Vertical-Substrate MPCVD Epitaxial Nanodiamond Growth

At a Glance

Metadata	Details
Publication Date	2017-02-09
Journal	Nano Letters
Authors	Yan‐Kai Tzeng, Jingyuan Linda Zhang, Haiyu Lu, Hitoshi Ishiwata, Jeremy Dahl
Institutions	Stanford University, Justus-Liebig-Universität Gießen
Citations	77
Analysis	Full AI Review Included

Vertical-Substrate MPCVD Nanodiamond Growth Analysis: Leveraging Gradients for Quantum Material Synthesis

This documentation analyzes the technical feasibility and commercial implications of the research paper “Vertical-Substrate MPCVD Epitaxial Nanodiamond Growth,” focusing on its relevance to 6CCVD’s capabilities in custom MPCVD diamond production for quantum technology and bio-sensing.

Executive Summary

The analyzed research introduces a novel, high-efficiency MPCVD geometry—the vertical substrate orientation—to rapidly optimize the growth of ultra-high-quality single-crystal nanodiamonds containing desirable color centers.

Novel Methodology: Utilized a vertical MPCVD stage orientation to generate continuous, predictable gradients in temperature, plasma density, and atomic hydrogen concentration across the substrate.
Rapid Optimization: This gradient method allowed for the simultaneous screening of a wide parameter space, resulting in the rapid identification of conditions yielding optimal crystal quality.
Achieved Nanodiamond Quality: Successfully grew single-crystal diamonds down to 10 nm in size, with optically active Silicon-Vacancy (Si-V) centers in particles as small as 75 nm.
High Crystalline Purity: Demonstrated ultra-high quality, achieving sp³ Raman peak Full Width at Half Maximum (FWHM) as low as 3.51 cm^-1, approaching the theoretical standard of bulk diamond (3.0 cm^-1).
In-Situ Doping: Successfully incorporated Si-V and Cr-related centers during growth by introducing dopant sources (SiH₄ or Chromium salt solution) into the plasma environment, bypassing damaging ion irradiation techniques.
Low-Temperature Growth: Optimized growth occurs at significantly lower stage temperatures (300 °C - 350 °C) compared to conventional MPCVD, favorable for delicate nanodiamond seeds (pentamantane diamondoids).

Technical Specifications

The following table summarizes the key hard data points extracted from the optimized growth conditions and resulting material characteristics.

Parameter	Value	Unit	Context
Smallest Single Crystal Size	10	nm	Minimum diameter achieved using vertical growth
Optically Active Si-V Size	75	nm	Diameter of single-crystal nanodiamonds showing Si-V centers
Raman FWHM (Highest Quality)	3.51	cm^-1	Narrowest sp³ line-width observed (bulk standard is 3.0 cm^-1)
Standard Stage Temperature	350	°C	Used for initial growth optimization
Si-V Stage Temperature (Optimized)	300 - 330	°C	Used for growth on Nitrogen-doped 6H-SiC
Microwave Power (Si-V Optimization)	300	W	Used for optically characterized nanodiamonds
Operating Pressure	23	Torr	Consistent system pressure
Substrate Temperature Gradient (Measured)	550 to 750	°C	Measured along the vertical axis (2 mm to 5 mm height)
Hydrogen Flow Rate (H₂)	300	sccm	Used in all primary experiments
Methane Flow Rate (CH₄)	0.5	sccm	Base carbon source flow rate
Si-V Doping Method	1% SiH₄ in CH₄ feed gas or SiC substrate etching	-	In situ Silicon incorporation
Cr Center Photoluminescence Peaks	750, 758	nm	Optical signature of Chromium-related centers
Si-V Center Radiative Lifetime	0.602 ± 0.008	ns	Measured at room temperature (ND 1)
Substrate Material Used	N-type <100> Si or N-doped 6H-SiC	-	Substrate must be semiconducting to act as plasma antenna

Key Methodologies

The experiment relies on a unique combination of seed preparation and MPCVD configuration to achieve epitaxial growth of doped nanodiamonds.

Seed Layer Preparation: A self-assembled monolayer of [1(2,3)4] pentamantane diamondoids (molecular-sized diamonds, 0.5 to 1.0 nm) was chemically bonded to the oxidized surface of the semiconducting substrate (Silicon or Nitrogen-doped Silicon Carbide) via phosphonate linkages.
Vertical Chamber Orientation: The prepared substrate wafer (e.g., 8 mm high, 6 mm wide, 0.5 mm thick Si) was rotated 90° and stood vertically on a molybdenum holder within the MPCVD chamber.
Gradient Generation: The vertical configuration forced systematic variations in growth conditions, including local temperature (T), plasma density, and, crucially, atomic hydrogen density (H), allowing for high-throughput optimization.
Optimal Growth Zone Identification: High-quality, pure sp³ single-crystal nanodiamonds were found near the bottom of the vertically oriented wafer, corresponding to regions of lower temperature (~600 °C) and higher atomic hydrogen concentration (which acts as an sp² etchant).
Color Center Introduction:
- Si-V: Silicon dopants were sourced either directly from the etching of the Si/SiC substrate or by introducing 1% silane (SiH₄) mixed with the methane precursor into the plasma phase.
- Cr-related: Chromium centers were introduced via a precursor solution, Cr(H₂O)₆₃, dried directly onto the substrate before growth, confirming the method’s versatility for metal/rare earth element doping.

6CCVD Solutions & Capabilities: Enabling Advanced Color Center Engineering

This research underscores the critical need for precisely controlled, ultra-high-purity diamond materials and customized growth platforms for next-generation quantum technologies. 6CCVD is uniquely positioned to supply the foundational materials and engineering services required to replicate and scale this vertical growth methodology.

Applicable Materials for Quantum Applications

To replicate or extend this quantum nanodiamond research, high-quality, pre-doped, or ultra-pure substrates are necessary.

Optical Grade SCD: Essential for subsequent high-power confocal microscopy and quantum measurements. Our Single Crystal Diamond (SCD) plates (thickness up to 500 µm) provide the perfect, low-strain material required for fundamental studies of color center coherence and optical stability.
Custom Doped Diamond: While the paper used N-doped SiC as a low-quenching substrate, 6CCVD offers Custom Doped MPCVD Diamond (BDD, N-doped, or co-doped) tailored specifically to reduce background photoluminescence and enhance target color center formation (e.g., Si-V or Ge-V) directly within the diamond matrix.

Customization Potential for Novel CVD Techniques

The vertical growth geometry requires non-standard substrate dimensions and holder fixtures, which fall directly within 6CCVD’s core engineering capabilities.

Research Requirement	6CCVD Customization Service	Technical Benefit
Non-Standard Substrate Size	Custom Dimensions: Plates/wafers up to 125mm, cut to exacting shapes (e.g., 8 mm x 6 mm vertical antennae).	Facilitates precise replication of the vertical MPCVD geometry for gradient optimization and scalability studies.
Surface Quality	Precision Polishing: Achieved Ra < 1nm for SCD and Ra < 5nm for inch-size PCD.	Ensures an atomically flat surface crucial for the uniform chemical bonding of nanodiamondoid seeds (pentamantane) and stress-free epitaxial growth.
Material Incorporation	Controlled Doping: Expertise in adding Silicon, Germanium, Nickel, or Nitrogen precursors in situ during MPCVD.	Allows engineers to move beyond surface drying (used for Cr) to create highly uniform concentration profiles of desired color centers (Ge-V, Si-V, Ni-related centers) across larger wafers.
Device Integration	Advanced Metalization: Internal capability for deposition of Au, Pt, Pd, Ti, W, and Cu electrodes.	Enables the integration of the vertical diamond structures with microwave circuitry or electrical contacts necessary for advanced qubit control and sensing applications (as referenced for N-V centers).

Engineering Support & Sales Incentive

6CCVD’s in-house PhD material science team has deep experience in high-purity MPCVD growth, specializing in defect engineering and surface termination.

Targeted Consultation: 6CCVD’s engineering team can assist researchers and technical clients with material selection and optimization for similar quantum computing, bio-sensing, and quantum networking projects requiring high-coherence color centers (Si-V, Cr-related, Ge-V, N-V).
Scalability Studies: We provide material solutions—from nanodiamond seed material to large PCD wafers (up to 125mm)—allowing clients to transition successful small-scale vertical growth recipes to mass-producible wafer processes.
Global Logistics: We provide reliable Global Shipping (DDU default, DDP available) ensuring high-value, time-sensitive quantum materials reach labs worldwide without delay.

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

View Original Abstract

Color center-containing nanodiamonds have many applications in quantum technologies and biology. Diamondoids, molecular-sized diamonds have been used as seeds in chemical vapor deposition (CVD) growth. However, optimizing growth conditions to produce high crystal quality nanodiamonds with color centers requires varying growth conditions that often leads to ad-hoc and time-consuming, one-at-a-time testing of reaction conditions. In order to rapidly explore parameter space, we developed a microwave plasma CVD technique using a vertical, rather than horizontally oriented stage-substrate geometry. With this configuration, temperature, plasma density, and atomic hydrogen density vary continuously along the vertical axis of the substrate. This variation allowed rapid identification of growth parameters that yield single crystal diamonds down to 10 nm in size and 75 nm diameter optically active center silicon-vacancy (Si-V) nanoparticles. Furthermore, this method may provide a means of incorporating a wide variety of dopants in nanodiamonds without ion irradiation damage.

Tech Support

Original Source

DOI: https://doi.org/10.1021/acs.nanolett.6b04543