Особенности высокочастотной ЭПР/ЭСЭ/ОДМР спектроскопии NV-дефектов в алмазе
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | Физика твердого тела |
| Authors | Р.А. Бабунц, Д.Д. Крамущенко, А.С. Гурин, А.П. Бундакова, М.В. Музафарова |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research validates the use of Nitrogen-Vacancy (NV) centers in diamond for advanced quantum sensing applications under extreme conditions, specifically strong magnetic fields and cryogenic temperatures.
- High-Field ODMR Efficiency: Demonstrated that the optically induced spin polarization mechanism remains highly effective in strong magnetic fields (~3-5 T), achieving a photoluminescence (PL) intensity change of up to 10% at resonance.
- Spectroscopic Resolution: Successfully registered high-frequency (94 GHz, 130 GHz) EPR, ESE, and ODMR spectra, resolving hyperfine structure (HFS) components from both 14N and neighboring 13C nuclei.
- Enhanced Signal Intensity: Observed a significant increase in the ODMR signal intensity when the strong external magnetic field was aligned parallel to the NV center symmetry axis.
- Novel Methodology: Introduced a new ODMR registration technique utilizing microwave frequency modulation, which simplifies high-field measurements by eliminating the need for noisy magnetic field modulation coils.
- Quantum Sensing Potential: The narrow ODMR lines observed in strong fields enable the measurement of these fields with potential sub-micron spatial resolution, crucial for advanced magnetometry.
- Nuclear Spin Access: The resolved 13C HFS components open possibilities for optical detection of Nuclear Magnetic Resonance (NMR) and studies of dynamic nuclear polarization (DNP) in strong fields.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| EPR/ODMR Frequency (High) | 130 | GHz | 2 mm band operation |
| EPR/ODMR Frequency (Low) | 94 | GHz | 3 mm band operation |
| Magnetic Field Range (Tested) | Up to 7 | T | Cryogen-free magneto-optical cryostat |
| Operating Temperature (Cryogenic) | 3, 10 | K | Low-temperature measurements |
| Operating Temperature (High) | 260 | °C | High-temperature ODMR measurements |
| Initial Nitrogen Concentration | ~50 | ppm | HPHT synthetic diamond precursor |
| Final NV- Concentration | 2-3 | ppm | After processing |
| Neutron Irradiation Dose | ~1018 | cm-2 | Defect creation step |
| Zero-Field Splitting (D) | 2.87 | GHz | Fine structure parameter (at 25 °C) |
| ODMR Signal Efficiency | Up to 10 | % | Relative change in PL intensity at resonance |
| 13C Hyperfine Splitting (HFS) | ~20 | mT | Observed in high-field ODMR (Figure 5) |
| 14N Axial Hyperfine (A||) | -2.14 | MHz | Fine structure parameter |
| Magnetic Field Modulation Frequency | 680 | Hz | Standard low-frequency modulation |
| Magnetic Field Modulation Amplitude | 0.1 | mT | Standard modulation amplitude |
Key Methodologies
Section titled “Key Methodologies”The experiments utilized a custom-built, multi-purpose high-frequency spectrometer capable of EPR, ESE, and ODMR measurements in strong magnetic fields.
- Material Synthesis and Processing:
- Monocrystalline synthetic diamonds (HPHT growth) with an initial nitrogen concentration of ~50 ppm were used.
- Samples were irradiated with fast neutrons at a dose of ~1018 cm-2.
- Subsequent annealing was performed in hydrogen gas (~1 h) at 800 °C to form the negative charge state NV- centers (final concentration 2-3 ppm).
- Spectrometer Configuration:
- Measurements were conducted using a 94 GHz (3 mm) and 130 GHz (2 mm) spectrometer integrated with a cryogen-free magneto-optical cryostat providing fields up to ±7 T.
- The sample was mounted to allow rotation around the [110] axis to study orientation dependence.
- Optical Excitation and Detection:
- A 532 nm laser was used for continuous optical excitation and spin polarization.
- Photoluminescence (PL) was collected and detected to monitor the ODMR signal.
- ODMR Measurement Modes:
- Standard Mode: Low-frequency magnetic field modulation (680 Hz, 0.1 mT amplitude) was used for synchronous detection of the magnetic resonance signal.
- Novel Frequency Modulation Mode: A new technique was demonstrated where the microwave frequency (94 GHz) was modulated at low frequency (680 Hz) with a large amplitude (1.4 MHz), simplifying high-field measurements by avoiding magnetic field modulation coils.
- Pulsed Spectroscopy:
- Electron Spin Echo (ESE) spectra were registered using standard two-pulse (π/2 - τ - π - τ - echo) and three-pulse sequences without optical excitation to study spin coherence and relaxation dynamics.
Commercial Applications
Section titled “Commercial Applications”The robust performance of NV centers in strong magnetic fields and cryogenic environments directly supports critical technologies in quantum science and advanced metrology.
- Quantum Computing Hardware: NV centers are leading solid-state qubits. Maintaining high spin polarization and coherence in strong magnetic fields (required for qubit addressing and isolation) is essential for scaling up quantum processors.
- High-Field Quantum Sensing: Enables the development of highly sensitive magnetometers and electrometers capable of operating within superconducting magnets or extreme environments where strong background fields are present.
- Nanoscale Metrology: The narrow ODMR linewidths in high fields allow for magnetic field mapping and sensing with sub-micron spatial resolution, applicable to characterizing magnetic materials and integrated circuits.
- Optical NMR and DNP: The ability to resolve and manipulate nuclear spins (13C) optically in strong fields facilitates the development of optical NMR techniques, potentially enhancing the sensitivity of conventional NMR/MRI systems.
- Localized Thermometry: The temperature dependence of the zero-field splitting (D(T)) allows NV centers to be used as nanoscale thermometers, crucial for monitoring thermal management in microelectronics and biological systems.
- Bio-Sensing and Imaging: Nanodiamonds containing NV centers can be used as robust, non-toxic sensors for biological applications, leveraging the high sensitivity demonstrated across a wide temperature range.
View Original Abstract
Methods of high-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), and optically detectable magnetic resonance (ODMR) were used to study the unique properties of nitrogen-vacancy defects (nitrogen-vacancy NV center) in diamond in strong magnetic fields. It has been shown that in strong magnetic fields (3 to 5 T), an effective optically-induced alignment of populations of spin levels occurs, with filling of the MS=0 level and emptying of the MS=1 levels, which allowed to observe ODMR via variations of the photoluminescence intensity, reaching 10% at resonance. It has been demonstrated that this efficiency in high magnetic fields is of the same order as that in zero and low magnetic fields. The samples were preliminarily studied by ODMR in zero magnetic fields, which made it possible to accurately determine the main parameters of the fine structure and hyperfine interactions with nitrogen nuclei, as well as dipole-dipole interactions between the NV center and deep nitrogen donors (nitrogen atom replacing carbon, N0). In the spectra of high-frequency ODMR, hyperfine interactions with the nearest carbon atoms (13C isotope) were observed, which opens up possibilities for optical measurements of the processes of dynamic nuclear polarization of carbon in strong magnetic fields. Narrow ODMR lines in high magnetic fields are supposed to be used to measure these fields with submicron spatial resolution. A new method for detecting ODMR of NV centers with modulation of the microwave frequency has been developed, which simplifies the technique of measuring high magnetic fields. A significant increase in the intensity of the ODMR signal at orientation of the magnetic field along the symmetry axis of NV center was demonstrated.