Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition

At a Glance

Metadata	Details
Publication Date	2016-01-25
Journal	Scientific Reports
Authors	Hualin Zhan, David J. Garrett, Nicholas V. Apollo, Kumaravelu Ganesan, Desmond W. M. Lau
Institutions	Czech Academy of Sciences, Institute of Physics, RMIT University
Citations	38
Analysis	Full AI Review Included

6CCVD Technical Documentation: High-Performance 3D Graphene Fabrication via PECVD

Executive Summary

This documentation analyzes the successful catalyst-free fabrication of high-surface-area 3D graphene on nanoporous anodic alumina (G-AAO) using a Plasma-Enhanced Chemical Vapor Deposition (PECVD) approach. The resultant material demonstrates exceptional stability and high electrochemical performance, making it a viable candidate for next-generation supercapacitors and biosensors.

Core Achievement: Direct, catalyst-free growth of defected few-layer graphene (FLG) conformally coated on nanoporous dielectric substrates (AAO).
Methodology: A one-step PECVD process utilized a 0.35 mm quartz spacer to achieve high substrate temperatures (up to ~1500 °C) via optimized thermal isolation and plasma-enhanced graphitization.
Material Quality: Raman spectroscopy and EELS confirmed high sp² content (77.2%), indicating better quality graphitization compared to two-step thermal annealing methods.
Electrochemical Performance: A 10 mm³ G-AAO sample achieved a large overall capacitance of 2117 µF (2.1 mF) and a high effective surface area of 882.98 cm².
Stability: G-AAO demonstrated excellent chemical stability, surviving 22 hours in 40% hydrofluoric acid (HF) etching solution, confirming full protective graphene coverage.
6CCVD Relevance: This work highlights advanced MPCVD processing requirements, which are directly analogous to the high-purity, high-temperature growth expertise employed by 6CCVD in fabricating customized single-crystal (SCD) and polycrystalline (PCD) diamond materials.

Technical Specifications

Parameter	Value	Unit	Context
Graphene Growth Temperature (Method 1)	~1500	°C	Achieved via 0.35 mm quartz spacer
PECVD Microwave Power	1.7	kW	PECVD system setting
Reactor Pressure	85	Torr	Growth environment
Gas Flow Ratio (H₂ / CH₄)	750 / 10	sccm	Highly hydrogen-rich plasma
Substrate Type	AAO	N/A	Nanoporous Anodic Aluminum Oxide
AAO Pore Diameter / Thickness	55 / 100	nm / µm	Template geometry
Sheet Resistance (Horizontal)	6.8	kΩ/	G-AAO (Method 1) conductivity
Vertical Resistance (Pore)	5.5	Ω	Confirms conformal graphene coating
Specific Capacitance	2.4	µF/cm²	Measured in 1 mM Fe(CN)₆⁴⁻
Effective Surface Area (10 mm³ sample)	882.98	cm²	Derived from total capacitance
Overall Capacitance (10 mm³ sample)	2117 (2.1)	µF (mF)	High-performance supercapacitor result
Graphene Grain Size (L_a)	~3.3	nm	Estimated from I(D)/I(G) ratio (1.5)
Graphene Sp² Fraction (EELS)	77.2	%	Confirmed graphitization

Key Methodologies

The successful fabrication (Method 1) relied on precisely controlled MPCVD conditions coupled with strategic thermal isolation:

Substrate Preparation: Nanoporous Anodic Aluminum Oxide (AAO) membranes (55 nm pore diameter, 100 µm thickness) were used as the dielectric substrate.
Thermal Isolation Setup: A 0.35 mm thick quartz spacer was intentionally placed between the AAO sample and the molybdenum growth stage to provide electrical and thermal isolation.
PECVD Operation: The sample was placed into the growth chamber under 85 Torr pressure, utilizing a plasma fed by H₂ (750 sccm) and CH₄ (10 sccm) at 1.7 kW microwave power.
High-Temperature Graphitization: The thermal isolation afforded by the spacer allowed the sample temperature to reach approximately 1500 °C, enabling plasma-enhanced conversion of the initial amorphous carbon layer into few-layer graphene (FLG).
Mechanism Confirmation: The dielectric spacer was found crucial for stabilizing the plasma sheath potential, leading to continuous ion bombardment, stable surface charging, and highly repeatable, high-quality graphitization.

6CCVD Solutions & Capabilities

6CCVD provides the high-performance material platforms and customization expertise necessary to replicate or advance this research, particularly in high-stability electrochemical and sensor applications where superior conductivity and chemical robustness are paramount.

Applicable Materials: Boron-Doped Diamond (BDD)

While the paper utilized G-AAO, the requirements for a chemically inert, highly conductive, and high-surface-area electrode platform align perfectly with 6CCVD’s advanced Boron-Doped Diamond (BDD) capabilities. BDD is the gold standard for robust electrochemical sensing and energy storage under extreme conditions.

Heavy Boron-Doped Polycrystalline Diamond (PCD): Ideal for maximizing surface area efficiency in electrochemical systems, offering chemical stability far exceeding that of graphene or amorphous carbon, even in aggressive environments (e.g., HF).
- 6CCVD Capability: PCD wafers available up to 125 mm diameter, allowing for large-scale electrode fabrication.
Boron-Doped Single Crystal Diamond (SCD): Recommended for applications requiring extreme signal purity, low background noise, and ultra-smooth surfaces (Ra < 1 nm), crucial for high-precision biosensors or quantum capacitance studies similar to those performed in the paper.
- 6CCVD Capability: SCD thicknesses available from 0.1 µm to 500 µm.

Customization Potential for Research Replication

To support research requiring unique geometries or integrated contacts, 6CCVD offers complete material customization:

Requirement (Paper Analogy)	6CCVD Customization Service	Benefit to Client
Sample Dimensions (e.g., 3 mm x 3 mm x 0.1 mm)	Custom wafer cutting and shaping (plates/wafers up to 125 mm)	Provides precise geometries for integration into micro-electrochemical cells or specialized PECVD chambers.
High Substrate Processing (1500 °C)	In-house MPCVD/PECVD expertise (high-temperature growth)	Ensures that 6CCVD substrates can withstand the extreme thermal demands necessary for subsequent high-temperature deposition or annealing steps required in this type of material synthesis.
Electrode Contacts (Au blocks)	Custom Metalization Services (Ti/Pt/Au, Au, Pt, Cu, W)	Enables the fabrication of pre-metalized BDD electrodes for immediate use as working electrodes (WE) or counter electrodes (CE) in three-electrode electrochemical cells.
Ultra-Smooth Surface (for thin film deposition)	Precision Polishing (SCD: Ra < 1 nm; Inch-size PCD: Ra < 5 nm)	Provides atomically smooth surfaces essential for defect control and uniform thin-film growth, improving material consistency compared to the defected G-AAO demonstrated.

Engineering Support & Logistics

6CCVD’s in-house PhD engineering team specializes in diamond material selection and optimization for high-tech applications, including high-performance electrochemical energy storage and advanced sensor design.

Consultation: Our experts can assist researchers in substituting porous G-AAO with a more stable, highly conductive BDD structure, offering superior performance metrics for supercapacitor and biosensor projects.
Global Supply Chain: We ensure reliable, worldwide delivery of high-purity diamond materials using DDU (Delivery Duty Unpaid) default or DDP (Delivery Duty Paid) shipping options.

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/srep19822