Construction and operation of a tabletop system for nanoscale magnetometry with single nitrogen-vacancy centers in diamond

At a Glance

Metadata	Details
Publication Date	2020-02-01
Journal	AIP Advances
Authors	Daiki Misonou, Kento Sasaki, Shuntaro Ishizu, Yasuaki Monnai, Kohei M. Itoh
Institutions	RIKEN Center for Emergent Matter Science, Keio University
Citations	28
Analysis	Full AI Review Included

Technical Analysis and Quantum Material Solutions for Nanoscale Magnetometry

This document analyzes the requirements and achievements detailed in the research paper “Construction and operation of a tabletop system for nanoscale magnetometry with single nitrogen-vacancy centers in diamond” and connects them directly to the advanced MPCVD diamond solutions offered by 6CCVD (6ccvd.com).

Executive Summary

The research successfully demonstrates a compact, reproducible tabletop system for state-of-the-art quantum sensing using single Nitrogen-Vacancy (NV) centers in diamond.

Core Achievement: Design and operation of a single-NV-resolving nanoscale magnetometry system built primarily from commercially available components, making advanced quantum sensing accessible.
Material Foundation: System performance relies critically on high-quality, CVD-grown, (001)-faced, Type-IIa diamond substrates with extremely low native NV defect density (< 5 x 10¹² cm⁻³).
Coherence Metrics: Achieved long coherence times (T₂ = 364 µs) in bulk diamond, significantly exceeding the dephasing time (T₂* = 0.50 µs).
Quantum Sensing Demonstrated: Successful detection and characterization of single ¹³C nuclear spins in bulk diamond using dynamical decoupling (XYk sequences).
Shallow NV Validation: Used proton NMR to determine the depth of near-surface NV centers (d_NV = 6.26 nm), crucial for surface-based sensing applications.
Methodology: Utilizes pulsed Optically Detected Magnetic Resonance (ODMR) protocols, including Rabi oscillation, Ramsey interferometry, Hahn echo, and correlation spectroscopy, controlled by an Arbitrary Waveform Generator (AWG).

Technical Specifications

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

Parameter	Value	Unit	Context
NV Zero-Field Splitting (D)	2.87	GHz	NV electronic spin ground state
NV Gyromagnetic Ratio (γₑ)	28.0	MHz/mT	Used for spin control
DC Magnetic Field (B₀) Range	0 - 30	mT	Achieved via permanent magnet
Excitation Wavelength (λ_ex)	532	nm	Green laser optical pumping
Detection Wavelength (λ_det)	650 - 800	nm	Phonon sideband fluorescence
Single NV Coherence Time (T₂)	364	µs	Hahn Echo measurement (Bulk ¹³C environment)
Single NV Dephasing Time (T₂*)	0.50	µs	Ramsey Interferometry measurement
Shallow NV Depth (d_NV)	6.26	nm	Determined via Proton NMR (Sample #3)
Substrate Orientation	(001)	N/A	CVD-grown Type-IIa
Required NV Density (Bulk)	< 5 x 10¹²	cm⁻³	Necessary for single NV resolution
SPCM Detection Efficiency	> 70	%	At 700 nm

Key Methodologies

The experimental success hinges on precise material preparation and advanced quantum control techniques:

Substrate Selection: Use of high-quality, low-strain, CVD-grown Type-IIa diamond, specified to contain less than 0.03 ppb native NV centers, ensuring a low-noise environment for long T₂.
NV Generation: NV centers were created either in the bulk (as-delivered) or near the surface via ¹⁴N⁺ ion implantation (10 keV, 10¹¹ cm⁻² dose). Ultra-shallow NVs were created using SiO₂ screening layers prior to implantation.
Optical Configuration: A compact confocal scanning microscope setup was constructed using fiber optics and a cage system, achieving a confocal volume < 1 µm³ for single NV resolution.
Microwave Delivery: Broadband planar ring antennas were designed and fabricated to deliver uniform microwave magnetic fields across the sample surface, tuned to the NV resonance frequency (f_res ≈ 2.87 GHz).
Spin Control: Dynamical control of the NV electronic spin was achieved using an Arbitrary Waveform Generator (AWG) to create precise, phase-controlled microwave pulse sequences (e.g., square pulses for π/2 rotations, cosine-square pulses for π rotations, and WURST pulses for robust spin flipping).
Quantum Sensing Protocols: Implementation of advanced multipulse sequences (Carr-Purcell-Meiboom-Gill (CPMG) and XYk sequences) to extend T₂ and perform high-resolution AC magnetometry and correlation spectroscopy for nuclear spin analysis.
Magnetic Field Alignment: DC magnetic fields (B₀) were applied using a cylindrical permanent magnet, manually aligned to one of the four <111> NV symmetry axes (35° tilt relative to the (001) surface).

6CCVD Solutions & Capabilities

The research highlights the critical need for high-purity diamond substrates and precise surface engineering to achieve state-of-the-art quantum sensing. 6CCVD is uniquely positioned to supply and customize the necessary materials to replicate and advance this work.

Research Requirement	6CCVD Applicable Materials & Services	Customization Potential & Value
Applicable Materials	Optical Grade SCD (Single Crystal Diamond): Required for long T₂ coherence times (T₂ = 364 µs achieved in the paper). Our SCD material features ultra-low nitrogen content and high isotopic purity (e.g., ¹²C enrichment) to minimize spin bath noise.	We guarantee Ra < 1 nm polishing on SCD wafers, ensuring minimal surface defects which are critical for shallow NV coherence.
Custom Dimensions	Plates/Wafers up to 125 mm: The paper used small 2 x 2 x 0.5 mm³ samples. 6CCVD provides custom laser cutting and dicing services to produce plates of any required dimension, up to 125 mm (PCD) or large SCD plates, ensuring compatibility with custom antenna or sample stages.	Enables scaling up from tabletop prototypes to larger, integrated quantum devices.
Shallow NV Creation	Custom Ion Implantation & Surface Engineering: The paper demonstrated NVs at 6.26 nm depth. 6CCVD offers precise control over NV depth and density via controlled CVD growth and post-growth ion implantation/annealing, eliminating the need for complex external screening layers.	Critical for maximizing coupling to external analytes (e.g., protons in oil) while maintaining high T₂ coherence.
Microwave Antenna Integration	Metalization Services: The planar ring antennas require precise metal contacts. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) directly onto the diamond surface, streamlining the integration of microwave circuits and electrodes.	Provides ready-to-use diamond components, reducing complexity and fabrication time for researchers.
Substrate Thickness	SCD Thickness Control: The paper used 500 µm thick substrates. 6CCVD offers SCD material ranging from 0.1 µm to 500 µm, allowing researchers to select optimal thickness for thermal management or integration into complex photonic structures (e.g., solid immersion lenses).	Supports advanced device integration beyond simple bulk substrates.

Engineering Support

6CCVD’s in-house PhD team specializes in the physics and material science of NV centers. We offer comprehensive engineering consultation to researchers and engineers working on similar nanoscale magnetometry and quantum sensing projects, assisting with:

Optimizing NV density and depth profiles for specific sensing targets (bulk ¹³C vs. surface protons).
Selecting the appropriate diamond grade (SCD vs. PCD, BDD) based on application requirements (e.g., high T₂ vs. high thermal conductivity).
Designing custom metalization patterns for integrated microwave and electrical components.

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

View Original Abstract

A single nitrogen-vacancy (NV) center in diamond is a prime candidate for a solid-state quantum magnetometer capable of detecting single nuclear spins with prospective application to nuclear magnetic resonance (NMR) at the nanoscale. Nonetheless, an NV magnetometer is still less accessible to many chemists and biologists as its experimental setup and operational principle are starkly different from those of conventional NMR. Here, we design, construct, and operate a compact tabletop-sized system for quantum sensing with a single NV center, built primarily from commercially available optical components and electronics. We show that our setup can implement state-of-the-art quantum sensing protocols that enable the detection of single 13C nuclear spins in diamond and the characterization of their interaction parameters, as well as the detection of a small ensemble of proton nuclear spins on the diamond surface. This article provides extensive discussions on the details of the setup and the experimental procedures, and our system will be reproducible by those who have not worked on the NV centers previously.

Tech Support

Original Source

DOI: https://doi.org/10.1063/1.5128716

References

2017 - Quantum sensing [Crossref]
2008 - Nanoscale magnetic sensing with an individual electronic spin in diamond [Crossref]
2008 - Nanoscale imaging magnetometry with diamond spins under ambient conditions [Crossref]
2014 - Magnetometry with nitrogen-vacancy defects in diamond [Crossref]
2014 - Nitrogen-vacancy centers in diamond: Nanoscale sensors for physics and biology [Crossref]
2018 - Probing condensed matter physics with magnetometry based on nitrogen-vacancy centres in diamond [Crossref]
2018 - Tutorial: Magnetic resonance with nitrogen-vacancy centers in diamond—microwave engineering, materials science, and magnetometry [Crossref]
2013 - Nanoscale nuclear magnetic resonance with a nitrogen-vacancy spin sensor [Crossref]
2013 - Nuclear magnetic resonance spectroscopy on a (5-nanometer)3 sample volume [Crossref]
2014 - Nuclear magnetic resonance spectroscopy with single spin sensitivity [Crossref]