Nitrogen and Silicon Defect Incorporation during Homoepitaxial CVD Diamond Growth on (111) Surfaces

At a Glance

Metadata	Details
Publication Date	2015-01-01
Journal	MRS Proceedings
Authors	Samuel Moore, Yogesh K. Vohra
Institutions	University of Alabama at Birmingham
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Quantum Sensing

This document analyzes the research on defect incorporation in (111)-oriented CVD diamond, highlighting 6CCVD’s capabilities in supplying the specialized materials required for next-generation quantum computing and nanoscale magnetometry applications.

Executive Summary

Core Application Validation: The research confirms the viability of homoepitaxial (111)-Single Crystal Diamond (SCD) growth for creating highly oriented Nitrogen-Vacancy (N-V) and Silicon-Vacancy (Si-V) color centers, essential for quantum computing (qubits) and highly sensitive magneto-sensors.
Defect Control Achieved: Precise control over N-V (575nm, 637nm ZPL) and Si-V (737nm ZPL) defect incorporation was demonstrated by manipulating trace amounts of nitrogen (0-1500 ppm) and oxygen in the MPCVD plasma.
Nitrogen Threshold Identified: Nitrogen was found to enhance silicon incorporation, suggesting a critical threshold concentration above which it may become inhibitive to Si-V formation.
Oxygen Trade-offs: Oxygen suppresses Si-V incorporation but negatively impacts crystal quality, leading to reduced growth rates, increased surface twinning (protrusions up to 400nm), and the formation of detrimental sp² carbon deposits.
Material Challenge: Successful industrialization of this technology hinges on overcoming the inherent difficulties of growing high-quality, low-twinning (111)-SCD films and obtaining superior seed substrates.
6CCVD Value Proposition: 6CCVD specializes in providing the high-quality, custom-oriented SCD substrates and precision doping control necessary to minimize surface defects and optimize N-V alignment for advanced quantum applications.

Technical Specifications

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

Parameter	Value	Unit	Context
Substrate Orientation	(111)	Crystal Plane	Homoepitaxial growth on HPHT Type Ib seeds
Seed Off-Cut Angle	3	Degrees	Plates produced by Sumitomo
MPCVD Power Range	900 - 1180	W	Adjusted to maintain target temperature
Target Temperature	950 ± 15	°C	Substrate temperature during growth
Pressure Range	70 - 91	Torr	Varied to maintain constant temperature
Total Gas Flow Rate	400	sccm	Maintained during deposition
Nitrogen Concentration Range	0 - 1500	ppm	Varied in plasma (0% to 0.15% relative to total gas)
N-V° ZPL	575	nm	Photoluminescence Zero Phonon Line (2.156 eV)
N-V⁻ ZPL	637	nm	Photoluminescence Zero Phonon Line (1.945 eV)
Si-V ZPL	737	nm	Photoluminescence Zero Phonon Line (1.681 eV)
Maximum Surface Twin Height	~400	nm	Observed protrusion height on B1P1 (AFM data)
Approximate Growth Rate	2 - 15	µm/hour	Measured via cross-sectional SEM
Diamond Raman Peak	1332	cm⁻¹	Indicates high crystal quality (low sp² content)

Key Methodologies

The experiment focused on controlling defect incorporation via gas phase chemistry during MPCVD growth on (111)-SCD substrates.

Substrate Selection: Six Type Ib (111)-oriented HPHT SCD plates (3° off-cut) were used as seed crystals, confirmed via X-ray diffraction (XRD).
CVD Setup: Growth was performed using a 1.2 kW magnetron tunable 2.45 GHz Microwave Plasma CVD (MPCVD) system.
Gas Chemistry: Process gases included H₂, N₂, O₂, and CH₄. Total flow rate was fixed at 400 sccm.
Growth Parameters: Substrate temperature was maintained near 950 °C using a two-color pyrometer. Chamber pressure (70-91 Torr) and magnetron power (900-1180 W) were dynamically adjusted to stabilize temperature.
Impurity Variation: Nitrogen concentration was systematically varied between 0 and 1500 ppm. Oxygen was introduced in specific runs (up to 0.1%) to study its inhibitory effect on silicon incorporation (silicon originating from the quartz bell jar).
Post-Growth Treatment: All plates underwent hydrogen plasma etching to remove surface graphitic and amorphous carbon.
Characterization: Epitaxial quality and impurity incorporation were assessed using:
- Photoluminescence (PL) and Raman Spectroscopy (532nm YAG laser excitation).
- X-ray Photoelectron Spectroscopy (XPS) for elemental composition.
- Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for surface morphology and twin analysis.

6CCVD Solutions & Capabilities

This research underscores the critical need for highly controlled, low-defect (111)-SCD material. 6CCVD is uniquely positioned to address the challenges identified in this study, providing materials optimized for quantum sensing and magnetometry.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage
High-Quality (111) Substrates	Optical Grade SCD (Single Crystal Diamond)	We supply high-purity SCD substrates with precise crystallographic orientation, minimizing the dislocations and stacking faults common in HPHT (111) seeds.
Twinning Suppression & Surface Morphology	Ultra-Low Roughness Polishing (Ra < 1nm)	The paper noted surface twins up to 400nm high. 6CCVD guarantees SCD polishing to Ra < 1nm, essential for maximizing optical accessibility and spatial resolution in nanoscale sensors.
Controllable Defect Density	Precision Gas Doping & MPCVD Recipe Control	Our advanced MPCVD reactors allow for the precise introduction and monitoring of N₂ and O₂ at ppm levels, ensuring reproducible N-V and Si-V densities and controlled alignment along the <111> axis.
Custom Dimensions & Geometry	Large Area & Custom Fabrication Services	We offer SCD plates up to 500µm thick and PCD wafers up to 125mm in diameter. We provide custom laser cutting services to achieve precise, reproducible geometries, eliminating the material waste associated with traditional cleaving/polishing of (111) faces.
Device Integration	In-House Metalization Services	For integrating N-V sensors with microwave or readout circuitry, 6CCVD offers internal metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu deposition, directly onto the diamond surface.

Engineering Support

6CCVD’s in-house PhD team can assist researchers in optimizing CVD growth recipes to minimize the detrimental “alpha parameter” (related to the V<100>/V<111> growth velocity ratio), thereby suppressing surface twinning and enhancing the epitaxial quality of (111)-SCD films. This support is crucial for projects focused on Quantum Sensing and Magnetometry requiring high spatial resolution and long spin coherence times.

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

Tech Support

Original Source

DOI: https://doi.org/10.1557/opl.2015.304