Spin Polarization and Magnetic Moment in Silicon Carbide Grown by the Method of Coordinated Substitution of Atoms

At a Glance

Metadata	Details
Publication Date	2021-09-26
Journal	Materials
Authors	С. А. Кукушкін, А. В. Осипов
Institutions	Institute of Problems of Mechanical Engineering
Citations	10
Analysis	Full AI Review Included

Technical Documentation & Analysis: Spin-Polarized Materials for Spintronics

This document analyzes the research on creating stable, spin-polarized silicon vacancies (C₄V centers) in 3C-SiC using the Method of Coordinated Substitution of Atoms (MCSA). 6CCVD leverages its expertise in high-purity, custom-engineered CVD diamond materials (SCD, PCD, BDD) to support and advance research in solid-state spin physics and quantum computing, where these defect engineering techniques are critical.

Executive Summary

Core Achievement: Successful theoretical proposal and experimental implementation of a novel method (MCSA) to create stable silicon vacancies (C₄V centers) in epitaxial 3C-SiC(111) layers.
Defect Engineering: The C₄V center, analogous to the highly studied Nitrogen-Vacancy (NV) center in diamond, acts as a solid-state spin, confirmed by Raman spectroscopy (952 cm^-1 peak).
Magnetic Properties: Density Functional Theory (DFT) modeling confirms that the stable C₄V center possesses a magnetic moment of 1.0 μ_B (Bohr magneton).
Spin Polarization: By controlling the C₄V concentration (n_C4V), the material transitions from a ferromagnetic semiconductor to a half-metallic ferromagnet (up to 100% spin polarization) or a magnetic metal (84% spin polarization).
Methodology: Vacancies are pre-formed in B-doped Si(111) substrates via high-temperature vacuum annealing (~1350 °C) before conversion to 3C-SiC using CO gas, offering a non-irradiation, scalable route for defect creation.
6CCVD Relevance: This research validates the critical role of engineered point defects in wide-bandgap semiconductors for spintronics. 6CCVD provides the industry standard for solid-state spin research: high-purity Single Crystal Diamond (SCD) and custom Boron-Doped Diamond (BDD) substrates.

Technical Specifications

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

Parameter	Value	Unit	Context
SiC Polytype Grown	3C-SiC(111)	N/A	Epitaxial layer on Si(111) substrate
Synthesis Temperature (T)	1350 ± 30	°C	MCSA process temperature range
CO Gas Pressure (p_CO)	80 to 200	Pa	Gas flow parameter
Si Annealing Time (t_a)	1 to 40	min	Controls vacancy concentration (n_C4V)
Epitaxial Layer Thickness (H_SiC)	80 to 600	nm	Dependent on annealing time
Stable Defect Configuration	C₄V Center	N/A	Stable silicon vacancy (V_Si) analog
C₄V Magnetic Moment (μ)	1.0	μ_B	Bohr magneton (DFT calculation for stable state)
Maximum Spin Polarization	100	%	Achieved at n_C4V ≈ 4.2% (System II, half-metallic ferromagnet)
C₄V Raman Shift Signature	952	cm^-1	Experimental confirmation of stable defect
C-C Bond Length (C₄V Cluster)	1.57	Å	Stable state configuration
V_Si to C₄V Energy Barrier	3.33	eV	Transition energy barrier (PBE approximation)

Key Methodologies

The research utilizes the Method of Coordinated Substitution of Atoms (MCSA) combined with preliminary substrate annealing to control defect concentration.

Substrate Pre-Treatment: 3-inch Si(111) substrates, doped with Boron (B), are chemically purified and passivated with hydrogen atoms.
Vacancy Generation: Substrates undergo high-temperature vacuum annealing (T ~1350-1380 °C) for t_a = 1-40 min. This step creates a controlled concentration and penetration depth (0.5-5 µm) of silicon vacancies (V_Si) in the surface layer of the Si substrate.
SiC Conversion (MCSA): Carbon monoxide (CO) gas is introduced (p_CO = 80-200 Pa) at the same high temperature. The Si substrate transforms into 3C-SiC via the chemical reaction: 2Si (crystal) + CO (gas) = SiC (crystal) + SiO (gas) ↑.
Defect Transition and Stabilization: During the high-temperature SiC synthesis, the V_Si defects inherited from the Si substrate transition from a metastable state (μ = 0.8 μ_B) to the stable C₄V configuration (μ = 1.0 μ_B) via a C atom jump. This stable state is achieved rapidly (in < 1 s) at T > 1200 °C.
Characterization: Layers were analyzed using Spectral Ellipsometry (SE), X-ray Diffraction (XRD), Reflected High-Energy Electron Diffraction (RHEED), and Raman Spectroscopy (RS) to confirm thickness, epitaxial quality, and C₄V presence.

6CCVD Solutions & Capabilities

The successful engineering of solid-state spins in SiC highlights the growing demand for highly controlled, wide-bandgap semiconductor materials for quantum technologies. 6CCVD specializes in the production of the most established platform for solid-state qubits: CVD Diamond.

Applicable Materials for Spin Physics Research

The C₄V center in SiC is explicitly compared to the Nitrogen-Vacancy (NV) center in diamond. 6CCVD provides the foundational materials necessary to replicate and advance this class of spintronics research.

6CCVD Material	Relevance to C₄V Research & Spintronics	Key Specifications
High-Purity Single Crystal Diamond (SCD)	Ideal platform for NV and Silicon-Vacancy (SiV) centers, offering superior coherence times and stability compared to SiC defects.	Nitrogen concentration < 1 ppb; Plates up to 10x10 mm; Ra < 1 nm polishing.
Boron-Doped Diamond (BDD)	Analogous to the B-doped Si substrate used in the paper. BDD allows for controlled p-type conductivity, crucial for charge state control of quantum defects.	Custom doping levels (heavy to light); Available in SCD or PCD formats.
Polycrystalline Diamond (PCD)	Suitable for large-area sensor applications or high-power thermal management where defect engineering is required across large wafers.	Wafers up to 125 mm diameter; Thickness up to 500 µm.

Customization Potential for Defect Engineering

The paper demonstrates the need for precise control over thin film thickness (80 nm to 600 nm) and specific substrate doping. 6CCVD offers unparalleled customization capabilities essential for advanced defect research:

Research Requirement	6CCVD Capability	Technical Advantage
Thickness Control	SCD/PCD thickness from 0.1 µm up to 500 µm. Substrates up to 10 mm.	Enables precise epitaxial growth and thin-film device fabrication, matching or exceeding the thickness control demonstrated in the SiC paper.
Surface Quality	SCD polishing to Ra < 1 nm. Inch-size PCD polishing to Ra < 5 nm.	Essential for high-quality epitaxial layers, RHEED analysis, and minimizing surface-related decoherence in quantum devices.
Custom Metalization	In-house deposition of Au, Pt, Pd, Ti, W, Cu.	Supports the integration of magnetic contacts and electrodes required for half-metallic ferromagnet devices and spintronic architectures.
Custom Dimensions	SCD plates up to 10x10 mm. PCD wafers up to 125 mm (5 inches).	Provides scalability for large-area spintronic devices and commercial production.

Engineering Support

The successful creation of C₄V centers relies heavily on DFT modeling and precise control of growth parameters (temperature, pressure, gas composition).

6CCVD’s in-house PhD team specializes in MPCVD growth and defect engineering in diamond. We offer comprehensive material consultation to assist researchers in selecting the optimal diamond material (SCD, PCD, BDD) and growth recipe for similar solid-state spin and quantum computing projects, ensuring maximum defect yield and coherence time.

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

View Original Abstract

In the present work, a new method for obtaining silicon carbide of the cubic polytype 3C-SiC with silicon vacancies in a stable state is proposed theoretically and implemented experimentally. The idea of the method is that the silicon vacancies are first created by high-temperature annealing in a silicon substrate Si(111) doped with boron B, and only then is this silicon converted into 3C-SiC(111), due to a chemical reaction with carbon monoxide CO. A part of the silicon vacancies that have bypassed “chemical selection” during this transformation get into the SiC. As the process of SiC synthesis proceeds at temperatures of ~1350 °C, thermal fluctuations in the SiC force the carbon atom C adjacent to the vacancy to jump to its place. In this case, an almost flat cluster of four C atoms and an additional void right under it are formed. This stable state of the vacancy, by analogy with NV centers in diamond, is designated as a C4V center. The C4V centers in the grown 3C-SiC were detected experimentally by Raman spectroscopy and spectroscopic ellipsometry. Calculations performed by methods of density-functional theory have revealed that the C4V centers have a magnetic moment equal to the Bohr magneton μB and lead to spin polarization in the SiC if the concentration of C4V centers is sufficiently high.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma14195579

References

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