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6CCVD Research

Shallow NV centers augmented by exploiting n-type diamond

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2021-03-10
JournalCarbon
AuthorsAya Watanabe, Tetsuri Nishikawa, Hiromitsu Kato, Masahiro Fujie, Masanori Fujiwara
InstitutionsKyoto University, National Institute of Advanced Industrial Science and Technology
Citations34
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”
  • Core Achievement: Demonstrated significant enhancement of spin-coherence time (T2), charge state stability, and creation yield for shallow Nitrogen-Vacancy (NV) centers (~15 nm depth) formed by ion implantation into phosphorus-doped n-type diamond.
  • T2 Extension: The average T2 in the n-type diamond (325.7 ”s) was over 1.7 times longer than in the non-doped reference diamond (184.6 ”s). The longest T2 measured (579.0 ”s) approaches the theoretical limit imposed by the natural abundance 13C nuclear spin bath (~0.6 ms).
  • Defect Suppression Mechanism: The extension of T2 is attributed to the suppression of paramagnetic defects (like multi-vacancy or vacancy-impurity complexes) generated during ion implantation, achieved through Coulomb repulsion provided by the charged defects in the n-type material.
  • Creation Yield Improvement: The density of created 15NV centers improved by more than twofold in the phosphorus-doped sample compared to the non-doped reference, confirming the effectiveness of defect-charging during implantation.
  • Charge State Stabilization: While the average NV- population ratio was similar between samples (~0.74), the n-type diamond showed a significant population of highly stable centers (8 out of 78 measured centers had an NV- population > 0.8), supporting the stabilization effect.
  • Significance: These enhancements, achieved within a diamond semiconductor platform, are critical for the development and nano-fabrication of future integrated quantum devices, sensing, and spintronic applications.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
NV Center Depth (Peak)~15nmSimulated depth via SRIM
Longest T2 (P-doped, Sample I)579.0 ± 28.7”sShallow NV center performance
Average T2 (P-doped, Sample I)325.7 ± 148.2”s1.7x improvement over non-doped reference
Average T2 (Non-doped, Sample II)184.6 ± 76.5”sReference sample performance
T2 Limiting Factor (Bulk)~0.6msLimited by natural abundant 13C nuclear spins
15N Ion Implantation Energy10keVUsed for shallow NV creation
15NV Creation Density (Sample I)(27.5 ± 17.1) / 100”m2More than twofold improvement
Phosphorus Concentration (Sample I)5 x 1016cm-3CVD grown n-type layer
P-doped Layer Thickness7 x 102nmCVD grown layer
Average NV- Population Ratio (Sample I)0.746 ± 0.017N/ACharge state stability (NV-/NV0)
Highest Observed NV- Population (Sample I)0.92N/ASingle NV center measurement
P1 Center Concentration (Sample II)(2.6 ± 0.1) x 1016cm-3Estimated via EPR (~0.14 ppm)
Annealing Temperature800°CPost-implantation NV creation
13C Natural Abundance1.1%Used in methane source gas

Key Methodologies

Section titled “Key Methodologies”
  1. Material Growth: A thin film of phosphorus-doped n-type diamond (Sample I) was grown onto a IIa (111) HPHT diamond substrate using microwave plasma-enhanced Chemical Vapor Deposition (CVD).
  2. Doping Specification: The CVD process targeted a phosphorus concentration of 5 x 1016 cm-3 and a layer thickness of approximately 700 nm. Methane with natural 13C abundance (1.1%) was used.
  3. Reference Sample: Sample II was a pure IIa (111) HPHT diamond, serving as a non-doped reference.
  4. Ion Implantation: Nitrogen isotope (15N) ions were simultaneously implanted into both samples to create shallow NV centers.
    • Kinetic Energy: 10 keV.
    • Implantation Temperature: 600 °C.
    • Implanted Density: ~5 x 108 atoms cm-2.
  5. Depth Simulation: The peak depth of the 15N ions was simulated to be around 15 nm using the ion-implantation Monte-Carlo simulator (SRIM).
  6. Annealing and Cleaning: Samples were annealed at 800 °C for 30 minutes, followed by washing with hot acid to remove surface contaminants.
  7. Spin Coherence Measurement (T2): T2 was measured using Hahn-echo sequences, applying a static magnetic field of 3.2 mT. Acoustic optical modulators were used to suppress background illumination.
  8. Charge State Stability Measurement: Nondestructive single-shot charge-state measurements were performed using weak 593-nm laser irradiation (3-”W) to observe stochastic transitions between NV0 and NV-.
  9. NV Density Measurement: The NV creation yield was determined by counting the number of 15NV centers observed via confocal microscopy in a unit area.

Commercial Applications

Section titled “Commercial Applications”
  • Integrated Quantum Processors: The ability to create high-quality, shallow NV centers in a semiconductor (n-type diamond) matrix is essential for integrating spin qubits with electronic and photonic components on a chip.
  • Nanoscale Quantum Sensing: Extended T2 times directly translate to higher sensitivity and resolution for diamond-based quantum sensors used in magnetic field, electric field, and temperature measurements at the nanometer scale.
  • High-Resolution NMR/ESR: Shallow NV centers with long coherence times are critical for performing nanoscale nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy, enabling chemical structure analysis of minute samples.
  • Spintronics: Utilizing the stable spin properties of NV centers in the n-type diamond platform for developing novel room-temperature spintronic devices and memory elements.
  • Single-Photon Sources: Improved creation yield and stable NV- charge state enhance the efficiency and reliability of diamond-based light-emitting diodes (LEDs) and single-photon sources required for quantum communication.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2017 - Nanoscale nuclear magnetic resonance with chemical resolution [Crossref]
  2. 2017 - Submillihertz magnetic spectroscopy performed with a nanoscale quantum sensor [Crossref]
  3. 2017 - Quantum sensing with arbitrary frequency resolution [Crossref]
  4. 2013 - Nanoscale nuclear magnetic resonance with a nitrogen-vacancy spin sensor [Crossref]
  5. 2014 - Subnanometre resolution in three-dimensional magnetic resonance imaging of individual dark spins [Crossref]
  6. 2014 - Nanoscale imaging and control of domain-wall hopping with a nitrogen-vacancy center microscope [Crossref]
  7. 2017 - Nanomechanical sensing using spins in diamond [Crossref]
  8. 2019 - Ultra-long coherence times amongst room-temperature solid-state spins [Crossref]
  9. 2015 - Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres [Crossref]
  10. 2010 - Quantum entanglement between an optical photon and a solid-state spin qubit [Crossref]

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