Graphene grown out of diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-10-17 |
| Journal | Applied Physics Letters |
| Authors | Changzhi Gu, Wuxia Li, Jing Xu, Shicong Xu, Chao LĂŒ |
| Institutions | University of Chinese Academy of Sciences, Chinese Academy of Sciences |
| Citations | 21 |
| Analysis | Full AI Review Included |
6CCVD Technical Documentation: Graphene Integration via Direct Diamond Epitaxy
Section titled â6CCVD Technical Documentation: Graphene Integration via Direct Diamond EpitaxyâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates a groundbreaking, defect-free method for growing high-quality graphene directly out of a Boron-Doped Single Crystal Diamond (SCD) (111) substrate via MPCVD techniques. This approach solves critical problems associated with traditional graphene transfer or growth on incompatible substrates (e.g., thermal boundary resistance and charge trapping).
- Defect-Free Graphene Synthesis: Spontaneous formation of graphene (monolayer to multilayer) achieved through adequate B-doping density and profile in the diamond lattice, confirmed by the complete absence of the defect-related D peak (1360 cmâ»Âč) in Raman spectroscopy.
- Exceptional Carrier Mobility: Estimated hole Hall mobility for the epitaxial graphene layer reached $1.0767 \times 10^4$ cm2/Vs (10,767 cm2/Vs) in ambient conditions, significantly higher than most reported values for unsuspended graphene.
- Interface Optimization: Direct growth eliminates the substrate contact effect commonly seen in transferred graphene, preserving the intrinsic thermal and electronic properties crucial for high-performance device fabrication.
- Substrate Compatibility Advantage: The method successfully utilized unpolished HPHT SCD (111) substrates with roughness > 100 nm, bypassing the need for expensive, time-consuming ultra-polishing (Ra < 1 nm) required by traditional transfer methods.
- Mechanism Insight: First-principles calculations confirm that B doping, ideally positioned in the 5th layer below the surface, drives the carbon atoms into spontaneous sp2 hybridization, leading to graphene formation bound by weak van der Waals forces.
- Direct Device Integration: This technique allows for the realization of high-performance graphene/diamond heterostructures, ideally suited for electronics requiring unparalleled thermal conductivity (e.g., heat spreaders and thermal interface materials).
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters and performance metrics were achieved in the synthesis of high-quality graphene directly on Boron-Doped Diamond (111) substrates:
| Parameter | Value | Unit | Context / Condition |
|---|---|---|---|
| Graphene Hall Mobility (Estimated) | 1.0767 x 104 | cm2/Vs | Bilayer structure, ambient air conditions |
| B-Doped Diamond Film Thickness (Epitaxial) | 2 | ”m | Formed using HFCVD on SCD (111) |
| Substrate Type | Single Crystal Diamond (SCD) (111) | N/A | HPHT synthesized, unpolished |
| Substrate Roughness (Used) | > 100 | nm | Used successfully, demonstrating transfer-free advantage |
| Growth Temperature (Tsub) | 700 - 900 | °C | Measured by thermocouple |
| Chamber Pressure (P) | 40 - 55 | Torr | Hot-Filament CVD environment |
| Methane Flow (CH4) | 4 | sccm | Carbon precursor gas |
| Hydrogen Flow (H2) | 100 | sccm | Process gas |
| B-Precursor H2 Carrier Flow | 3 - 5 | sccm | Bubbling H2 through B(OCH3)3 liquid |
| Monolayer Growth Duration | 2 | hours | Controlled thickness optimization |
| Raman Shift (Diamond Peak) | 1332 | cm-1 | Strong peak, confirming single crystal quality |
| Raman Shift (Graphene G Peak) | 1584 | cm-1 | E2g phonon mode |
| Raman Shift (Graphene 2D Peak) | 2668 | cm-1 | Primary fingerprint of graphene |
| Defect Peak (D Band) | Absent | N/A | Proving high phase purity (defect-free) |
| Graphene Carrier Concentration (nH1) | 1012 | cm-2 | Bilayer calculation, based on Hall measurement |
| B-Doped Carrier Concentration (nH2) | 1.2 x 1023 | cm-3 | Measured via Hall Effect |
Key Methodologies
Section titled âKey MethodologiesâThe synthesis of high-quality graphene was achieved using a Hot-Filament Chemical Vapor Deposition (HFCVD) system coupled with precise boron doping control:
- Substrate Preparation: Unpolished HPHT Single Crystal Diamond (111) substrates were ultrasonically pretreated in an ethanol solution to clean the surface.
- CVD Setup: HFCVD, a standard method for diamond growth, was employed.
- Process Gases: Methane (CH4) at 4 sccm and Hydrogen (H2) at 100 sccm were used as the primary reaction gases.
- Boron Doping Introduction: Boron was introduced in situ during growth by bubbling H2 carrier gas (3-5 sccm) through a B(OCH3)3 liquid precursor maintained at room temperature.
- Growth Conditions:
- Substrate Temperature: Maintained between 700 °C and 900 °C.
- Chamber Pressure: Maintained between 40 Torr and 55 Torr.
- Epitaxial BDD Film Growth: Deposition duration of 2-3 hours yielded an epitaxial B-doped diamond coating approximately 2 ”m thick.
- Graphene Layer Control: Graphene thickness (monolayer, bilayer, multilayer) was regulated precisely by adjusting the total deposition duration (e.g., 2h for monolayer, 3h for multilayer).
- Characterization: Resulting films were analyzed using micro-Raman spectroscopy (532-nm laser) to confirm defect absence and layer number, and Hall Effect measurements (van der Pauw method) to estimate carrier mobility.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the use of highly controlled Boron-Doped Diamond (BDD) substrates for advanced 2D material integration. 6CCVD specializes in providing the precise MPCVD diamond materials required to replicate and scale this defect-free epitaxial growth technique.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or advance the integration of epitaxial graphene for next-generation devices, 6CCVD recommends the following materials:
| Material Specification | Requirement from Paper | 6CCVD Solution & Benefits |
|---|---|---|
| Single Crystal Diamond (SCD) (111) | Used as the foundation substrate for epitaxial growth. | Electronic Grade SCD (111): Available in high quality for lattice-matched epitaxy, ensuring the required crystal symmetry for spontaneous graphene formation. |
| Boron-Doped Diamond (BDD) | The critical element inducing surface reconstruction and sp2 hybridization. | Heavy Boron Doped SCD/PCD: 6CCVD offers custom-doped BDD films suitable for achieving the specific doping density and profile (e.g., B concentration in the 5th layer) required for this mechanism. |
| Low-Cost Substrate Alternative | Unpolished HPHT SCD used effectively (roughness > 100 nm). | Unpolished or Minimally Polished SCD (111): Since this technique eliminates the need for expensive sub-1 nm polishing (required for transfer methods), 6CCVD can supply cost-effective, readily available substrates to maximize research budgets. |
Customization Potential
Section titled âCustomization PotentialâThe success of direct graphene growth depends on precise material engineering. 6CCVD offers specialized services critical for scaling this technology from research-scale facets to wafer-level devices:
- Custom Dimensions and Substrates: The paper used small facets (200 ”m). 6CCVD provides SCD and PCD wafers up to 125 mm in diameter, enabling scaling to industry-relevant sizes for large-area device fabrication.
- Thickness Control: The experiment utilized a 2 ”m BDD layer. 6CCVD offers precise thickness control for both SCD and PCD layers, ranging from 0.1 ”m up to 500 ”m, and robust substrates up to 10 mm.
- Metalization Services: Although the paper used temporary silver paint contacts, fabrication of high-performance devices requires reliable contacts. 6CCVD offers integrated metalization services (Au, Pt, Pd, Ti, W, Cu) to deposit ohmic or Schottky contacts directly onto the diamond, streamlining the heterostructure device processing.
- Custom Doping Profiles: 6CCVD can engineer MPCVD recipes to achieve specific B-doping density and depth profiles necessary to optimize the spontaneous sp2 hybridization mechanism described by the first-principles calculations.
Engineering Support
Section titled âEngineering SupportâThis research opens promising avenues for high-mobility, thermal-management, and high-frequency electronics. 6CCVDâs in-house team of PhD material scientists and technical engineers can assist customers with:
- Material Selection for Graphene Heterostructures: Consulting on the optimal SCD crystal orientation (e.g., (111) vs. (100)) and doping concentration needed to maximize graphene mobility and thermal boundary resistance (RB) for specific high-power or RF applications.
- Recipe Refinement: Guidance on optimizing HFCVD/MPCVD parameters (gas flow ratios, pressure, temperature) to achieve precise monolayer or bilayer thickness control for quantum electronic applications.
- Thermal Management Solutions: Utilizing the extremely high thermal conductivity of diamond and the low RB achieved by direct growth to develop specialized thermal interface materials and heat spreaders based on graphene-on-diamond layers.
6CCVD supplies the essential foundationâhigh-quality, highly customized MPCVD diamondârequired to translate this breakthrough research into manufacturable high-performance devices.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Most applications of graphene need a suitable support substrate to present its excellent properties. But transferring graphene onto insulators or growing graphene on foreign substrates could cause properties diminishing. This paper reports the graphene growth directly out of diamond (111) by B doping, guided by first-principles calculations. The spontaneous graphene formation occurred due to the reconstruction of the diamond surface when the B doping density and profile are adequate. The resulting materials are defect free with high phase purity/carrier mobility, controllable layer number, and good uniformity, which can be potentially used directly for device fabrication, e.g., high-performance devices requiring good thermal conductivity.