High-Energy Excimer Annealing of Nanodiamond Layers

At a Glance

Metadata	Details
Publication Date	2023-01-30
Journal	Nanomaterials
Authors	Klaudia Hurtuková, Nikola Slepičková Kasálková, Dominik Fajstavr, Ladislav Lapčák, Václav Švorčı́k
Institutions	University of Chemistry and Technology, Prague
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Energy Excimer Annealing of Nanodiamond Layers

This document analyzes the research on converting nanodiamond (ND) films into Q-carbon via high-energy excimer laser annealing, highlighting 6CCVD’s capabilities to supply the necessary high-purity CVD diamond materials and custom engineering services required for replicating and scaling this advanced carbon research.

Executive Summary

This study successfully demonstrates the conversion of CVD-grown nanodiamond (ND) films into Quenched Carbon (Q-carbon) structures using high-energy excimer laser annealing. This process is critical for developing materials with exceptional properties, such as ultra-hardness and high-temperature superconductivity.

Q-Carbon Synthesis: Nanodiamond films (1000 nm thick) were exposed to a high-energy KrF excimer laser (248 nm, 20-40 ns pulse duration) under high vacuum, inducing rapid melting and quenching.
Morphological Transformation: Increasing laser fluence (up to 3000 mJ cm^-2) destroyed the original ND structure, creating a highly stressed, fibrous structure characteristic of Q-carbon, interspersed with layered micro-/nano-spheres (microdiamonds).
Hybridization Conversion: X-ray photoelectron spectroscopy (XPS) confirmed a significant conversion from the pristine ND state (78% sp² hybridization) to a highly sp³-dominant structure (up to ~80% sp³), essential for Q-carbon formation.
Bonding Confirmation: Raman spectroscopy confirmed the presence of the diamond (sp³) phase (1332 cm^-1 peak) and a low-intensity graphitic (G) peak, consistent with Q-carbon.
Interface Effects: High laser fluences (2000 and 3000 mJ cm^-2) caused partial blasting of the ND film, leading to the formation of Si-C carbide bonds at the film-silicon substrate interface.
Application Potential: This method provides a viable route for synthesizing Q-carbon, a material cited as being up to 40% harder than diamond and possessing extraordinary electronic properties, suitable for next-generation cutting tools and spintronic devices.

Technical Specifications

The following hard data points were extracted from the experimental results and methodology:

Parameter	Value	Unit	Context
Initial ND Film Thickness	1000	nm	CVD-prepared film on Si wafer
Initial ND Grain Size	200-300	nm	Ultrananocrystalline diamond starting material
Excimer Laser Wavelength	248	nm	KrF laser source used for annealing
Laser Pulse Duration	20-40	ns	Required for ultra-fast quenching
Laser Fluence Range Tested	1600 to 3000	mJ cm^-2	Range used to induce phase change
Pristine ND sp² Content	78.4	%	Measured by XPS C 1s spectrum
Highest sp³ Content Achieved	47.6	%	Measured at 1600 mJ cm^-2 (Note: Q-carbon structure is assumed to be ~80% sp³)
Si-C Bond Content (Max)	24.9	%	Measured at 3000 mJ cm^-2, indicating substrate interaction
Diamond Raman Peak Position	1332	cm^-1	Confirmed sp³ diamond phase
Graphitic G Peak Position	1582	cm^-1	Low intensity, indicating minimal graphitization
Diamond XRD Peak Position	44.1	°2θ	Broadening observed with increasing energy
Maximum Oxygen Content (Laser Exposed)	5	wt%	Measured by EDS

Key Methodologies

The conversion of nanodiamond to Q-carbon relied on precise control over the starting material and the high-energy laser parameters:

Starting Material: Ultrananocrystalline diamond (ND) film (1000 nm thick) prepared via Chemical Vapor Deposition (CVD) on a high-purity silicon (Si) wafer substrate.
Annealing Environment: Treatment was conducted in high-vacuum conditions to prevent atmospheric reactions during the high-temperature phase change.
Excimer Laser Treatment: A high-energy pulsed KrF excimer laser (248 nm wavelength) was used to achieve nanosecond-scale melting and ultra-fast cooling (quenching).
Fluence Control: Samples were exposed to single laser shots at controlled fluences: 1600, 2000, and 3000 mJ cm^-2.
Chemical Analysis: X-ray Photoelectron Spectroscopy (XPS) was used to deconvolute the C 1s spectra, quantifying the conversion ratio of sp² to sp³ hybridization and confirming the formation of Si-C carbide bonds.
Structural Confirmation: Raman spectroscopy and X-ray Diffraction (XRD) confirmed the presence of the diamond (sp³) phase (1332 cm^-1) and the broadening of the diamond (111) peak, indicative of the modified Q-carbon structure.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to support and advance research into Q-carbon and other advanced carbon polymorphs by providing high-quality, customizable MPCVD diamond films and expert engineering support.

Applicable Materials for Q-Carbon Research

The successful synthesis of Q-carbon relies on a high-quality, uniform nanodiamond starting layer. 6CCVD provides the ideal precursors:

Material Requirement (Paper)	6CCVD Solution	Technical Advantage
Ultrananocrystalline Diamond Film	Polycrystalline Diamond (PCD)	We offer high-purity MPCVD PCD films with tunable grain sizes and controlled surface morphology, ideal for use as precursor films.
High sp³ Content Precursor	Optical Grade SCD or High-Purity PCD	Our Single Crystal Diamond (SCD) and high-ppurity PCD films ensure minimal non-diamond carbon content, maximizing the efficiency of the sp² to sp³ conversion during laser annealing.
Substrate Compatibility	Custom Substrates (Si, Sapphire, etc.)	We routinely grow diamond films on various substrates, including high-purity Silicon wafers (up to 10 mm thick), ensuring compatibility with existing experimental setups.

Customization Potential for Scaling and Device Integration

The ability to scale Q-carbon synthesis and integrate it into functional devices requires precise control over dimensions, thickness, and interface engineering—all core 6CCVD capabilities.

Custom Dimensions: While the paper used small samples (32 x 13 mm²), 6CCVD can provide inch-size PCD wafers up to 125 mm in diameter, enabling wafer-scale integration and industrial scaling of Q-carbon synthesis for applications like radiation shielding or large-area electronics.
Thickness Control: The paper utilized a 1000 nm (1 µm) film. 6CCVD offers precise thickness control for both SCD and PCD films, ranging from 0.1 µm up to 500 µm, allowing researchers to optimize the film depth for specific laser penetration and quenching dynamics.
Interface Engineering: The formation of Si-C bonds at the interface was noted at high fluences. 6CCVD’s expertise in CVD growth allows for the customization of buffer layers or interface treatments to manage stress, adhesion, and chemical bonding between the diamond film and the substrate, crucial for controlling the resulting Q-carbon structure.
Advanced Metalization: For applications utilizing Q-carbon’s reported superconductivity or field emission properties, 6CCVD offers internal metalization services (Au, Pt, Pd, Ti, W, Cu) for creating ohmic contacts or complex electrode patterns directly onto the diamond or Q-carbon layer.
Ultra-Low Roughness Polishing: For applications requiring exceptional surface quality (e.g., nanoindentation or high-resolution imaging mentioned in the paper), 6CCVD provides ultra-low roughness polishing (Ra < 1 nm for SCD, Ra < 5 nm for inch-size PCD).

Engineering Support

The conversion of ND to Q-carbon involves complex phase transitions driven by extreme thermal gradients. 6CCVD’s in-house PhD team specializes in optimizing MPCVD recipes to achieve specific material properties.

Material Selection Consultation: Our experts can assist researchers in selecting the optimal starting material (e.g., specific grain size PCD vs. ultra-thin SCD) to maximize the yield and purity of the resulting Q-carbon phase.
CVD Recipe Optimization: We offer consultation on modifying CVD parameters to tailor the initial sp²/sp³ ratio of the nanodiamond precursor film, potentially reducing the required laser energy for complete conversion.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).

View Original Abstract

Here, we aimed to achieve exposure of a nanodiamond layer to a high-energy excimer laser. The treatment was realized in high-vacuum conditions. The carbon, in the form of nanodiamonds (NDs), underwent high-temperature changes. The induced changes in carbon form were studied with Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction (XRD) and we searched for the Q-carbon phase in the prepared structure. Surface morphology changes were detected by atomic force microscopy (AFM) and scanning electron microscopy (SEM). NDs were exposed to different laser energy values, from 1600 to 3000 mJ cm−2. Using the AFM and SEM methods, we found that the NDs layer was disrupted with increasing beam energy, to create a fibrous structure resembling Q-carbon fibers. Layered micro-/nano-spheres, representing the role of diamonds, were created at the junction of the fibers. A Q-carbon structure (fibers) consisting of 80% sp3 hybridization was prepared by melting and quenching the nanodiamond film. Higher energy values of the laser beam (2000 and 3000 mJ cm−2), in addition to oxygen bonds, also induced carbide bonds characteristic of Q-carbon. Raman spectroscopy confirmed the presence of a diamond (sp3) phase and a low-intensity graphitic (G) peak occurring in the Q-carbon form samples.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano13030557

References

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2022 - Progress and challenges of graphene and its congeners for biomedical applications [Crossref]
2020 - Formation of Q-carbon by adjusting sp3 content in diamond-like carbon films and laser energy density of pulsed laser annealing [Crossref]
2019 - Diamond film growth by HFCVD on Q-carbon seeded substrate [Crossref]