Experimental Investigation of Laser Parameters Dependence of Surface Graphitization in Nanosecond Laser Ablation of Nanocrystalline Diamond

At a Glance

Metadata	Details
Publication Date	2025-03-26
Journal	Micromachines
Authors	Huixin Yuan, Chunyu Zhang, Chengwei Song, Zhibing He, Li Guo
Institutions	China Academy of Engineering Physics
Citations	2
Analysis	Full AI Review Included

Technical Analysis: Nanosecond Laser Ablation of Nanocrystalline Diamond (NCD)

This document analyzes the research on optimizing nanosecond laser parameters for surface graphitization in Nanocrystalline Diamond (NCD). The findings are leveraged to demonstrate how 6CCVD’s advanced MPCVD diamond materials and customization services can support and extend this research into scalable industrial applications, particularly in microtexturing, tribology, and conductive component development.

Executive Summary

Research Focus: Experimental investigation into the dependence of surface graphitization (sp³ to sp² phase transition) on nanosecond laser ablation parameters in Nanocrystalline Diamond (NCD).
Application Relevance: Controlled graphitization is essential for fabricating high-performance conductive components and enhancing surface properties (e.g., wear resistance, self-lubrication) through microtexturing.
Methodology: Systematic single-factor optimization of laser power, scanning speed, defocus level, and scanning interval using a 532 nm nanosecond pulsed YAG laser.
Key Achievement: Identification of a single-factor optimal parameter set that maximizes the degree of graphitization (highest I_G/I_D ratio) while minimizing surface defects and roughness.
Optimal Parameters: Achieved maximum graphitization at 25 mW Laser Power, 0.1 mm/s Scanning Speed, 0.2 mm Defocus Level, and 6 µm Scanning Interval.
Surface Quality: The optimized process resulted in a smooth, structurally uniform graphitized layer with a minimum surface roughness (Sa) of 744 nm.
6CCVD Value Proposition: 6CCVD provides scalable, high-quality Polycrystalline Diamond (PCD) and intrinsically conductive Boron-Doped Diamond (BDD) substrates, offering superior alternatives for replicating and scaling this laser processing research.

Technical Specifications

The following table summarizes the critical material and process parameters extracted from the experimental investigation.

Parameter	Value	Unit	Context
Sample Material	Nanocrystalline Diamond (NCD)	N/A	Synthesized via HF-CVD
Sample Dimensions	2 x 2 x 1	mm	Workpiece size
Laser Type	Nanosecond Pulse YAG	N/A	Irradiation source
Laser Wavelength	532	nm	Green light
Pulse Duration	5	ns	Fixed parameter
Repetition Rate	1	kHz	Fixed parameter
Optimal Laser Power	25	mW	For maximum graphitization (Range: 15-35 mW)
Optimal Scanning Speed	0.1	mm/s	For uniform graphitization (Range: 0.05-0.25 mm/s)
Optimal Defocus Level	0.2	mm	Maximized deposited layer area (Range: 0-0.4 mm)
Optimal Scanning Interval	6	µm	Highest I_G/I_D ratio (Range: 0-12 µm)
Minimum Surface Roughness (Sa)	744	nm	Achieved at 6 µm interval
Graphitization Metric	I_G/I_D Ratio	N/A	Integrated intensity ratio of G peak (~1580 cm^-1) to D peak (~1350 cm^-1)

Key Methodologies

The experimental investigation relied on precise material synthesis and controlled laser ablation, followed by advanced structural and morphological characterization.

NCD Synthesis: Nanocrystalline Diamond (NCD) samples were fabricated using Hot-Filament Chemical Vapor Deposition (HF-CVD) on diamond-pellet pretreated substrates, following standardized heteroepitaxial protocols.
Laser System Configuration: A nanosecond pulse YAG laser (532 nm, 5 ns, 1 kHz) was used. Laser power was precisely regulated using a Glan prism (1 mW precision).
Ablation Strategy: The process involved two modes: laser linear scanning (1D movement) and laser surface scanning (periodic reciprocating linear scans for 2D coverage).
Parameter Optimization: A single-factor experimental design was used to systematically vary four key parameters:
- Laser Power (15-35 mW, 5 mW interval).
- Scanning Speed (0.05-0.25 mm/s, 0.05 mm/s interval).
- Defocus Level (0-0.4 mm, 0.1 mm interval).
- Scanning Interval (0-12 µm, 2 µm interval).
Morphological Analysis: Scanning Electron Microscopy (SEM) was utilized to observe surface modifications, deposited metamorphic layers, debris, and Laser-Induced Periodic Surface Structures (LIPSS).
Structural Characterization: Raman spectroscopy (532 nm excitation) was the primary tool for quantifying graphitization. The degree of graphitization was determined by calculating the I_G/I_D intensity ratio using Gaussian curve fitting of the D and G peaks.
Surface Quality Assessment: White light interferometry was used to measure the arithmetic mean height deviation (Sa) of the ablated microgrooves, confirming minimum roughness (744 nm) at the optimal scanning interval.

6CCVD Solutions & Capabilities

The research demonstrates the potential of laser processing NCD for advanced applications requiring patterned conductive layers or enhanced tribological surfaces. 6CCVD offers superior MPCVD diamond materials and processing capabilities to accelerate the transition of this research from lab-scale NCD to scalable, high-performance diamond solutions.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Nanocrystalline Diamond (NCD) Substrate	High-Purity Polycrystalline Diamond (PCD)	6CCVD specializes in MPCVD PCD wafers up to 125 mm diameter. Our PCD offers superior scalability, uniformity, and thickness control (0.1 µm to 500 µm) compared to the HF-CVD NCD used in the study.
Conductive Layer Requirement (Graphitization)	Boron-Doped Diamond (BDD) Films	For applications requiring stable, high-performance conductivity (e.g., electrodes, sensors), BDD eliminates the need for post-processing graphitization. We supply BDD in both Single Crystal (SCD) and Polycrystalline (PCD) formats with controlled doping levels.
Precise Microtexturing Substrates	Ultra-Low Roughness Polishing	The study achieved Sa = 744 nm. 6CCVD provides SCD substrates polished to Ra < 1 nm and inch-size PCD polished to Ra < 5 nm, offering an ideal, defect-free starting surface for high-precision laser ablation and microgroove fabrication.
Custom Sample Dimensions (2x2 mm)	Custom Dimensions & Laser Cutting	While the study used small samples, 6CCVD can provide large-area SCD and PCD wafers, along with precision laser cutting services to yield custom shapes and dimensions required for specific R&D or production needs.
Integration of Conductive Features	In-House Metalization Services	For creating robust electrical contacts on graphitized or BDD surfaces, 6CCVD offers internal metalization capabilities, including standard stacks like Ti/Pt/Au, W, Cu, and Pd, ensuring reliable integration into devices.
Optimization Guidance	Expert Engineering Support	6CCVD’s in-house PhD team can assist researchers and engineers with material selection, optimizing diamond properties (e.g., grain size, doping level) to complement specific laser processing recipes for similar microtexturing and tribology projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures rapid delivery of your custom diamond solutions.

View Original Abstract

Nanocrystalline diamond (NCD) is regarded as a highly promising composite engineering material owing to its superior mechanical properties. Surface texturing significantly enhances the surface performance of NCD. Given the unique inherent combination of hardness and brittleness in NCD, laser ablation emerges as a critical method for fabricating surface microstructures. However, the research on laser-induced surface texturing of NCD remains limited. This study experimentally investigated the characteristics of nanosecond laser-ablation-induced graphitization in NCD and provided an in-depth analysis of the laser ablation mechanism, aiming to guide the optimization of NCD surface microtexture manufacturing. Specifically, we conducted systematic nanosecond pulse laser ablation experiments on NCD samples and utilized Raman spectroscopy to qualitatively characterize the graphitization within microgrooves and across the entire ablated surface. The effects of the laser scanning speed, power, defocus level, and scanning interval on the graphitization extent and morphological characteristics were systematically investigated, identifying the single-factor optimal parameter set for maximizing graphitization. Through single-factor experimental analysis, the findings of this study provide foundational data for subsequent multivariate-coupled optimization and offer theoretical support for enhancing the surface properties of NCD through microtexturing via laser ablation.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi16040374

References

2024 - Microstructure Control and Mechanical Properties of Ultra-Nanocrystalline Diamond Films [Crossref]
2024 - Investigation on Nanocrystalline Diamond Film with High Hardness [Crossref]
2020 - Shock Response of Full Density Nanopolycrystalline Diamond [Crossref]
2021 - Femtosecond Laser Micromachining of Diamond: Current Research Status, Applications and Challenges [Crossref]
2024 - A Review of Diamond Synthesis, Modification Technology, and Cutting Tool Application in Ultra-Precision Machining [Crossref]
2004 - Growth of Nanocrystalline Diamond Films on Co-Cemented Tungsten Carbide Substrates by Hot Filament CVD [Crossref]
2021 - Behaviors of Carbon Atoms Induced by Friction in Mechanical Polishing of Diamond [Crossref]
2022 - Experimental Study on the Effect of Surface Texture on Tribological Properties of Nanodiamond Films under Water Lubrication [Crossref]
2020 - Designing Ultrahard Nanostructured Diamond through Internal Defects and Interface Engineering at Different Length Scales [Crossref]