The Investigation of Graphene Oxide-Enhanced Hybrid Slurry Preparation and Its Polishing Characteristic on CVD Single Crystal Diamond

At a Glance

Metadata	Details
Publication Date	2024-12-11
Journal	Materials
Authors	Zixuan Wang, Yang Zhao, Jie Yao, Tianbiao Yu, Sheng Qu
Institutions	Northeastern University, Shenyang University of Technology
Citations	2
Analysis	Full AI Review Included

Technical Analysis and Documentation: Graphene Oxide-Enhanced Polishing of CVD Single Crystal Diamond

Executive Summary

This technical analysis focuses on optimizing the Chemical Mechanical Polishing (CMP) of CVD Single Crystal Diamond (SCD) using a novel Graphene Oxide (GO)-enhanced hybrid slurry. The research successfully identified optimal parameters for achieving superior surface quality and high material removal rates (MRR), directly supporting high-precision diamond applications.

Core Achievement: Successful preparation and stabilization of a GO-enhanced hybrid slurry for SCD CMP, leveraging GO’s lubricating and chemical activation properties.
Surface Quality Optimization: Minimum surface roughness (Ra) of 2.36 nm was achieved using Silicon Carbide (SiC) abrasive grains, significantly reducing initial surface defects.
Material Removal Rate (MRR) Optimization: The highest MRR of 1.529 µm/h was achieved at an optimal polishing rotation speed of 4000 rpm.
Optimal Recipe Balance: Diamond abrasive grains with a size of 2.5 µm were identified as providing the best balance between high MRR (1.4x higher than 0.5 µm grains) and improved surface quality.
Tribological Enhancement: The addition of GO slurry reduced the friction coefficient by up to 42% compared to dry friction conditions, facilitating the removal of surface micro-protrusions.
Application Relevance: The findings are critical for engineers requiring ultra-smooth, defect-free SCD surfaces for high-end optical, electronic, and mechanical applications.

Technical Specifications

The following table summarizes the key material properties and optimized experimental results extracted from the research.

Parameter	Value	Unit	Context
Workpiece Material	SCD (100)	N/A	CVD Single Crystal Diamond
Workpiece Dimensions	3 x 3 x 1	mm	Standard sample size used in experiments
Initial Surface Roughness (Ra)	4.1 - 5.1	nm	Range before polishing
Minimum Achieved Ra	2.36	nm	Achieved using SiC abrasive grains
Optimal Diamond Grain Size	2.5	µm	Selected for optimal Ra/MRR balance
Optimal Polishing Speed	4000	rpm	Yielded minimum Ra (3.32 nm) and high MRR
Maximum MRR (Optimal Speed)	1.529	µm/h	Achieved at 4000 rpm
Highest MRR (Abrasive Type)	0.754	µm/h	Achieved using 2.5 µm Diamond abrasive
GO Slurry Concentration	0.1	wt%	Mass percentage used in hybrid slurry
Friction Coefficient Reduction	42	%	Reduction compared to dry friction (at 200 mm/min)
Diamond Hardness (HV)	8300-12,000	HV	Material property of CVD SCD
Diamond Thermal Conductivity	1100	W/m K	Material property of CVD SCD

Key Methodologies

The research employed a rigorous CMP process combined with advanced metrology to quantify material removal and surface quality.

Slurry Preparation:
- Graphene Oxide (GO) aqueous solution (0.49 wt%) prepared via magnetic stirring and ultrasonic dispersion.
- Temperature strictly controlled at 30 °C to prevent GO reduction (< 38 °C).
- GO-enhanced hybrid slurry (0.1 wt% GO, 2.5 µm diamond) prepared using repeated stirring (500 rpm) and ultrasonic dispersion cycles for stability.
Polishing Setup:
- Experiments conducted on a five-axis CNC polishing machine.
- Diamond workpieces fixed with epoxy resin on a polishing head.
- Glass polishing discs used as the fixture.
Material Removal Rate (MRR) Measurement:
- MRR calculated using the contour measurement method: MRR = $\delta$/t (where $\delta$ is the depth difference and t is time).
- Grooves (40 µm depth, 140 µm width, 1 mm length) were machined into the SCD surface using a femtosecond laser prior to polishing.
- Depth difference measured using a 3D measuring laser microscope (OLYMPUS LEXT OLS4100).
Parameter Variation:
- Abrasive Type: Diamond (Mohs 10), SiC (Mohs 9.2-9.6), Al₂O₃ (Mohs 9), and CeO₂ (Mohs 7) were tested.
- Grain Size: Diamond grains tested at 0.5 µm, 2.5 µm, 5 µm, and 9 µm.
- Rotation Speed: Polishing speeds tested at 2000, 3000, 4000, and 5000 rpm (constant pressure 30 N, duration 70 min).
Tribological Testing:
- Single crystal diamond scratching experiments performed on a Multi-functional Material Surface Property Tester (MFT-4000).
- Contact mode: Point-face (Ball diameter 3-6 mm).
- Load: 15 N. Reciprocation speeds: 100, 150, 200 mm/min (with and without GO slurry).

6CCVD Solutions & Capabilities

This research demonstrates the critical need for high-quality, defect-free CVD Single Crystal Diamond (SCD) substrates capable of withstanding rigorous CMP processes while achieving sub-nanometer surface finishes. 6CCVD is uniquely positioned to supply the foundational materials and advanced processing required to replicate and extend this high-precision research.

Applicable Materials

To replicate or extend this research, the highest quality SCD material is required, specifically the (100) orientation used in the study.

Optical Grade SCD (Single Crystal Diamond): 6CCVD provides high-purity, low-defect SCD plates, ideal for CMP studies targeting optical or electronic applications. Our standard SCD is available in thicknesses from 0.1 µm to 500 µm.
Custom Substrates: We can supply SCD workpieces in the exact dimensions used in the study (e.g., 3 mm x 3 mm x 1 mm) or in larger formats, including plates up to 125 mm (PCD) for scaling up research.

Customization Potential

6CCVD’s in-house fabrication capabilities directly address the specialized needs demonstrated by the experimental methodology.

Research Requirement	6CCVD Capability & Advantage
High-Quality Polishing Target	The paper achieved Ra 2.36 nm. 6CCVD guarantees Ra < 1 nm for SCD substrates, providing a superior starting material or final product finish, eliminating the need for extensive post-processing CMP.
MRR Measurement Grooves	The study used femtosecond laser etching to create reference grooves. 6CCVD offers precision laser cutting and micro-machining services to pre-pattern substrates, saving researchers valuable time and equipment access.
Future Electronic Integration	If the polished SCD is intended for electronic devices (e.g., photodetectors, high-power electronics), 6CCVD offers custom metalization (Au, Pt, Pd, Ti, W, Cu) directly onto the polished diamond surface.
Large-Area Polishing	While the study focused on small samples, 6CCVD can polish inch-size Polycrystalline Diamond (PCD) wafers to Ra < 5 nm, enabling the scaling of this GO-enhanced CMP technique to industrial dimensions.

Engineering Support

The optimization of CMP parameters (abrasive type, grain size, rotation speed) requires deep material science expertise. 6CCVD’s in-house PhD team specializes in diamond surface engineering and tribology.

Material Selection Consultation: Our experts can assist researchers in selecting the optimal diamond grade (e.g., SCD vs. PCD) and crystal orientation for specific CMP or tribological projects, ensuring compatibility with novel slurries like GO-enhanced systems.
Process Integration: We offer support in defining the ideal starting surface roughness and thickness (SCD thickness up to 500 µm, substrates up to 10 mm) to maximize efficiency in similar Chemical Mechanical Polishing projects.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond materials directly to your lab.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

As an environment-friendly material, graphene oxide nanosheet can effectively improve the polishing surface quality of single crystal diamond workpieces. However, the lubricating and chemical effects of graphene oxide nanosheets have an uncertain impact on the polishing material removal rate. In this paper, the graphene oxide-enhanced hybrid slurry was prepared with good stability. The femtosecond laser etching and contour measurement method was adopted to analyze the polishing material removal rate of the CVD single crystal diamond workpiece. The surface damage of the workpiece polished with SiC abrasive grains is minimal, while the workpiece with diamond abrasive grains has the largest material removal rate. With an increase in abrasive grain size, the polishing material removal rate increases, but new surface scratches and pits can be introduced if the grain size is too large. Therefore, a grain size of 2.5 μm was selected to improve the surface quality. The surface roughness first decreases and then increases with the increase in polishing rotation speed. At a speed of 4000 rpm, the surface roughness reached its minimum with a relatively high material removal rate simultaneously. A series of CVD single crystal diamond scratching experiments were conducted with different scratching speeds, which proved that graphene oxide can help facilitate material surface micro-protrusion removal.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17246053

References

2024 - Molecular dynamics simulation and experimental study of the material machinability characteristics and crack propagation mechanisms for fused silica double nanoscratches [Crossref]
2024 - A new end edge repairing method for flat end mills on a four-axis machine tool using an irregular grinding wheel [Crossref]
2023 - Enhanced machinability of aluminium-based silicon carbide by non-resonant vibration-assisted magnetorheological finishing
2019 - Fabrication and performance of CVD diamond cutting tool in micro milling of oxygen-free copper [Crossref]
2017 - An investigation on dielectric properties of diamond films in the range of K and Ka band [Crossref]
2019 - Mechanical property enhancement of cubic boron nitride composites through additive diamond [Crossref]
2024 - Honey-Derived Hydrochar Containing 2,2,6,6-tetramethylpiperidine-1-oxyl Free Radical for Degradation of Aqueous Organic Pollutants [Crossref]
2021 - Nanostructured diamond for biomedical applications [Crossref]