Optimization of the coherence properties of diamond samples with an intermediate concentration of NV centers
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2021-01-19 |
| Journal | Results in Physics |
| Authors | O. R. Rubinas, V.V. Soshenko, S. V. Bolshedvorskii, A. I. Zeleneev, A.S. Galkin |
| Institutions | P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Texas A&M University |
| Citations | 15 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research investigates the optimization of nitrogen-vacancy (NV) center coherence properties in diamond samples characterized by an intermediate concentration of substitutional nitrogen (1017 - 1018 cm-3).
- Core Challenge Addressed: Increasing NV concentration typically degrades coherence time (T2*) due to nitrogen-related impurities. This work demonstrates compensation for this degradation via optimized postprocessing.
- Key Achievement (T2*): The dephasing time (T2*) was significantly improved, reaching 0.7 µs at the optimal electron dose, closely approaching the theoretical 13C decoherence limit (approximately 0.9 µs) for natural abundance diamond.
- Optimal Processing Parameters: An optimal electron irradiation dose of approximately 15 · 1017 cm-2 was identified, maximizing the conversion efficiency of nitrogen donors into NV centers.
- Sensitivity Enhancement: Optimal postprocessing procedures resulted in an estimated sensitivity improvement of approximately 2 times compared to non-optimal processes for DC magnetometry applications.
- Conversion Mechanism: The improvement in T2* is achieved by converting substitutional nitrogen donors (C-defects, S=1/2) into NV centers, primarily the neutrally charged NV0 state.
- Trade-off: While T2* is improved, the conversion process leaves only 15% of the total NV centers in the useful negative charge state (NV-) at the optimal dose, which does not solve the problem of sample absorption.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Investigated Nitrogen Concentration Range | 1017 - 1018 | cm-3 | Substitutional N donors (0.6 - 5.6 ppm) |
| Optimal Electron Irradiation Dose | 15 · 1017 | cm-2 | Dose maximizing T2* improvement |
| Electron Irradiation Energy | 3 | MeV | Used for vacancy creation |
| Annealing Temperature | 800 | °C | Post-irradiation thermal treatment |
| Maximum Dephasing Time (T2*) Achieved | 0.7 | µs | At optimal dose (15·1017 cm-2) |
| 13C Decoherence Limit (T2*) | ~0.9 | µs | Theoretical limit for natural abundance diamond |
| Maximum Coherence Time (T2) Observed | 179.88 | µs | Observed at 4·1017 cm-2 dose |
| Total NV Center Conversion Saturation (γ) | 48 | % | Saturation level achieved via fitting model |
| Useful NV- Fraction (κ) at Optimal Dose | 15 | % | Fraction of total NV centers in the negative charge state (NV-) |
| Sensitivity Improvement Factor | ~2 | Times | Compared to non-optimal postprocessing for DC magnetometry |
| NV- Absorption Peak | 637 | nm | Used for concentration measurement at -77 K |
| NV0 Absorption Peak | 575 | nm | Used for concentration measurement at -77 K |
Key Methodologies
Section titled “Key Methodologies”The study utilized a combination of diamond growth, postprocessing, and advanced spectroscopic techniques:
- Diamond Growth: Diamond plates were grown using the low strain High-Pressure High-Temperature (HPHT) technique.
- Postprocessing (Irradiation): Samples were irradiated with a 3 MeV electron beam, varying the dose from 2·1017 to 20·1017 cm-2 to control vacancy creation.
- Postprocessing (Annealing): All samples were annealed at 800 °C to mobilize vacancies, allowing them to combine with substitutional nitrogen donors to form NV centers.
- Substitutional Nitrogen Measurement (nc): Electron Paramagnetic Resonance (EPR) spectroscopy was employed, calibrated using a reference sample measured via Infrared (IR) spectroscopy (specifically the 1130 cm-1 absorption peak).
- NV Center Concentration Measurement (nNV- and nNV0): Optical transmission spectroscopy was performed at cryogenic temperature (-77 K) using a Vertex 80v Fourier-transform spectrometer to quantify the concentrations of the negative (NV-) and neutral (NV0) charge states.
- Dephasing Time (T2*) Measurement: The T2* time was determined by fitting the decay of Ramsey fringes, implemented using a π/2-τ-π/2 microwave sequence.
- Coherence Time (T2) Measurement: The T2 time was measured using the Hahn echo sequence (π/2-τ-π-τ-π/2) under a high magnetic field (~80 Gauss) to mitigate 13C interactions and observe the coherence decay.
Commercial Applications
Section titled “Commercial Applications”The optimization of NV center coherence properties in high-density ensembles is critical for advancing several quantum and classical sensing technologies:
- Quantum Magnetometry: Enabling high-sensitivity magnetometers, particularly for DC field measurements, where the signal-to-noise ratio is directly tied to the NV concentration and T2*.
- Magnetic Field Imaging: Used in applications requiring high spatial resolution and sensitivity, such as mapping magnetic fields generated by biological samples or integrated circuits.
- Solid-State Quantum Information Processing: High-coherence NV ensembles are fundamental components for developing quantum memory and robust solid-state qubits.
- Gyroscopes and Accelerometers: NV centers are being explored for highly sensitive inertial sensing applications that rely on long spin coherence times.
- Material Characterization: Utilizing NV ensembles for highly localized sensing of temperature, strain, and electric fields within materials.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2013 - Nanoscale magnetometry with NV centers in diamond [Crossref]
- 2012 - Magnetocardiography with a modular spin-exchange relaxation-free atomic magnetometer array [Crossref]
- 2008 - High-sensitivity diamond magnetometer with nanoscale resolution [Crossref]
- 2018 - Spin properties of NV centers in high-pressure, high-temperature grown diamond [Crossref]
- 2009 - Diamonds with a high density of nitrogen-vacancy centers for magnetometry applications [Crossref]
- 2018 - Ultralong Dephasing Times in Solid-State Spin Ensembles via Quantum Control
- 2014 - Statistical investigations on nitrogen-vacancy center creation [Crossref]
- 2016 - Electron spin decoherence of nitrogen-vacancy center coupled to multiple spin baths [Crossref]
- 2011 - Magnetic field imaging with nitrogen-vacancy ensembles [Crossref]