Laser Irradiation Responses of a Single-Crystal Diamond Produced by Different Crystal Growth Methods
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-08-09 |
| Journal | Applied Sciences |
| Authors | Nozomi Takayama, Jiwang Yan |
| Institutions | Keio University |
| Citations | 21 |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Advanced Laser Micro-Machining of Single-Crystal Diamond
Section titled âTechnical Analysis & Documentation: Advanced Laser Micro-Machining of Single-Crystal DiamondâResearch Paper: Laser Irradiation Responses of a Single-Crystal Diamond Produced by Different Crystal Growth Methods Authors: Nozomi Takayama and Jiwang Yan Source: Applied Sciences (2017)
Executive Summary
Section titled âExecutive SummaryâThis study establishes critical laser processing criteria by comparing the nanosecond pulsed Nd:YAG irradiation responses of high-purity HPHT Single Crystal Diamond (SCD) versus MPCVD SCD.
- Process Criteria Established: Significant differences in laser-induced surface features and damage thresholds were found between HPHT and CVD diamond, dictated primarily by crystal defect density and optical properties (transmission/refractive index).
- Reverse Irradiation Discovery (HPHT): At lower fluences (below 10.3 J/cm2), HPHT diamond only machined the lower surface due to constructive interference, achieving highly efficient ablation.
- High Aspect Ratio Grooves: The reverse irradiation method produced exceptionally deep, narrow grooves (up to ~50 ”m depth) with rough bottoms, attributed to material removal dominated by spalling rather than graphitization.
- CVD Defect Influence: CVD diamond, exhibiting higher crystal defect density (indicated by the 1424 cm-1 Raman peak), displayed a lower overall ablation threshold and dominant machining on the upper (incident) surface, even when destructive interference occurred.
- Interference Mechanics: The phenomenon confirms that precise laser machining of diamond is highly dependent on optical interference (constructive vs. destructive) mechanisms driven by the materialâs high refractive index (calculated nm = 2.13 for HPHT).
- Debris Control: Reverse irradiation results in significantly cleaner machining, with minimal sp2 (graphite) debris cloud formation observed on the lower machined surface, contrasting sharply with heavy debris on forward-irradiated surfaces.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard parameters and material properties were extracted from the experimental data:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Laser Wavelength | 532 | nm | Nd:YAG, Second Harmonic Generation |
| Pulse Width | 15.6 | ns | Nanosecond Pulse |
| Repetition Frequency | 1 | kHz | Pulse Frequency |
| HPHT Transmission Rate (t) | 75.7 | % | Through 1.1 mm thick sample |
| CVD Transmission Rate (t) | 83.9 | % | Through 1.1 mm thick sample |
| HPHT Refractive Index (nm) | 2.13 | N/A | Calculated value (air n0 = 1) |
| HPHT Upper Surface Threshold (Pupper) | 9.0 | J/cm2 | Effective threshold (Destructive Interference) |
| HPHT Lower Surface Threshold (Plower) | 7.6 | J/cm2 | Effective threshold (Constructive Interference) |
| Machining Fluence Range | 7.8 to 11.0 | J/cm2 | Range tested for groove formation |
| Maximum Groove Depth (HPHT) | ~50 | ”m | Achieved via low-power reverse irradiation |
| HPHT Surface Roughness (Ra) | 0.4 ± 0.1 | nm | High-quality polished surface |
| CVD Surface Roughness (Ra) | 1.8 ± 0.6 | nm | Polished surface |
| CVD Crystal Defect Peak | 1424 | cm-1 | Raman spectroscopy indicator of defects/impurities |
| Graphite Debris Peak | 1561 | cm-1 | Raman peak confirming sp2 bonding in debris |
Key Methodologies
Section titled âKey MethodologiesâThe experimental setup utilized precise control of nanosecond laser pulses to achieve selective diamond ablation.
- Laser Source & Optics: A nanosecond pulsed Nd:YAG laser (532 nm, 15.6 ns, 1 kHz, >1 W power) was used. The beam had an approximate Gaussian distribution and a spot diameter of 85 ”m.
- Beam Control: A galvanometer scanner system (Miramo controller GMP-507005) controlled the laser motion programs.
- Sample Preparation: Rectangular SCD plates (4 x 3.5 x 1.10 mm for CVD; 3 x 3 x 1.10 mm for HPHT) were used, both featuring polished (100) Miller surfaces.
- Sample Mounting: The diamond sample was placed on a base with an opening, ensuring the lower surface was not in contact with the stage, crucial for enabling reverse irradiation analysis.
- Irradiation Process: Samples were scanned at 1 mm/s across a fluence range of 7.8 J/cm2 to 11.0 J/cm2.
- Post-Processing & Cleaning: Samples were chemically cleaned (nitric, sulfuric, perchloric acid solution, heated to ~200 °C) to remove laser-induced debris and residue.
- Analysis: Raman spectroscopy (NRS-3100) analyzed phase transformation (sp2 graphite detection, crystal defect presence). SEM (Inspect S50) and laser probe (MP-3) measured groove morphology and depth.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the critical importance of diamond material quality (defect density and optical transparency) in determining optimal laser micro-machining parameters. 6CCVD offers the specialized materials and engineering support required to replicate and advance this highly precise processing technique.
Applicable Materials for Optimal Laser Processing
Section titled âApplicable Materials for Optimal Laser ProcessingâThe primary differentiator in this study is the crystal growth method (HPHT vs. CVD), directly impacting defect density, transmission, and machinability thresholds. 6CCVDâs MPCVD manufacturing provides complete control over these variables.
| Research Requirement | 6CCVD Material Recommendation | Technical Justification & Advantage |
|---|---|---|
| High Purity/Transparency (For Reverse Irradiation / Constructive Interference) | Optical Grade SCD | Analogous to the high-quality HPHT sample. Ensures maximum transparency and minimal absorption at 532 nm, maximizing constructive interference effects for high-aspect-ratio reverse machining (Plower = 7.6 J/cm2). |
| Controlled Defects/Lower Threshold (For Standard Forward Ablation) | Standard Electronic Grade SCD | Matches the higher defect density found in the studyâs CVD sample (1424 cm-1 peak). This lower quality/higher absorption material facilitates forward ablation and graphitization at lower fluences, enabling easier (though rougher) machining. |
| Thermal/Mechanical Channel Fabrication | PCD Wafers (125 mm) | For large-scale integration into cutting tools or heat spreaders (as mentioned in the Introduction [1,2]). 6CCVD supplies inch-size PCD with ultra-low roughness (Ra < 5 nm) for smooth, high-throughput micro-channel fabrication. |
Customization Potential
Section titled âCustomization PotentialâThe experimental setup utilized 1.1 mm thick SCD plates. 6CCVD excels in providing custom dimensions critical for advanced manufacturing processes.
- Custom Dimensions and Substrates: 6CCVD can supply SCD wafers up to 125 mm (PCD) and custom substrate thicknesses up to 10 mm, significantly exceeding the 1.1 mm samples used in this study, allowing for scaling up micro-channel fabrication.
- Precision Polishing: To achieve the smooth surfaces required for reliable optical interference (HPHT Ra = 0.4 nm), 6CCVD offers world-class polishing services:
- SCD Polishing: Ra < 1 nm.
- Inch-size PCD Polishing: Ra < 5 nm.
- Metalization Services: While not central to this ablation study, many downstream applications (e.g., integrating sensors or creating electrodes) require metal contacts. 6CCVD offers in-house metalization with thin films of Au, Pt, Pd, Ti, W, and Cu, providing turn-key solutions for micro-device fabrication.
Engineering Support
Section titled âEngineering SupportâThis research demonstrates that the precise optimization of laser machining is inseparable from material characteristics.
- 6CCVDâs in-house PhD engineering team can assist clients in selecting the appropriate Single Crystal (SCD) or Polycrystalline (PCD) material recipe required to match specific laser ablation parameters (e.g., targeting the low-threshold, defect-driven response of the CVD type, or the high-purity, optically driven response of the HPHT type).
- We offer technical consultation to adapt the âreverse-side irradiationâ technique for creating high-aspect-ratio micro-channels and complex internal structures in customized diamond substrates, optimizing both processing speed and groove quality (depth, width, roughness).
- Global Supply Chain: Materials are shipped globally, DDU default with DDP available, ensuring efficient delivery for international research and production teams.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Responses of two types of single-crystal diamonds, prepared by chemical vapour deposition (CVD) and high pressure high temperature synthesis (HPHT) methods, respectively, to a nanosecond pulsed neodymium-doped yttrium aluminium garnet (Nd:YAG) laser were investigated and compared. It was found that due to the difference in the transmission rate and refractive index, the laser-induced surface/subsurface features of the two types of samples were distinctly different. For the CVD sample, destructive interference takes place on the upper surface, leading to direct ablation of smooth grooves with deposition of graphite. For the HPHT sample, however, laser-induced grooves were formed on the reverse side of the irradiation surface (namely, the lower surface) at certain laser fluences due to the constructive interference phenomenon of the laser and the high refractive index of the material. The reverse-side irradiation resulted in the formation of deep and sharp grooves with rough bottoms and insignificant deposition of graphite on the area surrounding the groove. The machining thresholds for the upper and lower surfaces of both types of diamonds were experimentally obtained and theoretically verified. The findings of this study provide important process criteria for laser machining of different kinds of diamonds. The reverse-side irradiation method enables efficient machining of deep grooves in diamonds using a lower power laser.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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