Elastic and mechanical softening in boron-doped diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-02-24 |
| Journal | Scientific Reports |
| Authors | Xiaobing Liu, YunâYuan Chang, Sergey N. Tkachev, Craig R. Bina, Steven D. Jacobsen |
| Institutions | Northwestern University, University of Chicago |
| Citations | 19 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Elastic and Mechanical Softening in Boron-Doped Diamond
Section titled âTechnical Documentation and Analysis: Elastic and Mechanical Softening in Boron-Doped DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research establishes critical data regarding the mechanical and elastic properties of heavily boron-doped single-crystal diamond (BDD), revealing significant mechanical softening relevant to ultrahard materials science and semiconductor applications.
- Core Finding: Single-crystal BDD experiences a drastic elastic and mechanical softening when boron concentration exceeds 2000 ppm, relative to low-doped diamond (50-300 ppm).
- Mechanical Degradation: Vickers hardness ($H_v$) drops by approximately 15% in high-doped regions, moving from $118 \pm 3 \text{ GPa}$ (low BDD) to $100 \pm 2 \text{ GPa}$ (2000-3000 ppm BDD).
- Elastic Softening: Both the Shear Modulus ($G_0$) and elastic constants ($C_{ij}$) are systematically reduced by up to 3% in highly doped BDD, confirming a trend toward more ductile behavior.
- Advanced Metrology: Accurate hardness quantification in the ultrahard region (H$_v$ > 80 GPa) was achieved using high-precision GHz-ultrasonic interferometry combined with 3D optical microscopy to overcome ambiguity caused by brittle cracking near indentations.
- Application Relevance: The study provides fundamental elasticity-hardness correlations crucial for designing novel ultrahard abrasives, as well as BDD materials for extreme environment semiconductor and power electronic applications.
- Methodology: HPHT synthesis was used to create BDD crystals with continuous compositional gradients, allowing localized mapping of properties across a wide doping range (50-3000 ppm).
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters were extracted from the investigation of single-crystal boron-doped diamond (BDD-D4).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max Boron Concentration | 3000 | ppm | Highest doping region studied (BDD-2) |
| Vickers Hardness (H$_v$) | 100 ± 2 | GPa | High BDD (2000-3000 ppm B) |
| Vickers Hardness (H$_v$) | 118 ± 3 | GPa | Low BDD (50-300 ppm B) |
| Single Crystal Orientation | (110) | N/A | Primary plane studied for $H_v$ and elasticity |
| Sample Thickness | 0.185 | mm | (110) Section thickness |
| Shear Modulus (G$_0$) | 517.1 ± 5.4 | GPa | High BDD (2000-3000 ppm B) |
| Bulk Modulus (K$_s$) | 431.2 ± 9.6 | GPa | High BDD (2000-3000 ppm B) |
| Elastic Constant (C11) | 1049.5 ± 9.6 | GPa | High BDD (2000-3000 ppm B) |
| Density ($\rho$) | 3503 ± 1 | kg/m3 | High BDD (2000-3000 ppm B) |
| Indentation Load Range | 0.1 to 10 | N | Used for Vickers Hardness testing |
| Synthesis Conditions (T) | ~1380 | °C | Temperature Gradient Growth |
| Synthesis Conditions (P) | 5.5 | GPa | HPHT synthesis pressure |
Key Methodologies
Section titled âKey MethodologiesâThe experiment successfully characterized the mechanical and elastic properties of BDD through the following integrated techniques:
- HPHT Synthesis: Single-crystal BDD was synthesized using the temperature gradient growth method at 5.5 GPa and up to 1380 °C, utilizing a Kovar alloy (Fe${54}$Ni${29}$Co$_{17}$) catalyst and a $500 \text{ ”m}$ diamond seed crystal.
- Doping Control: The boron concentration gradient (50-3000 ppm) was achieved using mixtures of high-purity graphite and amorphous boron powder (up to 2 wt.% boron for sample D4).
- Sample Preparation: Thin sections (0.185 mm (110) and 0.31 mm (100) orientations) were prepared via laser cutting and subsequent precision polishing.
- Boron Concentration Mapping: The concentration gradient was estimated using Synchrotron X-ray diffraction measurements of lattice parameters and verified via Raman and FTIR spectroscopy along specific paths on the crystal face.
- Hardness Measurement ($H_v$): Vickers hardness was determined using a standard square-pyramidal diamond indenter across loads from 0.1 to 10 N.
- Indentation Imaging Validation (Critical Step): Indentations were analyzed using both Scanning Electron Microscopy (SEM) and, critically, High-resolution 3D Optical Microscopy (Bruker ContourGT). The 3D depth information was essential to accurately distinguish the true indentation edge from surrounding brittle cracks, yielding reliable $H_v$ values in the ultrahard range.
- Elastic Property Measurement: Elastic moduli ($C_{ij}, G_0, K_s$) were constrained using two complementary high-precision techniques:
- Brillouin-Mandelstam spectroscopy (BMS).
- GHz-ultrasonic interferometry, combined with a newly developed optical contact micrometer for high-precision length measurement (accurate to $\pm 1 \text{%}$ uncertainty).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the need for precision-engineered, high-quality Boron-Doped Diamond (BDD) materials for defining physical properties in the ultrahard regime and advancing BDD semiconductor applications. 6CCVD is uniquely positioned to supply the materials required to replicate, confirm, and extend this critical work.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the compositional range and high purity required for this fundamental study, 6CCVD recommends:
- Boron-Doped Single Crystal Diamond (SCD-BDD): We offer custom boron doping from trace levels (for properties equivalent to pure diamond) up to heavy doping (>3000 ppm) necessary to investigate mechanical softening and superconductivity.
- High Purity Polycrystalline Diamond (PCD): While this study focused on single crystal, extension into nano- or micro-polycrystalline BDD (PCD-BDD) for Hall-Petch effect studies requires high-quality PCD starting material, available in inch-size wafers from 6CCVD.
Customization Potential
Section titled âCustomization PotentialâThe success of this research relied on tight control over crystal dimensions, orientation, and surface qualityâall core competencies of 6CCVD:
| Requirement from Paper | 6CCVD Custom Capability | Value Proposition |
|---|---|---|
| Material Form | Single Crystal Diamond (SCD) or Polycrystalline Diamond (PCD) substrates. | Custom plates/wafers up to 125 mm diameter (PCD). |
| Thickness | $0.185 \text{ mm}$ and $0.31 \text{ mm}$ sections used. | SCD and PCD thickness control from $0.1 \text{ ”m}$ to $500 \text{ ”m}$. Substrates up to $10 \text{ mm}$. |
| Crystal Orientation | (110) and (100) orientations studied. | Guaranteed control of crystal growth orientation for SCD plates. |
| Surface Finish | Extreme polishing required for accurate $H_v$ measurements. | Guaranteed surface roughness Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD). |
| Metalization | Future BDD electronic devices often require contacts (e.g., Ti/Au). | Internal capability for custom thin-film metalization: Au, Pt, Pd, Ti, W, Cu layers. |
| Doping Gradient | Study relies on continuous compositional boron gradients. | Capability to deliver BDD materials with highly controlled, uniform, or graded doping profiles to support next-generation semiconductor R&D. |
Engineering Support
Section titled âEngineering SupportâUnderstanding the complex relationship between boron incorporation, crystalline defects, and mechanical softening is crucial for both superabrasive design and optimizing BDD for extreme semiconductor environments.
6CCVDâs in-house PhD engineering team specializes in diamond material physics and can assist clients with material selection and specification development for similar ultrahard materials projects, high-power electronics, and sensor applications requiring tailored BDD characteristics.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Alternative approaches to evaluating the hardness and elastic properties of materials exhibiting physical properties comparable to pure diamond have recently become necessary. The classic linear relationship between shear modulus ( G ) and Vickers hardness ( H V ), along with more recent non-linear formulations based on Pughâs modulus extending into the superhard region ( H V > 40 GPa) have guided synthesis and identification of novel superabrasives. These schemes rely on accurately quantifying H V of diamond-like materials approaching or potentially exceeding the hardness of the diamond indenter, leading to debate about methodology and the very definition of hardness. Elasticity measurements on such materials are equally challenging. Here we used a high-precision, GHz-ultrasonic interferometer in conjunction with a newly developed optical contact micrometer and 3D optical microscopy of indentations to evaluate elasticity-hardness relations in the ultrahard range ( H V > 80 GPa) by examining single-crystal boron-doped diamond (BDD) with boron contents ranging from 50-3000 ppm. We observe a drastic elastic-mechanical softening in highly doped BDD relative to the trends observed for superhard materials, providing insight into elasticity-hardness relations for ultrahard materials.