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6CCVD Research

Nitrogen-Vacancy Color Centers Created by Proton Implantation in a Diamond

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2021-02-09
JournalMaterials
AuthorsMariusz Mrózek, Mateusz Schabikowski, Marzena Mitura‐Nowak, Janusz Lekki, M. MarszaƂek
InstitutionsJagiellonian University, Institute of Nuclear Physics, Polish Academy of Sciences
Citations19
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study investigates the controlled creation and spin relaxation properties of negatively charged Nitrogen-Vacancy (NV-) color centers in diamond using high-energy proton implantation.

  • Controlled NV- Creation: NV- ensembles were successfully created in Type Ib HPHT diamond ([N] ~ 50 ppm) using 1.8 MeV proton implantation, followed by 900 °C vacuum annealing.
  • Depth Specificity: The high-energy proton beam generated vacancies primarily in a narrow layer peaking sharply at approximately 20 ”m depth, enabling spatial control over NV- layer formation.
  • Dose Dependence: Implantation doses ranged widely from 1.5 x 1013 to 1.5 x 1017 ions/cm2, allowing for the tailoring of NV concentration and defect density.
  • Spin Relaxation Analysis: Both longitudinal (T1) and transverse (T2) spin relaxation rates increased linearly (on a logarithmic scale) with implantation dose, confirming that defect density limits spin lifetime.
  • Performance Range: Measured T1 times decreased from 6 ms to 1.25 ms, and T2 times decreased from 2.5 ”s to 1.1 ”s across the tested dose range.
  • Limitation Identified: The highest implantation doses (1.5 x 1017 ions/cm2) caused significant crystal damage, leading to a drop in fluorescence signal and ODMR contrast, limiting the maximum useful dose.
  • Engineering Value: The technique is versatile for preparing microscale NV sensors, particularly thin, dense layers required for high-sensitivity magnetometry and bio-sensing applications.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Diamond TypeType Ib mono-crystalline HPHTN/A(100)-oriented, Element Six source
Initial Nitrogen Concentration~50ppmConcentration in the bulk diamond matrix
Implantation ParticleProton (H+)N/AUsed to create lattice vacancies
Implantation Energy1.8MeVEnergy of the focused proton beam
Implantation Depth (Peak Vacancy)~20”mDepth profile simulated using SRIM 2013
Implantation Dose Range1.5 x 1013 to 1.5 x 1017ions/cm2Range tested across 8 spots
Annealing Temperature900°CPerformed in vacuum to stimulate vacancy migration
Annealing Time2hDuration of post-implantation thermal treatment
Longitudinal Relaxation Time (T1) Range6 to 1.25msDecreases with increasing dose
Transverse Relaxation Time (T2) Range2.5 to 1.1”sDecreases with increasing dose
T1 Rate Dependence Slope0.16N/ASlope of 1/T1 vs. dose (logarithmic scale)
T2 Rate Dependence Slope0.08N/ASlope of 1/T2 vs. dose (logarithmic scale)
Displacement Threshold Energy37.5eVUsed in SRIM simulation for (100) direction
ODMR ContrastDecreases%Drop observed at highest implantation doses
Microwave Pi Pulse Length50nsUsed for T1 and T2 measurements

Key Methodologies

Section titled “Key Methodologies”

The NV- creation and characterization process involved precise material selection, controlled implantation, thermal processing, and advanced optical/spin measurements:

  1. Sample Acquisition and Selection: Two 3.0 x 3.0 x 0.3 mm3 Type Ib HPHT diamond samples (HEN1 and HEN2) with an initial nitrogen concentration of ~50 ppm were used.
  2. Proton Implantation: Protons were implanted on the polished side using a Van de Graaff accelerator at 1.8 MeV. The beam spot diameter was approximately 20 ”m. Eight distinct spots were implanted across the two samples, covering doses from 1013 to 1017 ions/cm2.
  3. Thermal Annealing: Samples were annealed in a vacuum system at 900 °C for 2 hours to promote vacancy diffusion and association with nitrogen atoms, forming NV centers.
  4. Optical Characterization (PL/Raman): Fluorescence spectra (PL) were collected using a confocal microscope setup (532 nm green laser excitation) to confirm NV center formation (Zero Phonon Line at 637 nm). Raman spectroscopy was used to assess crystal damage.
  5. Optically Detected Magnetic Resonance (ODMR): ODMR contrast measurements were performed to assess the quality and density of the NV ensembles.
  6. Longitudinal Relaxation (T1) Measurement: T1 was measured using the “relaxation in the dark method,” employing a sequence of optical polarization and microwave pulses.
  7. Transverse Relaxation (T2) Measurement: T2 (phase coherence time) was measured using the Hahn spin-echo sequence, utilizing a microwave π pulse length of 50 ns.

Commercial Applications

Section titled “Commercial Applications”

The ability to create dense, thin, and spatially controlled layers of NV- centers with characterized spin properties is critical for several emerging quantum and sensing technologies:

  • Quantum Magnetometry: NV ensembles are used as highly sensitive magnetic field sensors. Dense, thin layers maximize the signal (sensitivity scales as (NsT2)-1/2), crucial for wide-field magnetic imaging.
  • Bio-Magnetometry and Imaging: Using NV layers in thin diamond plates for nanoscale sensing and imaging of magnetic fields generated by living cells or biological systems.
  • Quantum Information Processing: The phase coherence time (T2) constrains the minimum gate operation time, making materials with optimized T2 essential for diamond-based quantum computing architectures.
  • Temperature Sensing: NV centers act as robust, localized temperature probes, useful in microscale thermal management and biological environments.
  • Integrated Circuit (IC) Current Imaging: Thin NV layers can be used for high-resolution imaging of current flow in integrated circuits.
  • Shallow NV Layer Fabrication: The proton implantation technique, while creating deep vacancies (~20 ”m), provides a foundation for creating relatively uniform NV depth profiles in thin nitrogen-doped layers (0.1-10 ”m) overgrown on high-quality diamond substrates.
View Original Abstract

We present an experimental study of the longitudinal and transverse relaxation of ensembles of negatively charged nitrogen-vacancy (NV−) centers in a diamond monocrystal prepared by 1.8 MeV proton implantation. The focused proton beam was used to introduce vacancies at a 20 ””m depth layer. Applied doses were in the range of 1.5×1013 to 1.5×1017 ions/cm2. The samples were subsequently annealed in vacuum which resulted in a migration of vacancies and their association with the nitrogen present in the diamond matrix. The proton implantation technique proved versatile to control production of nitrogen-vacancy color centers in thin films.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2013 - Nanoscale sensing and imaging in biology using the nitrogen-vacancy center in diamond [Crossref]
  2. 2018 - Engineering bright fluorescent nitrogen-vacancy (NV) nano-diamonds: Role of low-energy ion-irradiation parameters [Crossref]
  3. 2016 - Quantum Metrology Enhanced by Repetitive Quantum Error Correction [Crossref]
  4. 2020 - Introduction to quantum optimal control for quantum sensing with nitrogen-vacancy centers in diamond [Crossref]
  5. 2009 - Diamonds with a high density of nitrogen-vacancy centers for magnetometry applications [Crossref]
  6. 2018 - Critical Thermalization of a Disordered Dipolar Spin System in Diamond [Crossref]
  7. 2014 - Microwave saturation spectroscopy of nitrogen-vacancy ensembles in diamond [Crossref]
  8. 2019 - Optically detected ferromagnetic resonance in diverse ferromagnets via nitrogen vacancy centers in diamond [Crossref]
  9. 2010 - Broadband magnetometry by infrared-absorption detection of nitrogen-vacancy ensembles in diamond [Crossref]

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