Boron nitride for excitonics, nano photonics, and quantum technologies
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-06-29 |
| Journal | Nanophotonics |
| Authors | Bernard Gil, Guillaume Cassabois, R. CuscĂł, Giorgia Fugallo, LluĂs ArtĂșs |
| Institutions | Centre National de la Recherche Scientifique, Laboratoire Charles Coulomb |
| Citations | 50 |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Boron Nitride for Quantum Technologies and DUV Applications
Section titled âTechnical Analysis & Documentation: Boron Nitride for Quantum Technologies and DUV ApplicationsâSource Paper: Boron nitride for excitonics, nano photonics, and quantum technologies (Nanophotonics 2020; 9(11): 3483-3504)
Executive Summary
Section titled âExecutive SummaryâThis paper thoroughly reviews Hexagonal Boron Nitride (hBN) capabilities across three high-growth technical domains, positioning hBN as a direct competitor and complementary material to diamond, particularly in quantum and DUV applications.
- Quantum Technology Challenge: hBN defects are actively studied for their propensity to function as Single Photon Emitters (SPSs) in the 1.5 eV to 4 eV range, posing a challenge to established solid-state qubits like NV centers in diamond and double vacancies in SiC.
- Deep Ultraviolet (DUV) Performance: hBN is highlighted for intrinsic DUV emission at 215 nm, promising compact, high-efficiency emitters necessary for sanitary applications (virus and bacteria killing) across the critical 200-300 nm wavelength range.
- Nanophotonics and Thermal Management: The material exhibits hyperbolic phonon polaritons in the mid-infrared (6 ”m and 12 ”m Reststrahlen bands), enabling hyper-lensing and nanophotonic management. Simultaneously, hBN possesses highly anisotropic, high thermal conductivity, making it an excellent candidate for thermal management substrates.
- Exciton-Phonon Coupling: The unusually strong efficiency of exciton-phonon coupling facilitates light emission from this indirect band gap semiconductor, leading to high internal quantum efficiency (reported 50% at room temperature).
- Isotopic Engineering: Studies confirm that isotopic purification (specifically 10B) significantly impacts thermal conductivity and sharpens phonon lifetimes, which is crucial for achieving high-quality factor polariton devices.
- Relevance to 6CCVD: The intense focus on hBN as a quantum emitter directly validates the market for high-purity Single Crystal Diamond (SCD), which offers superior qubit coherence, stability, and established industrial application, complementing hBNâs DUV potential.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes key performance metrics and material parameters derived from the analysis of hexagonal boron nitride (hBN).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| DUV Emission Wavelength (Laser Action) | 215 | nm | Measured in bulk hBN single crystals (Ref. 16) |
| Forbidden Indirect Exciton Energy | 5.955 | eV | High-energy transition, replicated by phonon replicas |
| Exciton-Phonon Coupling Efficiency | 50 | % | Internal Quantum Efficiency (IQE) at Room Temperature (RT) |
| Lower Reststrahlen Band | 784-819 | cm-1 | Corresponds to â12 ”m wavelength, Type I hyperbolic polaritons |
| Upper Reststrahlen Band | 1367-1607 | cm-1 | Corresponds to â6 ”m wavelength, Type II metallic response |
| High Frequency Raman Mode ($E_{2g}$) | 1369 | cm-1 | Measured in natBN at 77 K |
| Low Frequency Raman Mode ($E_{2g}$) | 52.7 | cm-1 | Measured in natBN at 77 K (Interlayer gliding motion) |
| SPS Emission Energy Range (Defects) | 1.5 - 4 | eV | Broad spectral range of defects acting as single photon sources |
| In-Plane Thermal Conductivity ($k_{ | }$) | â850 | |
| Out-of-Plane Thermal Conductivity ($k_{\perp}$) | â10 | W·m-1·K-1 | Measured at 300 K (highly anisotropic) |
| Band Gap (Bulk) | Indirect | N/A | Band gap is indirect between M and K points |
Key Methodologies
Section titled âKey MethodologiesâThe research utilizes highly specialized material growth and characterization techniques critical for developing hBN technology, mirroring processes used in advanced diamond growth (MPCVD).
Material Synthesis and Conditioning
Section titled âMaterial Synthesis and Conditioningâ- Bulk Single Crystal Growth: Large size hBN single crystals (1 x 1 x 0.2 mm3) were grown using high-temperature, high-pressure solidification from metallic flux (e.g., Fe-Cr flux, Ba-BN solvent) to maximize purity and crystal size.
- Epitaxial Layer Growth: Production of high-quality monolayer and few-layer hBN films using advanced deposition techniques (MOCVD, MBE) on target substrates (e.g., sapphire, highly ordered pyrolytic graphite, metal foils).
- Isotopic Purification: Synthesis of hBN using mono-isotopically enriched boron precursors (10B and 11B) to study anharmonic phonon decay channels and enhance phonon lifetime and thermal transport properties.
Characterization and Spectroscopy
Section titled âCharacterization and Spectroscopyâ- Optoelectronic Measurements: Cathodoluminescence (CL) and low-temperature photoluminescence (PL) spectroscopy (down to 8 K) to identify DUV emission (215 nm) and analyze complex exciton-phonon replicas (5.65-6.0 eV range).
- Phonon and Lattice Analysis: High-resolution Raman scattering and Infrared (IR) reflectivity measurements used to determine phonon energies (e.g., $E_{2g}$ modes) and analyze the dielectric constant components ($\epsilon_{xx}$, $\epsilon_{zz}$) revealing hyperbolic dispersion relations.
- Thermal and Structural Analysis: Temperature-dependent Raman scattering and ab initio calculations (Boltzmann Transport Equation, BTE) were used to quantify anisotropic thermal conductivity and study phonon anharmonicity.
- Defect Characterization: Use of micro-PL and second-order correlation functions ($g^{2}(t)$) to isolate and characterize individual single photon emitters (SPSs) related to specific lattice defects (e.g., boron vacancy $V_{B}$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research validates a strong and growing market for materials providing extreme performance in DUV, thermal management, and quantum computing. 6CCVDâs specialized MPCVD diamond offerings provide necessary complementary and superior performance materials to replicate, integrate, and advance this research.
Addressing the Quantum Qubit Challenge (hBN vs. Diamond NV Centers)
Section titled âAddressing the Quantum Qubit Challenge (hBN vs. Diamond NV Centers)âWhile hBN defects show promise as SPSs, the field of quantum computing relies on robust, stable, and highly coherent qubits. 6CCVD Single Crystal Diamond (SCD), manufactured with superior purity and defect control, remains the gold standard.
| hBN Application/Challenge | 6CCVD Diamond Solution | Technical Advantage |
|---|---|---|
| SPS Emitter: hBN defects (4.0-1.5 eV) | High-Purity SCD Wafers: Tailored for N-V or Si-V center creation. | Superior Coherence: NV centers offer millisecond coherence times (unavailable in current hBN SPSs). |
| Material Purity/Disorder: Isotopic disorder limits hBN phonon lifetimes. | Isotopically Purified 12C SCD: Ultra-low nitrogen content ([N] < 1 ppb) and high isotopic purity optimize spin coherence and minimize decoherence. | Coherence & Stability: Extends qubit lifetime necessary for practical quantum applications. |
| Integration/Substrates: Need for robust, high-performance platform integration. | Large Format SCD/PCD: Wafers up to 125 mm (PCD) and highly polished SCD (Ra < 1 nm) substrates. | Heterostructure Support: Provides ultra-smooth, thermally stable platforms for complex hybrid devices. |
Applicable 6CCVD Materials for DUV and Nanophotonic Research
Section titled âApplicable 6CCVD Materials for DUV and Nanophotonic ResearchâTo replicate or extend the advanced DUV and nanophotonic concepts explored in this paper, 6CCVD recommends materials that exploit diamondâs extreme properties:
- Optical Grade SCD: Essential for DUV studies (light extraction/transmission at < 220 nm) where diamond offers the widest transmission window of any known solid material. Ideal for use as DUV lenses or windows integrated with hBN emitters.
- Heavy Boron Doped PCD (BDD): Useful for creating plasmonic and conducting layers in nanophotonic devices. While hBN polaritons operate in the IR, BDD can be engineered to generate surface plasmons in different spectral ranges, complementing hBNâs capabilities.
- Thermal Management Substrates: SCD/PCD substrates (up to 10 mm thick) offer thermal conductivity far exceeding that of hBNâs out-of-plane value ($k_{\perp} \approx 10$ W·m-1·K-1). Use 6CCVD diamond to manage heat dissipation in high-power DUV emitter designs.
Customization Potential for Device Integration
Section titled âCustomization Potential for Device IntegrationâThe synthesis of complex heterostructures (like hBN-graphene) and the creation of targeted defects (SPSs) necessitates high precision engineering:
- Custom Dimensions and Etching: 6CCVD offers laser cutting and precision processing for both SCD and PCD wafers up to 125 mm in diameter, allowing researchers to obtain unique geometries required for hyper-lensing and specific photonic structures.
- Metalization Services: The paper implies the need for complex device structures involving electrical contacts. 6CCVD provides in-house metalization capabilities, including deposition of Au, Pt, Pd, Ti, W, and Cu layers, crucial for creating ohmic contacts or waveguides in hBN/Diamond hybrid systems.
- Ultra-High Polishing: 6CCVD achieves surface roughness down to Ra < 1 nm on SCD, critical for minimizing scattering and maximizing efficiency in DUV optoelectronics and nanophotonic resonators.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team provides specialized consultation for projects requiring extreme materials science. We assist engineers and scientists in selecting optimal diamond types (SCD, PCD, BDD) and specifications (thickness, doping, orientation, metalization) to achieve superior performance in DUV light management, high-heat flux thermal dissipation, and next-generation solid-state quantum projects.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract We review the recent progress regarding the physics and applications of boron nitride bulk crystals and its epitaxial layers in various fields. First, we highlight its importance from optoelectronics side, for simple devices operating in the deep ultraviolet, in view of sanitary applications. Emphasis will be directed towards the unusually strong efficiency of the exciton-phonon coupling in this indirect band gap semiconductor. Second, we shift towards nanophotonics, for the management of hyper-magnification and of medical imaging. Here, advantage is taken of the efficient coupling of the electromagnetic field with some of its phonons, those interacting with light at 12 and 6 ”m in vacuum. Third, we present the different defects that are currently studied for their propensity to behave as single photon emitters, in the perspective to help them becoming challengers of the NV centres in diamond or of the double vacancy in silicon carbide in the field of modern and developing quantum technologies.