Low-Power Laser Graphitization of High Pressure—High Temperature Nanodiamond Films

At a Glance

Metadata	Details
Publication Date	2020-05-11
Journal	Applied Sciences
Authors	Konstantin G. Mikheev, T. N. Mogileva, Arseniy E. Fateev, Nicholas Nunn, Olga Shenderova
Institutions	North Carolina State University, Udmurt Federal Research Center, Ural Branch of the Russian Academy of Sciences
Citations	14
Analysis	Full AI Review Included

Technical Analysis: Low-Power Laser Graphitization of HP-HT Nanodiamond Films

This document analyzes the research paper “Low-Power Laser Graphitization of High Pressure—High Temperature Nanodiamond Films” to provide technical documentation and identify specific material solutions available through 6CCVD.

Executive Summary

Core Achievement: Demonstrated low-power, continuous-wave (CW) laser-induced graphitization (sp³ to sp² carbon transformation) in 150 nm HP-HT nanodiamond films.
Methodology: Focused 633 nm He-Ne laser irradiation was applied to 20 µm thick nanodiamond films deposited on quartz substrates, requiring relative motion between the beam and the film.
Critical Threshold: Graphitization initiates when the laser intensity exceeds a threshold of approximately 33 kW/cm².
Mechanism Confirmation: The transformation is accompanied by green up-conversion luminescence, confirming a two-step sequential resonance absorption mechanism involving the ionization of Ni- and [Ni-N]-impurity centers.
Structural Change: Laser exposure creates micro-scale features, including a notch (150 nm deep) flanked by parallel ridges (100 nm high), confirming localized material modification.
Commercial Implication: The findings suggest a novel, low-power method for laser-assisted purification of HP-HT nanodiamonds by selectively destroying luminescent nickel-containing centers.

Technical Specifications

The following hard data points were extracted from the research paper:

Parameter	Value	Unit	Context
Nanodiamond Synthesis Method	HP-HT	N/A	High-Pressure High-Temperature synthesis.
Nanodiamond Particle Size (Average)	150	nm	Used for thin film preparation.
Film Thickness (Primary Study)	20	µm	Used for laser modification experiments.
Film Thickness (Extinction Study)	0.5	µm	Used to measure extinction spectrum maximum.
Substrate Material	Quartz	N/A	Used for film deposition.
Excitation Laser Wavelength	633	nm	CW He-Ne laser used for graphitization.
Graphitization Threshold Intensity	33	kW/cm²	Minimum intensity required for sp³ to sp² transformation.
Maximum Laser Intensity Used	65	kW/cm²	Used with 100x objective (8.4 mW output).
Laser Beam Waist Diameter (100x)	4.1	µm	Diameter at the focal plane.
Blackened Line Width (Transverse)	5	µm	Width of laser-written features.
Diamond Raman Shift (Non-Blackened)	1331	cm^-1	Characteristic sp³ peak frequency shift.
Graphitized Raman Shifts (Blackened)	1320, 1580	cm^-1	Broad peaks typical for sp²-carbon.
AFM Notch Depth (Blackened Area)	150	nm	Depth of the laser-induced notch.
AFM Ridge Height (Blackened Area)	100	nm	Height of parallel formations flanking the notch.

Key Methodologies

The experimental procedure focused on thin film preparation, precise laser irradiation, and comprehensive structural analysis:

Material Sourcing and Dispersion: HP-HT nanodiamond particles (150 nm) were sourced and dispersed in deionized water to form an aqueous suspension.
Film Fabrication: Thin films (20 µm and 0.5 µm) were created by drop-casting the nanodiamond suspension onto quartz substrates and drying at room temperature.
Structural Characterization (Pre-Irradiation): Films were analyzed using X-ray Diffraction (XRD) to confirm high-quality diamond structure (peaks at 43.9°, 75.3°, 91.5° for {111}, {220}, {311} planes). Morphology was confirmed via Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).
Laser Setup: A Horiba HR800 Raman spectrometer with a 633 nm He-Ne excitation source was used. Interchangeable objectives (10x, 50x, 100x) provided focused beam diameters down to 4.1 µm.
Laser Modification: The 20 µm film was moved relative to the focused laser beam waist using a coordinate table, scanning the entire surface area.
Graphitization Observation: Blackening (sp³ to sp² conversion) was observed visually and confirmed by the presence of broad Raman lines at 1320 cm^-1 and 1580 cm^-1 in the exposed areas.
Luminescence Analysis: Green up-conversion luminescence (peaks at 485 nm and 528 nm) was recorded during the graphitization process, linking the transformation to the ionization of Ni-related impurity centers.

6CCVD Solutions & Capabilities

6CCVD provides the high-purity, custom-dimensioned MPCVD diamond materials necessary to replicate, control, and scale the laser modification and purification processes demonstrated in this research.

Applicable Materials and Customization Potential

Research Requirement/Application	6CCVD Material Recommendation	Customization & Technical Advantage
High Purity/Defect Control	Optical Grade Single Crystal Diamond (SCD)	Our SCD offers superior purity, enabling precise control over intentionally introduced defects (e.g., N-V centers) without interference from Ni-related complexes common in HP-HT material. Ra < 1 nm polishing ensures optimal laser coupling.
Thin Film Thickness Control	Custom SCD and PCD Films	We offer SCD and PCD layers from 0.1 µm up to 500 µm thick. This allows researchers to precisely control the active volume depth (as noted in the paper) for optimized laser-material interaction.
Scaling and Large Area Processing	Polycrystalline Diamond (PCD) Wafers	We provide PCD plates and wafers up to 125 mm in diameter, suitable for scaling micro-structuring or purification techniques to industrial levels. PCD can be polished to Ra < 5 nm for inch-size wafers.
Conductivity and Charge Mitigation	Heavy Boron-Doped Diamond (BDD)	If the goal is to study the effect of conductivity (similar to the sp² formation observed), BDD films offer controlled metallic or semiconducting properties, eliminating the insulating effects noted in the paper.
Micro-Structure Fabrication	Precision Laser Cutting and Metalization	We offer in-house laser cutting services to define complex patterns and micro-structures (e.g., lines, squares, triangles) with high accuracy. We also provide custom metalization (Au, Pt, Pd, Ti, W, Cu) for integrated optical or electrical contacts.
Substrate Requirements	Custom Substrates (up to 10 mm)	While the paper used quartz, 6CCVD can provide thick diamond substrates (up to 10 mm) for high-power or thermal management applications.

Engineering Support

6CCVD’s in-house team of PhD material scientists specializes in optimizing MPCVD growth parameters to meet demanding research specifications. We can assist engineers and scientists with material selection for similar Laser-Induced Graphitization and Nanodiamond Purification projects, ensuring the starting material properties (purity, doping, thickness) are perfectly matched to the required laser parameters (wavelength, intensity, pulse duration).

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

View Original Abstract

Laser-induced graphitization of 100 nm monocrystals of diamond particles synthesized by high-pressure high-temperature (HP-HT) methods is not typically observed. The current study demonstrates the graphitization of 150 nm HP-HT nanodiamond particles in ca. 20-μm-thick thin films formed on a glass substrate when the intensity of a focused 633 nm He-Ne laser exceeds a threshold of ~ 33 kW/cm2. Graphitization is accompanied by green luminescence. The structure and morphology of the samples were investigated before and after laser excitation while using X-ray diffraction (XRD), Raman spectroscopy, atomic force (AFM), and scanning electron microscopy (SEM). These observations are explained by photoionization of [Ni-N]- and [N]-centers, leading to the excitation of electrons to the conduction band of the HP-HT nanodiamond films and an increase of the local temperature of the sample, causing the transformation of sp3 HP-HT nanodiamonds to sp2-carbon.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app10093329

References

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