentration (20-100 nm NDs) |
| NV- Concentration (DND, Irradiated) | 1.3 | ppm | Highest concentration achieved before annealing (1.5Ă1019 e-/cm2) |
| NV- EPR Signal geff | 4.23 ± 0.01 | N/A | Half-field transition used for quantification |
| NV- Zero-Field Splitting (D) | â 2.87 | GHz | Characteristic of the NV- center |
| Annealing Temperature Scan Range | 400 to 800 | °C | Tested on irradiated DNDs (no significant change observed) |
Key Methodologies
Section titled âKey MethodologiesâThe study utilized a rigorous multi-step process combining material synthesis, defect creation, and advanced spectroscopic analysis:
- Material Sourcing: Comparison between commercial HPHT nanodiamonds (10-100 nm) and 5 nm Detonation Nanodiamonds (DNDs).
- Purification: All samples underwent boiling acid treatment (nitric acid/sulfuric acid mixture, 1:3 volume ratio) at 130 °C for 3 days to remove paramagnetic metal impurities (Fe3+) that interfere with EPR signals.
- Vacancy Creation: Electron irradiation was performed at two kinetic energies (1 MeV and 2 MeV) and various fluences (up to 1.5Ă1019 e-/cm2) on a water-cooled copper plate (T â 80 °C).
- Annealing Protocol: Conventional high-temperature annealing was performed at 800 °C for 2 h under high vacuum (p < 10-6 mbar). A temperature scan (400 °C to 800 °C) was also performed on irradiated DNDs.
- Defect Quantification (EPR): Continuous-wave Electron Paramagnetic Resonance (EPR) spectroscopy (X-band, v â 9.87 GHz) was used as the primary quantification tool, focusing on the half-field (HF) transition (geff = 4.23) specific to the S=1 NV- triplet defect.
- Structural Integrity Check: Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) confirmed that high-fluence electron irradiation did not cause significant lattice damage or graphitization (no increase in sp2 carbon Ï* transition at 285 eV).
- Theoretical Modeling: Monte Carlo simulations were employed to model vacancy migration probability as a function of particle diameter and substitutional nitrogen concentration [Ns], confirming the role of high [Ns] in compensating for vacancy loss in small particles.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research highlights the critical role of precise nitrogen concentration and controlled defect creation in maximizing NV- center yield, even in the presence of size constraints. 6CCVD, as an expert in MPCVD diamond synthesis, provides the foundational materials necessary to replicate and scale these quantum defect engineering breakthroughs in bulk and wafer formats.
Applicable Materials for Quantum Defect Engineering
Section titled âApplicable Materials for Quantum Defect Engineeringâ| Research Requirement | 6CCVD Material Solution | Key Capability Match |
|---|---|---|
| High Nitrogen Precursors | Type Ib Single Crystal Diamond (SCD) | High, controlled substitutional nitrogen doping (P1 centers) for high-density NV- creation via irradiation/annealing. |
| High Coherence/Low Noise | Ultra-High Purity Optical Grade SCD | Native nitrogen concentration < 1 ppb, ideal for creating isolated NV- centers via ion implantation (e.g., N+, Si+) where long coherence times (T2) are paramount. |
| Large-Area Quantum Arrays | Polycrystalline Diamond (PCD) Wafers | Custom plates/wafers up to 125 mm diameter, enabling scalable production of quantum sensors and integrated devices. |
| Boron Doping/Charge Control | Boron-Doped Diamond (BDD) | Essential for passive charge state control (NV0/NV- equilibrium) in quantum sensing devices, as referenced in related literature (Ref. 50). |
Customization Potential for Defect Creation
Section titled âCustomization Potential for Defect Creationâ6CCVDâs advanced fabrication capabilities directly support the precise defect engineering protocols demonstrated in this paper (irradiation and annealing):
- Custom Dimensions and Thickness: We supply SCD and PCD plates/wafers in custom dimensions and thicknesses (SCD/PCD: 0.1 ”m to 500 ”m; Substrates: up to 10 mm), optimized for high-energy electron or ion irradiation processes.
- Surface Preparation: Our SCD materials achieve ultra-smooth polishing (Ra < 1 nm), critical for surface-sensitive quantum sensors and minimizing surface defects that act as vacancy sinks. Inch-size PCD can achieve Ra < 5 nm.
- Integrated Metalization: For researchers integrating diamond quantum sensors into electronic or microwave circuits (e.g., for EPR or ODMR), 6CCVD offers in-house metalization services, including Au, Pt, Pd, Ti, W, and Cu deposition.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in MPCVD growth parameters and defect control. We offer consultation services to assist researchers in selecting the optimal diamond material (SCD vs. PCD, doping level, crystal orientation) required to replicate or extend high-yield NV- creation protocols for Quantum Sensing and Defect Physics projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Nanodiamonds containing negatively charged nitrogen-vacancy (NV$^-$) centers\nare versatile room-temperature quantum sensors in a growing field of research.\nYet, knowledge regarding the NV-formation mechanism in very small particles is\nstill limited. This study focuses on the formation of the smallest\nNV$^-$-containing diamonds, 5 nm detonation nanodiamonds (DNDs). As a reliable\nmethod to quantify NV$^-$ centers in nanodiamonds, half-field signals in\nelectron paramagnetic resonance (EPR) spectroscopy are recorded. By comparing\nthe NV$^-$ concentration with a series of nanodiamonds from high-pressure\nhigh-temperature (HPHT) synthesis (10 - 100 nm), it is shown that the formation\nprocess in 5 nm DNDs is unique in several aspects. NV$^-$ centers in DNDs are\nalready formed at the stage of electron irradiation, without the need for\nhigh-temperature annealing. The effect is explained in terms of\nâself-annealingâ, where size and type dependent effects enable vacancy\nmigration close to room temperature. Although our experiments show that NV$^-$\nconcentration generally increases with particle size, remarkably, the NV$^-$\nconcentration in 5 nm DNDs surpasses that of 20 nm-sized nanodiamonds. Using\nMonte Carlo simulations, we show that the ten times higher substitutional\nnitrogen concentration in DNDs compensates the vacancy loss induced by the\nlarge relative particle surface. Upon electron irradiation at a fluence of $1.5\n\times 10 ^{19}$ e$^-$/cm$^2$, DNDs show a 12.5-fold increment in the NV$^-$\nconcentration with no sign of saturation. These findings can be of interest for\nthe creation of defects in other very small semiconductor nanoparticles beyond\nNV-nanodiamonds as quantum sensors.\n
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2001 - Optical Properties of Diamond [Crossref]