High-sensitivity spin-based electrometry with an ensemble of nitrogen-vacancy centers in diamond

At a Glance

Metadata	Details
Publication Date	2017-05-01
Journal	DSpace@MIT (Massachusetts Institute of Technology)
Authors	Philip Hemmer, Edward H. Chen, Hannah Clevenson, Kerry A. Johnson, Linh Pham
Analysis	Full AI Review Included

Technical Analysis and Documentation for Spin-Based Electrometry

Executive Summary

This documentation analyzes a breakthrough research paper demonstrating a high-sensitivity, solid-state electrometer utilizing an ensemble of Nitrogen-Vacancy (NV$^-$) centers in CVD diamond.

Core Achievement: Demonstrated a spin-based, all-dielectric electrometer achieving shot-noise-limited sensitivities approaching 1 (V/cm)/√Hz in the ultra-low frequency regime (0.05-10 Hz).
Mechanism: Detection relies on the electric-field-induced Stark shift on the NV$^-$ ground state, measured via Optically Detected Magnetic Resonance (ODMR).
Noise Mitigation: The method successfully separates temperature-induced noise (D parameter fluctuations) from electric-field fluctuations, allowing for highly stable measurements under ambient conditions.
Material Requirements: The experiment utilized a 3.0 x 3.0 x 0.32 mm³ diamond plate grown via Chemical Vapor Deposition (CVD) with low nitrogen concentration (~1 ppb NV$^-$ density).
Future Potential: Theoretical projections show that utilizing high-density, low-strain SCD material could improve sensitivity to 6 x 10^-3 (V/cm)/√Hz, yielding a 200x performance enhancement over current results.
Application: This technique is critical for miniaturized, highly localized electric field sensing in applications such as microelectronic diagnostics and in vitro biological studies, operating below the optical diffraction limit.
6CCVD Value: 6CCVD specializes in the custom, low-strain Single Crystal Diamond (SCD) material required to replicate this sensitivity and achieve the projected performance gains through controlled doping and precision metalization.

Technical Specifications

Parameter	Value	Unit	Context
Diamond Plate Dimensions	3.0 x 3.0 x 0.32	mm³	Material used for ensemble NV$^-$ detection
Crystallographic Orientation	(100)	Face	Orientation used for electrode evaporation
Initial NV$^-$ Density	~1	ppb	Produced during CVD growth process
Measured Sensitivity (Shot-Noise Limited)	1.0 ± 0.1	(V/cm)/√Hz	NV$^-$ ground state sensitivity
Projected Sensitivity (Optimized Material)	6 x 10^-3	(V/cm)/√Hz	Anticipated maximum sensitivity with high-density NV$^-$
Operating Frequency Range	0.05 - 10	Hz	Demonstrated low-frequency operation
Dynamic Range	20	dB	Measured range of electrometer operation
Incident Laser Power	1.8	W	Power used to achieve maximum sensitivity
Laser Power Density (Saturation)	~30	µW/µm²	High power required to saturate NV$^-$ photoluminescence
Ground State Crystal-Field Splitting (D)	2.8	GHz	Key parameter used for ODMR temperature compensation
Ground State Transverse Field Sensitivity (d_⊥)	17	Hz/(V/cm)	Required material characteristic for Stark shift sensing

Key Methodologies

The experiment utilized a comprehensive MPCVD diamond synthesis and integration workflow, demonstrating capabilities in both material control and high-speed readout.

Material Growth and Preparation:
- CVD diamond plate (3.0 x 3.0 x 0.32 mm³) with (100) faces was synthesized, achieving a low NV$^-$ concentration (~1 ppb).
Electrode Fabrication:
- Gold (Au) electrodes were custom-evaporated onto the two parallel (100) faces of the diamond plate to apply the necessary electric fields ($E$).
Optical Excitation and Readout:
- A continuous-wave (CW) laser beam (~200 µm diameter) was focused through the edge of the diamond plate to excite the NV$^-$ ensemble.
- Photoluminescence (PL) was collected by a lens setup and detected by a Silicon detector.
Microwave (MW) Delivery:
- MW excitation was applied locally via an $\Omega$-shaped stripline patterned on a printed circuit board (PCB), allowing for ODMR measurements.
Detection System Integration:
- A custom, home-built digital lock-in amplifier (LIA) system, utilizing a high-speed Field-Programmable Gate Array (FPGA) and Digital-to-Analog Converter (DAC), performed both waveform generation and signal readout.
Noise Compensation:
- Electric-field fluctuations were distinguished from thermal fluctuations by simultaneously monitoring two strain/electric-field sensitive transitions (m$_{s}$ = ±0). The difference of these time traces isolated the electric-field signal, while the sum revealed the temperature fluctuations (due to the D parameter shift).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced diamond material and fabrication services required to replicate this high-sensitivity electrometer and achieve the predicted 200x performance increase.

Applicable Materials & Optimization

To replicate and extend this research, 6CCVD recommends providing Optical Grade Single Crystal Diamond (SCD) engineered specifically for quantum sensing applications.

High Purity, Controlled Doping: To achieve the projected sensitivity of 6 x 10^-3 (V/cm)/√Hz, researchers require SCD with a significantly higher density of NV$^-$ centers (up to 1000x denser than the 1 ppb material used). 6CCVD offers controlled nitrogen doping during the MPCVD growth process (or post-processing irradiation/annealing optimization) to achieve high, uniform NV ensemble densities (ppm range).
Low Strain Requirement: High-sensitivity electrometry relies on long inhomogeneous coherence times ($T_{2}^{}$). Our Low-Strain MPCVD SCD material minimizes crystal defects and internal strain ($\Pi$), directly supporting longer $T_{2}^{}$ coherence and maximizing electrometer performance according to the shot-noise sensitivity equation (Eq. 4).
Orientation: We routinely supply SCD wafers with precise (100) or (111) crystallographic orientations, ensuring optimal alignment for electrode deposition and electric field application relative to the NV axis.

Customization Potential for Replication & Scaling

Requirement from Paper	6CCVD Custom Capability	Engineering Advantage
Custom Dimensions (3 x 3 x 0.32 mm³)	We provide plates/wafers in custom dimensions, replicating the exact size used or scaling up to 125 mm (PCD). SCD plates are available up to 500 µm thickness.	Enables rapid prototyping and scaling to production volumes for compact sensor arrays.
Metalization Layers (Au Electrodes)	Full In-House Metalization Suite: We offer custom thin-film deposition including Au, Pt, Ti, Pd, W, and Cu. We can deposit the necessary Ti/Au or Ti/Pt/Au schemes for robust ohmic contact electrodes.	Eliminates the need for external cleanroom access, ensuring high-quality, repeatable electrode integration onto the diamond surface.
Surface Finish	Precision Polishing: SCD is polished to roughness Ra < 1nm, critical for optimal optical coupling efficiency and reducing scattering losses.	Enhances photon collection rate ($\Gamma$), which is a critical factor in achieving projected shot-noise limited sensitivity (Eq. 4).
Deep Etching/Structuring	Available internal laser cutting and deep reactive ion etching (DRIE) for creating waveguides or resonant structures.	Allows for future integration of optical patterning needed to increase photon collection efficiency (up to 100x improvement cited in the paper).

Engineering Support

6CCVD’s in-house PhD material science team can assist researchers and technical engineers in optimizing the diamond recipe for similar Spin-Based Quantum Sensing projects. We offer consultation on:

Selecting the ideal nitrogen concentration (ppb vs. ppm) to balance NV density and coherence properties ($T_{2}^{*}$).
Specifying the appropriate crystal orientation for maximal transverse electric susceptibility ($k_{\perp}$).
Designing robust metalization layouts compatible with high-power MW excitation and low-frequency DC bias voltage application.

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

View Original Abstract

We demonstrate a spin-based, all-dielectric electrometer based on an ensemble of nitrogen-vacancy (NV[superscript −]) defects in diamond. An applied electric field causes energy-level shifts symmetrically away from the NV[superscript −]‘s degenerate triplet states via the Stark effect; this symmetry provides immunity to temperature fluctuations allowing for shot-noise-limited detection. Using an ensemble of NV[superscript −]s, we demonstrate shot-noise-limited sensitivities approaching 1 (V/cm)/√Hz under ambient conditions, at low frequencies (<10 Hz), and over a large dynamic range (20 dB). A theoretical model for the ensemble of NV[superscript −]s fits well with measurements of the ground-state electric susceptibility parameter 〈k[subscript ⊥]〉. Implications of spin-based, dielectric sensors for micron-scale electric-field sensing are discussed.

Tech Support

Original Source

DOI: None