Photophysics of single nitrogen-vacancy centers in diamond nanocrystals
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-01-14 |
| Journal | Physical Review B |
| Authors | Martin Berthel, Oriane Mollet, GĂ©raldine Dantelle, Thierry Gacoin, S. Huant |
| Institutions | Ăcole Polytechnique, UniversitĂ© Grenoble Alpes |
| Citations | 94 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Photophysics of NV Centers in Nanocrystals
Section titled âTechnical Documentation & Analysis: Photophysics of NV Centers in NanocrystalsâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the photophysical characterization of Nitrogen-Vacancy (NV) centers in nanodiamonds (NDs) to inform material requirements for quantum applications. The research utilized second-order time-intensity photon correlation ($g^{(2)}(\tau)$) and a three-level system model to determine the intrinsic photophysical parameters of both the neutral (NV0) and negatively charged (NV-) states.
- Core Finding (NV-): The negative NV center exhibits distinct photon bunching behavior at finite delay, confirming the increasing role of a third, non-radiative âshelvingâ level, which drastically reduces the quantum yield (Q) from near unity to approximately 0.5 at high excitation power (P$_{exc}$).
- Core Finding (NV0): The neutral NV center shows negligible influence from the shelving level, maintaining a highly stable, near-unity quantum efficiency (Q $\sim$ 1.0) across the entire excitation power range studied (up to 10 mW).
- Methodology: Photophysical rates ($k_{ij}$) were successfully extracted by fitting the $g^{(2)}(\tau)$ function to a three-level Jablonski model, providing quantitative insights into excited and ground state dynamics.
- Material Relevance: The stability of both NV charge states is critically dependent on the crystal quality and the local electronic environment, validating the need for ultra-high-purity, controlled Single Crystal Diamond (SCD) as the host material for advanced single-photon sources and quantum sensors.
- 6CCVD Value: 6CCVD provides the necessary high-purity MPCVD SCD substrates, specialized thickness control (for implantation), and metalization services required to replicate this research and advance into integrated solid-state quantum devices.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Studied Material Form | Nanocrystals (NDs) | N/A | Size 50 nm or below, derived from HPHT diamond |
| Excitation Wavelength ($\lambda_{exc}$) | 515 | nm | Continuous Wave (CW) laser |
| Operating Temperature | Room | °C | Standard confocal setup |
| NV- ZPL Wavelength | 637 | nm | Negatively charged center (1.95 eV) |
| NV0 ZPL Wavelength | 575 | nm | Neutral center (2.16 eV) |
| NV0 Radiative Lifetime ($\tau_{21}$) | 19.2 | ns | Extracted spontaneous emission rate ($k_{21}$) at low power |
| NV- Radiative Lifetime ($\tau_{21}$) | 21.7 | ns | Extracted spontaneous emission rate ($k_{21}$) at low power |
| NV0 Quantum Yield (Q) | $\sim$ 1.0 | N/A | Constant over the 0.2-10 mW power range |
| NV- Quantum Yield (Q) Range | $1.0$ down to $0.5$ | N/A | Decreases with increasing excitation power |
| Maximum Excitation Power Studied (P$_{exc}$) | 10 | mW | Highest power used for $k_{ij}$ parameter analysis |
| NV- Bunching Parameter ($\beta$) | Up to $\sim 7$ | N/A | Increases significantly with excitation power (P$_{exc}$), linked to shelving state |
| NV0 Bunching Parameter ($\beta$) | $\sim 1$ | N/A | Remains constant, negligible bunching behavior |
Key Methodologies
Section titled âKey MethodologiesâThe study relied on a highly controlled material synthesis combined with advanced quantum optical measurements and theoretical modeling:
- Nanodiamond Synthesis: Commercial HPHT nanodiamonds were selected, followed by electron irradiation, high-temperature vacuum annealing (800 °C) to produce NV centers, and subsequent air annealing (550 °C) to remove surface graphitic compounds.
- Optical Setup: Single NV centers were addressed using standard confocal microscopy at room temperature, employing a CW 515 nm laser for non-resonant excitation.
- Photon Correlation: The core data was generated using a Hanbury-Brown and Twiss (HBT) intensity correlator setup to measure the second-order correlation function, $g^{(2)}(\tau)$, which characterizes single-photon emission (antibunching at $\tau=0$) and metastable level involvement (bunching at finite delay).
- Modeling (Three-Level System): The photophysics were modeled using Einsteinâs rate equations applied to a three-level Jablonski diagram (Ground, Excited, Metastable/Shelving Level) to solve for population dynamics.
- Parameter Extraction: Four key transition rates ($k_{12}, k_{21}, k_{23}, k_{31}$) were determined, enabling the calculation of the spontaneous emission rate ($k_{21}$) and the quantum yield (Q) as a function of excitation power.
- Photochromism Study: Dedicated HBT configurations utilizing selective bandpass filters (e.g., NV- filter in Start branch, NV0 filter in Stop branch) were used for cross-correlation measurements to characterize the charge state conversion dynamics.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research confirms the fundamental necessity of high-quality diamond materials for achieving stable and controllable single-photon emission. 6CCVDâs specialized MPCVD diamond capabilities directly address the needs of NV center research, from initial material selection to advanced device integration.
| Research Requirement/Application | 6CCVD Material/Capability Solution | Technical Advantage for Researchers |
|---|---|---|
| Pristine Host Matrix for NV Centers | Electronic Grade Single Crystal Diamond (SCD) wafers (low N, high purity) in custom dimensions (up to 125 mm). | Provides a superior, low-defect lattice compared to synthesized nanodiamonds, enabling higher control over NV concentration and environment for bulk or thin-film studies. |
| Near-Surface Defect Creation/Implantation | Custom Thin SCD Plates (Thickness 0.1 ”m to 500 ”m). | Optimization of ion implantation depth and efficiency required for creating near-surface NV centers ideal for sensing applications (magnetometry, plasmonics) and leveraging the demonstrated NV0 stability. |
| Control of NV Charge State/Fermi Level | Custom Boron-Doped Diamond (BDD) layers (SCD or PCD). | Enables external electrical tuning of the local Fermi level (as referenced in Ref. 65), facilitating systematic research into stabilizing the highly quantum-efficient NV0 state or suppressing the shelving behavior of NV-. |
| Photonic/Plasmonic Integration | Ultra-Fine Polishing (Ra < 1 nm for SCD, < 5 nm for Inch-size PCD). | Minimizes optical loss and surface roughness critical for integrating NV emitters into waveguides, plasmonic structures, or microcavities, essential for practical single-photon devices (Ref. 28). |
| Advanced Device Metalization | Internal Metalization Services (Au, Pt, Pd, Ti, W, Cu). | Allows researchers to integrate electrodes or contact pads directly onto the diamond substrate for electrical control, heating/cooling elements, or robust mounting in complex HBT or cryogenic setups. |
| Large-Scale Quantum Engineering | Polycrystalline Diamond (PCD) Wafers up to 125 mm diameter. | Offers scalable material solutions for developing larger arrays of NV-based sensors or high-power thermal management substrates, leveraging high PCD thermal conductivity. |
6CCVDâs in-house PhD team offers authoritative professional support to select the optimal diamond material (SCD, PCD, BDD) and specification (thickness, doping, orientation) tailored for complex quantum optics and solid-state physics projects, ensuring experimental success and repeatability.
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View Original Abstract
A study of the photophysical properties of nitrogen-vacancy (NV) color centers in diamond nanocrystals of size of 50~nm or below is carried out by means of second-order time-intensity photon correlation and cross-correlation measurements as a function of the excitation power for both pure charge states, neutral and negatively charged, as well as for the photochromic state, where the center switches between both states at any power. A dedicated three-level model implying a shelving level is developed to extract the relevant photophysical parameters coupling all three levels. Our analysis confirms the very existence of the shelving level for the neutral NV center. It is found that it plays a negligible role on the photophysics of this center, whereas it is responsible for an increasing photon bunching behavior of the negative NV center with increasing power. From the photophysical parameters, we infer a quantum efficiency for both centers, showing that it remains close to unity for the neutral center over the entire power range, whereas it drops with increasing power from near unity to approximately 0.5 for the negative center. The photophysics of the photochromic center reveals a rich phenomenology that is to a large extent dominated by that of the negative state, in agreement with the excess charge release of the negative center being much slower than the photon emission process.