Heat-induced transformation of nickel-coated polycrystalline diamond film studied in situ by XPS and NEXAFS
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-06-12 |
| Journal | Beilstein Journal of Nanotechnology |
| Authors | Olga V. Sedelnikova, Yu. V. Fedoseeva, Dmitriy V. Gorodetskiy, Yuri N. Palyanov, Elena V. Shlyakhova |
| Institutions | Freie Universität Berlin, Siberian Branch of the Russian Academy of Sciences |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Nickel-Catalyzed Graphitization of MPCVD Diamond
Section titled âTechnical Documentation & Analysis: Nickel-Catalyzed Graphitization of MPCVD DiamondâThis document analyzes the research paper âHeat-induced transformation of nickel-coated polycrystalline diamond film studied in situ by XPS and NEXAFSâ to provide technical specifications and align the findings with 6CCVDâs advanced MPCVD diamond capabilities.
Executive Summary
Section titled âExecutive Summaryâ- Catalytic Graphitization: Nickel (Ni) coating successfully promoted the conversion of spÂł diamond surfaces into sp² graphitic carbon layers at significantly reduced temperatures (1100 °C), circumventing the high-temperature requirements (1500-1800 °C) of bare diamond.
- Anisotropic Etching: The study confirmed that Ni-assisted graphitization is highly anisotropic, effectively etching the (110) diamond faces while primarily agglomerating on the (111) faces.
- Material Dependence: Highly ordered graphitic layers (low defect ratio ID/IG = 0.15) were achieved on Ni-coated Single Crystal Diamond (SCD) (110) substrates, whereas Polycrystalline Diamond (PCD) resulted in more structurally disordered sp² carbon films.
- Vertical Orientation: Angle-resolved NEXAFS confirmed that the resulting sp² carbon layers on the annealed Ni-SCD (110) face exhibit a predominantly vertical (upright) orientation relative to the diamond surface (deviation < 5°).
- Application Relevance: This methodology is critical for the controlled fabrication of graphene-on-diamond heterostructures, enabling the integration of thin, conductive electrodes onto dielectric diamond substrates for power electronics and microelectronic devices.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| PCD Film Thickness | 500 | Âľm | Grown by PE CVD |
| SCD Crystal Face Orientation | (110) | N/A | Polished HPHT diamond used for comparison |
| Ni Coating Thickness | 40 | nm | Deposited by thermal evaporation |
| Annealing Temperature (PCD) | 1100 | °C | High-vacuum (10-9 mbar) |
| Annealing Temperature (SCD) | 1150 | °C | High-vacuum (10-9 mbar) |
| Annealing Duration | 15 | min | Time required for surface transformation |
| XPS Probing Depth (830 eV) | ~3 | nm | Surface sensitivity for C 1s spectra |
| NEXAFS Probing Depth (AEY mode) | 3 | nm | Highest surface sensitivity |
| NEXAFS Probing Depth (TEY mode) | 10 | nm | Volume sensitivity |
| ID/IG Ratio (Annealed Ni-SCD) | 0.15 | N/A | Indicates high structural order of sp² layer |
| Graphitic Layer Orientation | Vertical (Upright) | N/A | Relative to SCD (110) face (deviation < 5°) |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on precise MPCVD synthesis, controlled metal deposition, and advanced in situ synchrotron analysis:
- Diamond Synthesis:
- PCD films (500 Âľm thick) were produced via Plasma-Enhanced Chemical Vapor Deposition (PE CVD) using an acetone/hydrogen/air mixture.
- Synthetic SCD crystals were grown via the High-Pressure High-Temperature (HPHT) method and polished to obtain the specific (110) crystal face.
- Nickel Coating:
- A thin nickel film (40 nm thick) was deposited onto both PCD and SCD substrates using a thermal evaporation method.
- High-Vacuum Annealing:
- Samples were annealed simultaneously in ultrahigh vacuum (10-9 mbar) at 1100 °C (PCD) or 1150 °C (SCD) for 15 minutes to induce catalytic graphitization.
- Synchrotron Characterization (In Situ):
- X-ray Photoelectron Spectroscopy (XPS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) were performed at the BESSY II synchrotron facility without breaking the ultrahigh vacuum.
- NEXAFS spectra were recorded in Total Electron Yield (TEY, 10 nm depth) and Auger Electron Yield (AEY, 3 nm depth) modes for complementary volume and surface analysis.
- Angle-resolved NEXAFS was used on Ni-SCD (110) to determine the spatial orientation of the formed sp² carbon layers.
- Post-Annealing Analysis (Ex Situ):
- Scanning Electron Microscopy (SEM) and Raman spectroscopy (514 nm laser, 1 Âľm spot size) were used to analyze the morphology and structural quality of the graphitic layers.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for high-quality, precisely oriented diamond substrates and controlled metal deposition for advanced carbon heterostructure fabrication. 6CCVD is uniquely positioned to supply the materials and engineering services required to replicate and extend this work.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the highly ordered, vertically oriented graphitic layers demonstrated in the paper, researchers require the highest quality substrates:
- Optical Grade SCD (110) & (100): Essential for replicating the low-defect (ID/IG = 0.15) sp² carbon layers. 6CCVD provides SCD with precise crystallographic orientation control, crucial for exploiting the anisotropic etching behavior of nickel.
- Polycrystalline Diamond (PCD) Wafers: Ideal for cost-effective, large-area production of conductive films. 6CCVD supplies high-quality PCD plates up to 125mm in diameter, significantly larger than the micron-sized crystallites studied.
- Custom Substrate Thickness: We offer SCD and PCD plates ranging from 0.1 Âľm to 500 Âľm, and robust substrates up to 10 mm thick, matching the dimensional requirements of the study.
Customization Potential
Section titled âCustomization PotentialâThe success of this research hinges on the precise control of the catalytic layer and substrate geometry. 6CCVD offers comprehensive customization services:
| Research Requirement | 6CCVD Customization Service | Benefit to Researcher |
|---|---|---|
| Catalytic Layer Deposition | Custom Metalization (Ni, Ti, Pt, Au, Pd, W, Cu): We offer internal metal deposition capabilities, allowing precise control over the thickness (e.g., 40 nm Ni) and uniformity of the catalytic film. | Enables rapid iteration on catalytic material selection and thickness optimization for graphitization kinetics. |
| Large-Area Processing | PCD Wafers up to 125mm: We can scale the substrate size significantly beyond typical lab samples, facilitating the transition from research to pilot production for power devices. | Supports industrial scale-up of graphene-on-diamond heterostructures. |
| Surface Preparation | Ultra-Low Roughness Polishing: We provide SCD polishing to Ra < 1 nm and inch-size PCD polishing to Ra < 5 nm. | Minimizes intrinsic structural defects and surface roughness, which the paper noted increases layer defectiveness in fine-dispersed crystallites. |
| Geometry and Shape | Precision Laser Cutting: Custom shapes and dimensions can be provided to fit specific experimental setups (e.g., synchrotron end-stations or device integration). | Ensures seamless integration into complex experimental or device architectures. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists specializes in MPCVD diamond growth and surface functionalization. We offer expert consultation for projects involving:
- Graphene-on-Diamond Heterostructures: Assistance in selecting the optimal diamond material (SCD vs. PCD) and orientation ((110) vs. (100)) to control graphitic layer order and orientation (e.g., achieving the desired vertical sp² orientation).
- Catalytic Surface Chemistry: Guidance on precursor selection and deposition parameters for metal-assisted graphitization processes.
- Advanced Characterization: Support in interpreting material properties relevant to XPS, NEXAFS, and Raman data.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Controlling high-temperature graphitization of diamond surfaces is important for many applications, which require the formation of thin conductive electrodes on dielectric substrates. Transition metal catalysts can facilitate the graphitization process, which depends on the diamond face orientation. In the present work, the role of a nickel coating on the electronic structure and chemical state of graphite layers formed on the surface of a polycrystalline diamond (PCD) film with mixed grain orientation was studied. A synthetic single-crystal diamond (SCD) with a polished (110) face was examined for comparison. The samples were coated with a thin nickel film deposited by thermal evaporation. The graphitization of diamond with and without a nickel coating as a result of high-vacuum annealing at a temperature of about 1100 °C was studied in situ using synchrotron-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) methods. XPS data revealed the formation of a thin graphite-like film with low-ordered atomic structure on the surface of the nickel-coated PCD film. The chemical state of sp 2 -hybridized carbon atoms was found to be insensitive to the face orientation of the diamond micro-sized crystallites; however, the layer defectiveness increased in areas with fine-dispersed crystallites. According to NEXAFS and Raman spectroscopy data, the most ordered atomic structure of graphitic layers was obtained by annealing nickel-coated SCD. The angular dependence of NEXAFS C K-edge spectra of nickel-coated (110) face after annealing discovered the vertical orientation of sp 2 -hybridized carbon layers relative to the diamond surface. The observed behavior suggests that sp 2 carbon layers were formed on the diamond surface due to its saturation by released carbon atoms as a result of etching by nickel.