Luminescence lineshapes of nitrogen vacancy center in lonsdaleite and dual structure of diamond/lonsdaleite - a DFT study
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-05-02 |
| Journal | Scientific Reports |
| Authors | Khaled A Abdelghafar, Daniel ChoĂŻ, Khalid Askar |
| Institutions | Khalifa University of Science and Technology |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: NV Centers in Diamond/Lonsdaleite Structures
Section titled âTechnical Documentation & Analysis: NV Centers in Diamond/Lonsdaleite StructuresâSource Paper: Luminescence lineshapes of nitrogen vacancy center in lonsdaleite and dual structure of diamond/lonsdaleite: a DFT study (Scientific Reports, 2025)
Executive Summary
Section titled âExecutive SummaryâThis DFT study provides crucial theoretical insights into the electronic and optical properties of Nitrogen Vacancy (NV) centers within the hexagonal carbon allotrope, Lonsdaleite, and its biphasic structure with cubic diamond. These findings are highly relevant for engineers developing next-generation quantum materials.
- Quantum Material Validation: The calculated Zero-Phonon Line (ZPL) for neutral NV&sup0; in pure Lonsdaleite (2.29 eV) closely matches reported experimental values (2.32 eV), validating the model for hexagonal diamond quantum defects.
- Symmetry and Strain Effects: Off-c-axis NV¹ defects exhibit reduced symmetry (shifting from C&sub3;v to C&sub1;h) and localized strain, leading to the splitting of excited states, a key factor for manipulating spin properties.
- Electron-Phonon Coupling: The study confirms strong electron-phonon interactions, particularly for off-c-axis defects, evidenced by a high Huang-Rhys factor (S = 3.77, HSE06) in pure Lonsdaleite.
- Phonon Side Band Dominance: The off-c-axis NV¹ configuration shows the lowest Debye-Waller factor (W&subZPL) at 2.3-2.5%, indicating that luminescence is dominated by phonon side bands rather than the ZPL, critical for broadband quantum sensing.
- Methodology: Advanced computational techniques, including the HSE06 hybrid functional, Phonopy, and PyPhotonics, were employed to accurately simulate geometry, vibrational dynamics, and luminescence lineshapes.
- Application Relevance: These results offer valuable guidance for engineering diamond-based quantum materials for qubit implementation, quantum computing, and nanoscale sensing applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the Density Functional Theory (DFT) calculations, primarily utilizing the HSE06 hybrid functional for high accuracy.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Calculated ZPL (NV&sup0;) | 2.29 | eV | Pure Lonsdaleite |
| Calculated ZPL (NV¹) | 2.04 | eV | Pure Lonsdaleite, Off-c-axis |
| Calculated ZPL (NV&sup0;) | 2.37 | eV | (211L_D) Dual Structure, Cubic Phase |
| Calculated ZPL (NV¹) | 2.06 | eV | (211L_D) Dual Structure, Hexagonal Phase, Off-c-axis |
| Debye-Waller Factor (W&subZPL) | 2.49 | % | (4L_D) Dual Structure, Off-c-axis NV¹ (Lowest ZPL weight) |
| Debye-Waller Factor (W&subZPL) | 17.37 | % | (4L_D) Dual Structure, NV&sup0; in Cubic Phase (Highest ZPL weight) |
| Huang-Rhys Factor (S) | 3.77 | N/A | Pure Lonsdaleite, Off-c-axis NV¹ (HSE06) |
| Primary Phonon Peak Energy | 60 - 67 | meV | NV¹ in Lonsdaleite/Diamond structures |
| Plane-Wave Cutoff Kinetic Energy | 90 | Ry | DFT Ground State Calculations |
| Hartree-Fock Cutoff Energy | 180 | Ry | HSE06 Hybrid Functional Calculations |
Key Methodologies
Section titled âKey MethodologiesâThe investigation relied on advanced first-principles calculations to model the complex NV center configurations and their optical response.
- Ground State Electronic Structure: Investigated using DFT within the Quantum Espresso framework, employing a scalar-relativistic Optimized Norm-Conserving Vanderbilt Pseudopotential (ONCVPSP).
- Supercell Design: Large supercells were utilized to minimize defect interaction: 576 lattice points for pure Lonsdaleite, and 320 (4L_D) or 647 (211L_D) atoms for the cubic diamond/lonsdaleite biphasic models.
- Functional Selection: Geometry optimization used the Perdew-Burke-Ernzerhof (PBE) functional, while electronic and ZPL calculations utilized the highly accurate Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional.
- Geometry Optimization: Achieved using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, with stringent convergence thresholds (1×10<sup>-6</sup> Ry total energy; 1×10<sup>-4</sup> Ry/bohr force).
- Phonon Calculations: Dynamic stability and vibrational modes were calculated using the open-source Phonopy code, deriving atomic force constants from DFT calculations.
- Luminescence Lineshape Modeling: Electron-phonon coupling spectral density $S(\hbar\omega)$ and luminescence lineshapes $L(\hbar\omega)$ were calculated using the PyPhotonics post-processing code, incorporating the Huang-Rhys factor and Fourier transformation of the generating function $G(t)$.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for highly controlled, high-purity diamond materials to realize quantum technologies based on specific NV center configurations and controlled crystal interfaces. 6CCVD is uniquely positioned to supply the necessary materials and customization services to replicate and extend this foundational work.
| Research Requirement / Challenge | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High-Purity Host Lattice (Cubic/Hexagonal) | Optical Grade Single Crystal Diamond (SCD) | Our SCD material offers ultra-low intrinsic defect density, providing the pristine environment required for precise NV center creation and minimizing unwanted background luminescence. |
| Modeling Dual Structures (Lonsdaleite/Diamond) | Custom Crystallographic Orientation & Thickness | 6CCVD provides SCD plates with precise orientation control and custom thicknesses (0.1 ”m to 500 ”m), enabling the experimental realization of the modeled (111)/(0001) interfaces and layered structures. |
| Controlled Defect Engineering (NV&sup0; / NV¹) | Custom Nitrogen Doping & Post-Growth Processing | We offer controlled nitrogen incorporation during MPCVD growth, essential for achieving optimal NV precursor concentration, alongside post-growth annealing and irradiation services to tune the NV charge state (NV&sup0; vs. NV¹). |
| Integration with Quantum Devices | In-House Custom Metalization Services | We provide internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for creating low-resistance ohmic contacts or integrated microwave/optical structures directly on the diamond surface, facilitating device integration. |
| Minimizing Surface Effects (Strain/Coherence) | Ultra-Low Roughness Polishing (Ra < 1 nm) | Our proprietary polishing techniques achieve surface roughness (Ra) below 1 nm on SCD, crucial for minimizing surface-induced strain and preserving the long coherence times required for qubit operation. |
| Scaling Up Quantum Sensing | Large-Area Polycrystalline Diamond (PCD) | For applications requiring large-scale arrays or imaging, we supply high-quality PCD wafers up to 125 mm in diameter, polished to Ra < 5 nm, offering a cost-effective path to commercialization. |
Engineering Support
Section titled âEngineering SupportâThe findings regarding the distinct ZPL and electron-phonon coupling characteristics of NV centers in Lonsdaleite structures are vital for optimizing quantum sensors and qubits. 6CCVDâs in-house PhD team specializes in defect engineering and material optimization for Quantum Sensing and Qubit Implementation projects. We provide expert consultation on material selection (SCD vs. PCD), doping levels, and post-processing recipes to achieve targeted NV center properties (e.g., high ZPL weight or dominant phonon side bands).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.