Mesoscopic physical removal of material using sliding nano-diamond contacts

At a Glance

Metadata	Details
Publication Date	2018-02-08
Journal	Scientific Reports
Authors	Umberto Celano, Feng‐Chun Hsia, Danielle Vanhaeren, Kristof Paredis, Torbjörn E. M. Nordling
Institutions	KU Leuven, IMEC
Citations	38
Analysis	Full AI Review Included

Technical Documentation & Analysis: Mesoscopic Material Removal using Nano-Diamond Contacts

Source Paper: Celano et al., Mesoscopic physical removal of material using sliding nano-diamond contacts, Scientific Reports (2018) 8:2994.

Executive Summary

This research validates the critical role of high-quality, wear-resistant diamond materials in achieving ultra-precise, controlled material removal necessary for advanced nanoscale applications like 3D Atomic Force Microscopy (AFM) tomography.

Controlled Removal Demonstrated: Achieved highly controllable material removal rates (RR) below 5 nm/scan across diverse hard materials (Si, Ge, Pt, TiN, SiO₂), crucial for high-depth resolution 3D characterization.
Diamond Tip Integrity: Boron-Doped Diamond (BDD) tips were utilized as the sliding counterbody, demonstrating superior wear resistance essential for maintaining stable contact geometry during prolonged, high-pressure scanning (up to 10 µN).
Mechanism Modeling: Identified and modeled two distinct contact regimes—low-force sliding (elastic) and high-force ploughing (plastic deformation)—separated by a material-dependent threshold force (F_th, 1-4 µN range).
Surface Quality Optimization: Demonstrated that increasing the scan line density significantly improves the final surface quality of the machined area, achieving roughness (Ra) down to 0.28 nm.
High-Pressure Operation: The material removal process operates effectively when contact pressures reach the range of tens of GPa, leveraging the brittle-to-ductile transition in semiconductors like Silicon.
Application Focus: Provides the fundamental understanding and control parameters required for confined-volume characterization and nano-manufacturing in semiconductor and materials science.

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on the parameters relevant to diamond material performance and nanoscale wear control.

Parameter	Value	Unit	Context
Load Force Range Investigated	1 - 10	µN	Applied force range for material removal experiments.
Controllable Removal Rate (RR)	< 5	nm/scan	Demonstrated control level for 3D AFM tomography applications.
Threshold Force (F_th) Range	1 - 4	µN	Defines transition between elastic sliding and plastic ploughing regimes.
Nominal Tip Radius (r_tip)	15	nm	Pyramidal Solid Diamond Probes (FDT) used as counterbody.
Cantilever Spring Constant	10	N/m	Stiffness of the AFM cantilever used for scanning.
Contact Pressure (High Force)	Tens of	GPa	Pressure reached in the 2-4 µN range, inducing plastic deformation.
Final Surface Roughness (Ra)	0.28	nm	Achieved in the machined area using high line density (512 lines/image).
Wear Coefficient (k) - Low Force	10^-2	N/A	Corresponds to the ductile wear regime (sliding).
Wear Coefficient (k) - High Force	10^-1	N/A	Corresponds to the brittle wear regime (ploughing).
Substrate Materials Tested	Si, SiGe, Ge, Pt, TiN, SiO₂	N/A	Demonstrates diamond tip efficacy across semiconductors, metals, and oxides.

Key Methodologies

The experiments relied on precise control of the diamond tip geometry and scanning parameters to achieve stable, quantifiable material removal.

Tip Material Selection: Used in-house developed Full-Diamond Tips (FDT), specifically Boron-Doped Diamond (BDD), characterized by high resolution TEM (tip apex scale bar 20 nm) to ensure pyramidal shape and high crystallinity.
Experimental Setup: Measurements performed in air using a Digital Instrument Dimension 3100 AFM equipped with a Nanoscope controller.
Scanning Parameters: Constant scan frequency of 0.6 Hz; trenches created by 20 consecutive AFM scans over a fixed area (4 µm x 500 nm).
Load Variation: Load force systematically varied from 1 µN to 10 µN to map the transition between contact regimes.
Removal Rate (RR) Calculation: RR determined by dividing the height difference (depth) inside and outside the trench by the number of scans.
Surface Analysis: Machined areas and tip apex contamination inspected using Tapping Mode AFM and Scanning Electron Microscopy (SEM) (Hitachi SU8000) to assess surface quality and tip integrity.
Modeling: Developed a two-mechanism model combining Archard’s law (sliding) and continuum mechanics contact theory (plastic deformation/indentation) to accurately fit the non-linear RR dependence on load force.

6CCVD Solutions & Capabilities

The research highlights the necessity of ultra-hard, high-quality diamond materials for reproducible nanoscale wear and manufacturing processes. 6CCVD is uniquely positioned to supply the foundational materials and engineering support required to replicate and advance this work.

Applicable Materials

The study utilized Boron-Doped Diamond (BDD) tips for their superior hardness, wear resistance, and conductivity. 6CCVD provides the necessary source material for manufacturing such high-performance probes or for use as wear-resistant substrates:

Boron-Doped Diamond (BDD): 6CCVD offers high-quality BDD material, ideal for fabricating conductive and extremely wear-resistant AFM probes, replicating the FDTs used in this study.
Optical Grade Single Crystal Diamond (SCD): For applications requiring the highest possible purity and lowest surface roughness (Ra < 1 nm), 6CCVD SCD wafers provide an unparalleled platform for studying fundamental tribology and wear mechanisms.
Polycrystalline Diamond (PCD): Available in large formats (up to 125 mm diameter), 6CCVD PCD substrates offer robust, large-area platforms for high-throughput nano-manufacturing and wear testing against various counterbodies.

Customization Potential

The success of this research hinges on precise tip geometry and integration. 6CCVD’s in-house capabilities directly address the need for custom components:

Research Requirement	6CCVD Customization Capability	Value Proposition
Custom Tip Fabrication Material	SCD, PCD, and BDD substrates up to 500 µm thick.	Provides the highest quality MPCVD diamond source material for robust, custom probe manufacturing.
Substrate Dimensions	Plates/wafers up to 125 mm (PCD) and custom SCD sizes. Substrate thickness up to 10 mm.	Supports scaling of experiments from small research coupons to inch-size wafers for industrial testing.
Surface Finish	SCD polishing to Ra < 1 nm; Inch-size PCD polishing to Ra < 5 nm.	Ensures the initial surface quality required for minimizing artifacts and accurately defining the contact area in nanoscale wear studies.
Integration & Metalization	Internal capability for depositing Au, Pt, Pd, Ti, W, Cu.	Allows for custom metal contacts or adhesion layers on diamond substrates, facilitating integration into complex AFM/SPM systems or testing novel metal/diamond interfaces.

Engineering Support

The non-linear relationship between load force and removal rate, coupled with the critical role of scan density in surface quality, necessitates expert material and process consultation.

6CCVD’s in-house PhD team specializes in MPCVD diamond growth, processing, and surface engineering. We offer direct consultation to assist researchers and engineers in:

Material Selection: Optimizing the diamond grade (SCD vs. PCD vs. BDD) and doping level for specific nanoscale wear, friction, or 3D AFM tomography projects.
Process Optimization: Advising on material specifications (e.g., surface orientation, roughness, thickness) to achieve stable, ultra-precise removal rates (< 5 nm/scan) demonstrated in this paper.
Custom Geometry: Providing laser cutting and shaping services for unique diamond components required for advanced SPM setups.

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

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41598-018-21171-w