Enhanced Optical 13 C Hyperpolarization in Diamond Treated by High‐Temperature Rapid Thermal Annealing
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-09-09 |
| Journal | Advanced Quantum Technologies |
| Authors | Max Gierth, Valentin Krespach, Alexander I. Shames, Priyanka Raghavan, Emanuel Druga |
| Institutions | City College of New York, College of Staten Island |
| Citations | 13 |
| Analysis | Full AI Review Included |
High Temperature Annealing Enhanced Diamond 13C Hyperpolarization: Technical Analysis and 6CCVD Solutions
Section titled “High Temperature Annealing Enhanced Diamond 13C Hyperpolarization: Technical Analysis and 6CCVD Solutions”This document analyzes the findings of the research paper “High temperature annealing enhanced diamond 13C hyperpolarization at room temperature” and outlines how 6CCVD’s advanced MPCVD diamond materials and processing capabilities can support and extend this critical research in quantum materials and biomedical imaging.
Executive Summary
Section titled “Executive Summary”The research demonstrates a breakthrough in optimizing diamond materials for Dynamic Nuclear Polarization (DNP), achieving unprecedented levels of 13C hyperpolarization at room temperature through specialized High-Temperature Annealing (HTA).
- Record Enhancement: Achieved up to a 36-fold increase in 13C hyperpolarization enhancement (ε) compared to conventionally annealed (850°C) diamond particles.
- Optimal Processing: The maximum gain was realized using HTA at 1720°C for 15 minutes, demonstrating that post-growth thermal treatment is the dominant factor in maximizing DNP efficiency.
- Lattice Healing Mechanism: HTA effectively heals radiation-induced lattice disorder, leading to a significant reduction in adverse paramagnetic impurities (e.g., W33, W16-W18 triplet defects).
- Spin Lifetime Improvement: The lattice healing resulted in a 10x increase in the NV electron spin-lattice relaxation time (T1e) and a 3-5x increase in the 13C nuclear relaxation lifetime (T1).
- Material Performance: The optimized material achieved a bulk 13C polarization level of ~0.3%, the highest reported optical hyperpolarization level on crushed particles <20µm in size.
- Multimodal Application: The HTA process also endows the particles with multicolor fluorescence (NV, H3, N3 centers), making them ideal candidates for multi-modal (Optical/MRI) imaging and quantum sensing applications.
Technical Specifications
Section titled “Technical Specifications”The following table summarizes the key quantitative parameters and performance metrics extracted from the study, focusing on the optimal HTA conditions.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum DNP Enhancement (ε) | 36 | fold | Achieved at 1720°C HTA (15 min) vs. 850°C standard annealing. |
| Optimal HTA Temperature | 1720 ± 10 | °C | Annealing condition for peak performance. |
| Optimal HTA Duration | 15 | min | Annealing time at 1720°C. |
| Bulk 13C Polarization Level | ~0.3 | % | Highest reported optical hyperpolarization on <20µm particles. |
| Polarization Magnetic Field (Bpol) | ~38 | mT | Optimal field for DNP transfer. |
| Detection Magnetic Field (Bdet) | 7 | T | High-field NMR readout. |
| NV Electron T1e Increase | ~10 | fold | Compared to 850°C annealed samples. |
| 13C Nuclear T1 Increase | 3-5 | fold | Result of HTA-driven lattice healing. |
| Particle Size Studied | 18 ± 3 | µm | Type Ib HPHT diamond microparticles. |
| Total Nitrogen Content | ~100 | ppm | Starting material specification. |
| Optimal Electron Fluence (D2) | 5 x 1019 | e/cm2 | Electron irradiation dose for the 36x enhanced sample. |
| NV- Concentration (Optimal HTA) | ~7 | ppm | Concentration preserved after 1720°C HTA. |
Key Methodologies
Section titled “Key Methodologies”The experimental success hinges on precise control over defect creation (irradiation) and subsequent lattice healing (HTA). The following steps outline the critical material processing and characterization techniques used:
- Starting Material Preparation: Type Ib HPHT diamond particles (~100ppm total nitrogen) were milled to a uniform size of 18µm ± 3µm.
- Defect Generation: Samples were subjected to controlled electron irradiation (fluence up to 5 x 1019 e/cm2) to create vacancies necessary for NV center formation.
- Standard Annealing: Conventional NV formation annealing was performed at 850°C for 2 hours.
- High-Temperature Annealing (HTA): Samples were treated in an all-graphite furnace (Model HTT-G10) under precise temperature control (1200°C to 1800°C), typically using a hydrogen atmosphere. The optimal condition was 1720°C for 15 minutes.
- DNP Setup: Room temperature optical DNP was performed using a 9-laser system (520 nm, ~570mW/mm2 excitation density) arranged in an octagonal pattern under a 38mT polarizing field.
- Polarization Transfer: Chirped microwave (MW) irradiation (~2.5mW/mm3 density) was applied synchronously with laser excitation to transfer polarization to the 13C lattice via rotating frame Landau-Zener transitions.
- Characterization: Hyperpolarized 13C NMR signals were detected at 7T. Electron Paramagnetic Resonance (EPR) spectroscopy and NMR relaxometry (mapping R1(B)) were used to quantify defect concentrations (NV-, P1, W33) and relaxation times (T1, T1e).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The research highlights that the ultimate performance of diamond hyperpolarization agents is dictated by superior lattice quality and precise defect engineering—areas where 6CCVD’s MPCVD capabilities provide a distinct advantage over traditional HPHT materials.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage for Replication/Extension |
|---|---|---|
| Ultra-High Purity Material (Required for long T1/T1e) | Optical Grade Single Crystal Diamond (SCD): Grown via MPCVD, offering extremely low native defect density and superior crystalline quality. | Provides the ideal starting platform for maximizing NV electron T1e and 13C nuclear T1 lifetimes, surpassing the performance limits of Type Ib HPHT materials. |
| Bulk Material for Milling (Need large source for micro/nanoparticles) | Polycrystalline Diamond (PCD) Wafers up to 125mm: Available in thicknesses up to 500µm, or SCD substrates up to 10mm thick. | Enables large-scale, cost-effective production of high-quality diamond material suitable for bulk irradiation and subsequent milling into hyperpolarization agents. |
| Precise Defect Engineering (Control over N content and vacancy creation) | Custom Doping and Irradiation Control: Nitrogen concentration can be precisely controlled during MPCVD growth. We offer tailored post-processing protocols, including electron irradiation and advanced high-temperature annealing (HTA) support. | Allows researchers to optimize the NV- concentration (e.g., 4-7 ppm) while ensuring the lattice is healed to minimize paramagnetic leakage pathways. |
| Custom Dimensions (Specific particle sizes needed) | Custom Laser Cutting and Shaping: We provide plates and wafers cut to custom dimensions and geometries prior to milling. | Supports the creation of specific particle sizes (microparticles or nanodiamonds) required for in-vivo or liquid-phase DNP applications. |
| Integration into Devices (Potential for surface spin relay) | In-House Metalization Services: Capability to deposit Au, Pt, Pd, Ti, W, and Cu contacts. | Essential for integrating diamond materials into microfluidic or sensing devices, facilitating the proposed spin polarization relay channels to external liquids. |
| Surface Quality (Critical for surface functionalization) | Advanced Polishing Services: SCD (Ra < 1nm) and Inch-size PCD (Ra < 5nm). | Ensures optimal surface quality for subsequent chemical functionalization, crucial for targeting and efficient spin transfer in liquid environments. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team specializes in defect engineering and high-temperature post-processing optimization. We offer consultation services to assist researchers in selecting the optimal MPCVD material (SCD or PCD) and developing precise thermal recipes to replicate or extend the HTA protocols (up to 1800°C) for similar MRI/DNP Hyperpolarization projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Methods of optical dynamic nuclear polarization open the door to the replenishable hyperpolarization of nuclear spins, boosting their nuclear magnetic resonance/imaging signatures by orders of magnitude. Nanodiamond powder rich in negatively charged nitrogen vacancy defect centers has recently emerged as one such promising platform, wherein 13 C nuclei can be hyperpolarized through the optically pumped defects completely at room temperature. Given the compelling possibility of relaying this 13 C polarization to nuclei in external liquids, there is an urgent need for the engineered production of highly “hyperpolarizable” diamond particles. Here, a systematic study of various material dimensions affecting optical 13 C hyperpolarization in diamond particles is reported on. It is discovered surprisingly that diamond annealing at elevated temperatures ∼1720 °C has remarkable effects on the hyperpolarization levels enhancing them by above an order of magnitude over materials annealed through conventional means. It is demonstrated these gains arise from a simultaneous improvement in NV − electron relaxation/coherence times, as well as the reduction of paramagnetic content, and an increase in 13 C relaxation lifetimes. This work suggests methods for the guided materials production of fluorescent, 13 C hyperpolarized, nanodiamonds and pathways for their use as multimodal (optical and magnetic resonance) imaging and hyperpolarization agents.