Large microwave inductance of granular boron-doped diamond superconducting films
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-06-14 |
| Journal | Applied Physics Letters |
| Authors | Bakhrom Oripov, Dinesh Kumar, Cougar Garcia, Patrick Hemmer, T. Venkatesan |
| Institutions | National University of Singapore, University of Maryland, College Park |
| Citations | 5 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High Kinetic Inductance Boron-Doped Diamond
Section titled âTechnical Documentation & Analysis: High Kinetic Inductance Boron-Doped DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research validates the use of granular Boron-Doped Diamond (BDD) thin films as a high-kinetic inductance (Lk) material, critical for next-generation quantum devices and detectors. 6CCVDâs MPCVD capabilities are ideally suited to replicate and optimize these structures.
- High Kinetic Inductance: Granular BDD films exhibit unusually large microwave kinetic inductance, making them prime candidates for Microwave Kinetic Inductance Detectors (MKIDs) and high-impedance quantum circuits.
- Granularity Confirmed: The measured zero-temperature magnetic penetration depth ($\lambda(0) \approx 2.19$ ”m) is significantly larger than theoretical estimates, confirming the strong granular nature necessary for high Lk performance.
- Superconducting Performance: The material demonstrates a high critical temperature (Tc up to 7.2 K onset) and exhibits full s-wave superconducting behavior consistent with BCS theory, despite the granular microstructure.
- Performance Enhancement: The study notes that decreasing film thickness substantially enhances the self-Kerr coefficient (nonlinearity), a key metric for quantum applications. 6CCVD offers precise thickness control down to 0.1 ”m.
- Methodology: The Parallel Plate Resonator (PPR) technique was successfully employed to measure the in-plane complex surface impedance without requiring direct electrical contacts.
- 6CCVD Advantage: 6CCVD specializes in MPCVD Polycrystalline Diamond (PCD) and BDD films, offering superior control over grain size and doping concentration required to engineer optimal disorder and maximize kinetic inductance.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the analysis of Film âAâ and related measurements, demonstrating the materialâs superconducting properties.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal Critical Temperature (Tc) | 7.2 | K | DC Onset Measurement |
| Fitted Critical Temperature (Tc) | 6.717 ± 0.001 | K | PPR Fit using Eq. (1) |
| Zero-Temperature Penetration Depth ($\lambda(0)$) | 2.189 ± 0.006 | ”m | PPR Fit (Large value due to granularity) |
| Superconducting Gap ($\Delta(0)$) | 924.38 ± 76.60 | ”eV | Low-Temperature Fit using Eq. (2) |
| Gap Ratio ($\Delta(0)$/kBTc) | 1.597 | Dimensionless | Close to weak-coupled BCS limit (1.76) |
| Normal State Resistivity ($\rho_n$) | 2.32 ± 0.31 | mΩ cm | Estimated from Normal State Surface Resistance (RN) |
| Film Thickness (t) | 1.5 | ”m | Cross-sectional Electron Microscopy |
| Hall Concentration (nh) | 3.0 x 1021 | cm-3 | Measured on Film A |
| Self-Kerr Coefficient (K11) | 15.25 | mHz/photon | Measured on Film B at 100 mK |
| Dielectric Spacer Thickness (d) | 75 or 430 | ”m | Sapphire (PPR setup) |
Key Methodologies
Section titled âKey MethodologiesâThe BDD films were synthesized using Hot Filament Chemical Vapor Deposition (HFCVD) to achieve the necessary high boron concentration and granular structure.
- Deposition Technique: Hot Filament Chemical Vapor Deposition (HFCVD) was used, resulting in granular (nanocrystalline) BDD films.
- Substrate Preparation: Silicon substrates were used, likely diamond-seeded to promote nucleation.
- Temperature and Pressure: The substrate temperature was maintained at 850 °C, and the chamber pressure was approximately 7 Torr.
- Gas Composition:
- Methane (CH4): 80 sccm
- Hydrogen (H2): 3000 sccm
- Boron Source (B(CH3)3): Flow rate adjusted to achieve a B/C ratio of approximately 10,000 ppm.
- Measurement Technique: The in-plane complex surface impedance was measured using a Parallel Plate Resonator (PPR) technique, capacitively coupled via coaxial cables, cooled in a dilution refrigerator (T = 25 mK to Tc).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced diamond materials required to replicate and extend this high-kinetic inductance research, particularly for applications in quantum computing and high-sensitivity detection.
Applicable Materials
Section titled âApplicable MaterialsâThe high kinetic inductance observed is directly linked to the granular microstructure and high boron doping. 6CCVDâs MPCVD process offers superior control over these parameters compared to the HFCVD method used in the paper.
- Heavy Boron Doped Polycrystalline Diamond (BDD-PCD): This is the ideal material. 6CCVD can engineer the specific grain size and disorder required to maximize the magnetic penetration depth ($\lambda$) and kinetic inductance (Lk), replicating the desirable granular nature of the NCD films studied.
- Ultra-Thin BDD Films: The research indicates that reducing film thickness enhances the self-Kerr coefficient (nonlinearity). 6CCVD offers BDD films with precise thickness control from 0.1 ”m up to 500 ”m, allowing researchers to optimize Lk and nonlinearity for specific device designs (e.g., compact resonators or quantum circuits).
Customization Potential
Section titled âCustomization PotentialâThe success of high-inductance devices relies heavily on precise geometry and integration. 6CCVD provides comprehensive customization services to meet these demands:
| Requirement from Paper/Application | 6CCVD Capability | Specification |
|---|---|---|
| Film Dimensions | Custom Plates/Wafers | Up to 125 mm (PCD) |
| Film Thickness (t) | Ultra-precise control | SCD/PCD from 0.1 ”m to 500 ”m |
| Substrate Integration | Custom Substrates | Substrates up to 10 mm thickness |
| Device Integration | Custom Metalization | In-house deposition of Au, Pt, Pd, Ti, W, Cu |
| Surface Quality | Low-loss Polishing | Ra < 5 nm (Inch-size PCD) for optimal resonator performance |
Specific Note on Metalization: While the PPR measurement is contact-free, future quantum impedance devices (e.g., Josephson junctions, as referenced in the paper) require robust electrical contacts. 6CCVD offers custom metalization stacks (e.g., Ti/Pt/Au) tailored for superconducting diamond interfaces.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers specializes in optimizing MPCVD diamond for quantum applications.
- Disorder Engineering: We assist researchers in tuning the MPCVD growth parameters (pressure, temperature, gas ratios) to control the grain size and boundary density, thereby optimizing the disorder necessary to achieve maximum kinetic inductance and Tc in BDD films.
- Material Selection for MKIDs: Our team provides consultation on selecting the optimal BDD doping level and thickness required to achieve specific resonant frequencies and quality factors (Q) for Microwave Kinetic Inductance Detectors (MKIDs) projects.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive diamond materials directly to your research facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Boron-doped diamond granular thin films are known to exhibit superconductivity with an optimal critical temperature of Tc=7.2 K. Here, we report the measured in-plane complex surface impedance of boron-doped diamond films in the microwave frequency range using a resonant technique. Experimentally measured inductance values are in good agreement with estimates obtained from the normal state sheet resistance of the material. The magnetic penetration depth temperature dependence is consistent with that of a fully gapped s-wave superconductor. Boron-doped diamond films should find application where high kinetic inductance is needed, such as microwave kinetic inductance detectors and quantum impedance devices.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2005 - Origin of the metallic properties of heavily boron-doped superconducting diamond [Crossref]
- 2012 - Vertical SNS weak-link Josephson junction fabricated from only boron-doped diamond [Crossref]
- 2010 - Superconductivity in diamond [Crossref]
- 2004 - Dependence of the superconducting transition temperature on the doping level in single-crystalline diamond films [Crossref]
- 2004 - Superconductivity in diamond thin films well above liquid helium temperature [Crossref]
- 2018 - Tc suppression and impurity band structure in overdoped superconducting boron-doped diamond films [Crossref]
- 2008 - Constraints on Tc for superconductivity in heavily boron-doped diamond [Crossref]
- 2020 - High-temperature conventional superconductivity in the boron-carbon system: Material trends [Crossref]
- 2017 - Discovery of high-temperature superconductivity (tc = 55 k) in b-doped q-carbon [Crossref]
- 2018 - Isatin detection using a boron-doped diamond 3-in-1 sensing platform [Crossref]