Fabrication and quantum sensing of spin defects in silicon carbide

At a Glance

Metadata	Details
Publication Date	2023-09-26
Journal	Frontiers in Physics
Authors	Qin‐Yue Luo, Qiang Li, Junfeng Wang, Pei‐Jie Guo, Wu-Xi Lin
Institutions	Zhejiang University, University of Science and Technology of China
Citations	19
Analysis	Full AI Review Included

Executive Summary

This review details the fabrication and quantum sensing capabilities of spin defects (color centers) in Silicon Carbide (SiC) for engineering and quantum technology applications.

Platform Advantage: SiC is a mature, wide-bandgap semiconductor compatible with inch-scale growth and micro/nano-fabrication, offering room-temperature stable spin control.
Key Defects: The primary spin defects studied are Silicon-Vacancy (V_Si), Divacancy (VV), and Nitrogen-Vacancy (NV) centers, all controllable by laser and microwave.
Advanced Fabrication: Efficient single-defect generation is achieved using four main methods: high-energy irradiation, patterned ion implantation (for arrays), focused ion beam (FIB) implantation (for 3D control), and femtosecond laser writing (for minimal lattice damage).
Exceptional Coherence: Divacancy centers in isotopically purified SiC demonstrate spin coherence times (T₂) exceeding 5 seconds, making them highly competitive solid-state qubits.
High-Sensitivity Sensing: SiC defects are utilized for multi-parameter quantum sensing, achieving nanotesla (nT) sensitivity for magnetic fields and millikelvin (mK) sensitivity for temperature.
Extreme Environment Capability: The V_Si center is proven to be an excellent quantum sensor for in situ magnetic detection and thermometry under extreme high-pressure conditions (up to 36 GPa).

Technical Specifications

Parameter	Value	Unit	Context
Si-Vacancy (V2) ZPL	915	nm	4H-SiC polytype
Si-Vacancy (V2) ZFS (D)	35	MHz	Ground state
Divacancy (VV) T₂ Coherence Time	> 5	s	Isotopically purified SiC sample
Magnetic Field Sensitivity (Optimized)	3.5	nT/Hz^1/2	VV centers, optimized ODMR
Temperature Sensitivity (TCPMG)	13.4	mK/Hz^1/2	PL6 Divacancy center
Temperature ZFS Slope (PL5)	-109.5	kHz/K	Near room temperature
Pressure ZFS Slope (V_Si)	0.31	MHz/GPa	High pressure sensing
Pressure Sensing Sensitivity (VV)	0.28	MPa/Hz^1/2	Divacancy ensemble
NV Center Polarization Degree	~90	%	c-axis oriented
V_Si Generation Yield (C+ Implantation)	78 ± 5	%	After 600°C annealing
V_Si Photonic Crystal Purcell Enhancement	80	-fold	Selective ZPL enhancement
High-Pressure Operating Range	Up to 36.1	GPa	VV center sensing limit

Key Methodologies

The fabrication of single and ensemble spin defects in SiC relies on precise control of vacancy generation and subsequent thermal processing.

1. Defect Generation via Irradiation

Method: High-energy (e.g., 2 MeV) electron or neutron irradiation creates Si and C vacancies uniformly throughout the sample.
Process: Vacancies migrate and form divacancies (VV) or silicon vacancies (V_Si) during post-irradiation annealing.
Annealing Parameters:
- V_Si: Annealing at 600°C.
- VV: Annealing at 750°C or 850°C for 30 min in Argon (Ar) gas.
- NV: Annealing at 900°C (for proton irradiation) or 1000°C (optimal for ensemble).

2. Patterned Ion Implantation

Purpose: Enables predetermined location fabrication of color centers, often used for creating arrays.
Masking: Polymethyl methacrylate (PMMA) layer (hundreds of nm thick) deposited via spin coating, patterned using Electron-Beam Lithography (EBL).
Ions Used: Carbon (C⁺), Hydrogen (H⁺), Helium (He²⁺).
V_Si Array Recipe (C⁺): 30 keV C⁺ implantation followed by annealing at 600°C for 1 h, increasing conversion yield to ~78%.

3. Focused Ion Beam (FIB) Implantation

Advantage: Maskless method for three-dimensional (3D) defect engineering with nanometer resolution.
Control: Depth determined by ion energy (simulated via SRIM); lateral distribution controlled by beam focusing and residence time.
Ions Used: Hydrogen (H⁺, 1.7 MeV), Silicon (Si²⁺, 35 keV), Helium (He²⁺, 30 keV).
Conversion Yield: Achieves V_Si generation rates of 35% to 38% for focused He²⁺ and Si²⁺ beams, respectively.

4. Femtosecond (fs) Laser Writing

Advantage: Minimizes residual lattice damage compared to ion methods.
Setup: Femtosecond pulsed laser (e.g., 790 nm, 250 fs duration) focused onto the SiC sample fixed on a high-precision translation stage.
Results: Achieves optically stable single V_Si yield up to 30% and lateral position accuracy of 80 nm without post-annealing.

5. Quantum Sensing Techniques

Magnetic/Temperature/Pressure Sensing: Primarily uses Optically Detected Magnetic Resonance (ODMR) to measure shifts in the Zero-Field Splitting (ZFS, D) or Zeeman splitting.
High Sensitivity: Achieved using pulsed ODMR sequences (Ramsey, TCPMG) and optimizing laser/microwave power to reduce power broadening.
Electric Field/Strain Sensing: Measured via the Stark effect, observing changes in the spin Hamiltonian parameters (D, E_x,y) induced by the electric field or strain.

Commercial Applications

The unique properties of SiC spin defects—especially their near-infrared fluorescence and compatibility with semiconductor manufacturing—make them suitable for several high-tech sectors.

Quantum Information Processing:
- Qubit Registers: Utilizing the long coherence times of VV centers (up to 5 s) for building robust solid-state quantum registers.
- Quantum Networks: Near-infrared fluorescence (telecom range) of VV and V_Si centers is ideal for long-distance spin-photon entanglement and quantum communication infrastructure.
Advanced Quantum Sensing:
- Nanoscale Magnetometry: High-sensitivity (nT range) magnetic field sensing for characterizing magnetic materials, integrated circuits, and biological samples.
- Thermometry in Electronics: SiC-based thermometers capable of operating at high temperatures (above 550 K) to monitor internal temperatures of SiC power devices and high-power RF components.
- Extreme Condition Metrology: In situ sensing of magnetic fields and temperature inside Diamond Anvil Cells (DACs) at pressures up to 36 GPa, crucial for high-pressure physics and materials discovery (e.g., superconductivity research).
Integrated Photonics and Electronics:
- On-Chip Quantum Devices: Integration of color centers into nano-fabricated structures like waveguides, solid immersion lenses, and photonic crystal cavities to enhance photon collection efficiency and enable scalable quantum photonics.
- SiC Power Devices: Leveraging SiC’s mature fabrication base to integrate quantum sensors directly into high-power electronic devices for real-time monitoring of temperature and electric fields.

View Original Abstract

In the past decade, color centers in silicon carbide (SiC) have emerged as promising platforms for various quantum information technologies. There are three main types of color centers in SiC: silicon-vacancy centers, divacancy centers, and nitrogen-vacancy centers. Their spin states can be polarized by laser and controlled by microwave. These spin defects have been applied in quantum photonics, quantum information processing, quantum networks, and quantum sensing. In this review, we first provide a brief overview of the progress in single-color center fabrications for the three types of spin defects, which form the foundation of color center-based quantum technology. We then discuss the achievements in various quantum sensing, such as magnetic field, electric field, temperature, strain, and pressure. Finally, we summarize the current state of fabrications and quantum sensing of spin defects in SiC and provide an outlook for future developments.

Tech Support

Original Source

DOI: https://doi.org/10.3389/fphy.2023.1270602

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