Nanoscale electric-field imaging based on a quantum sensor and its charge-state control under ambient condition

At a Glance

Metadata	Details
Publication Date	2021-04-28
Journal	Nature Communications
Authors	Ke Bian, Wentian Zheng, Xianzhe Zeng, Xiakun Chen, Rainer Stöhr
Institutions	University of Stuttgart, Chinese University of Hong Kong
Citations	108
Analysis	Full AI Review Included

Technical Documentation & Analysis: Nanoscale Electric-Field Imaging using Shallow NV Centers

This document analyzes the requirements and achievements detailed in the research paper “Nanoscale electric-field imaging based on a quantum sensor and its charge-state control under ambient condition” and maps them directly to the advanced MPCVD diamond solutions offered by 6CCVD.

Executive Summary

This research successfully demonstrates nanoscale quantitative electric-field imaging and charge-state control using shallow Nitrogen-Vacancy (NV) centers in single-crystal diamond (SCD) under ambient conditions.

Record Spatial Resolution: Achieved a spatial resolution of ~10 nm for electric-field imaging, and a record sub-5 nm (4.6 nm) precision for NV charge-state control.
Methodology: Integrated a qPlus-based Atomic Force Microscope (AFM) with pulsed-Optical Detected Magnetic Resonance (pulsed-ODMR) for high-sensitivity quantum sensing.
Material Requirement: Utilized electronic-grade SCD with ultra-low intrinsic nitrogen concentration (< 5 ppb) to maximize spin coherence time (T₂).
Charge Control Mechanism: Demonstrated highly efficient, stable, and reversible NV charge-state transitions (NV^-, NV⁰, NV⁺) driven by strong local electric fields (up to ~14 MV cm^-1) and photon ionization.
Engineering Foundation: The use of shallow NVs (5-10 nm depth) and super-polished diamond surfaces was critical for achieving high field gradients and close tip proximity (< 1 nm).
Application Potential: This work establishes the foundation for quantitative nanoscale scanning electrometry, enabling the mapping of local charge, electric polarization, and dielectric response in functional materials (e.g., ferroelectrics, ion batteries).

Technical Specifications

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

Parameter	Value	Unit	Context
NV Center Depth	5 - 10	nm	Required for strong coupling to external fields
Intrinsic Nitrogen Concentration	< 5	ppb	Electronic-grade SCD requirement for high T₂
Ion Implantation Energy	5	keV	N¹⁵ ions used for NV creation
Spatial Resolution (Charge Control)	4.6	nm	Highest precision achieved for NV charge switching
Spatial Resolution (Field Imaging)	~10	nm	Achieved using pulsed-ODMR
Minimum Detectable Field Strength	~17.6	kV cm^-1	Based on spectral resolution (~300 kHz)
Maximum Local Electric Field	~14	MV cm^-1	Generated by biased AFM tip
Spin Coherence Time (T₂)	15 - 30	µs	Measured via spin-echo sequence
Spin Contrast	15 - 25	%	Measured via Rabi oscillation
Diamond Membrane Thickness	20 - 30	µm	Final thickness after milling
AFM Tip Oscillation Amplitude	100 - 300	pm	Used to minimize electric noise

Key Methodologies

The experiment relied on precise material engineering and advanced quantum sensing techniques:

Material Selection: Electronic-grade Single Crystal Diamond (SCD) with extremely low intrinsic nitrogen concentration (< 5 ppb) was chosen to maximize spin coherence time (T₂).
Substrate Preparation: SCD chips were milled into thin membranes (20-30 µm thickness) suitable for integration and subsequent processing.
Shallow NV Creation: 5-keV N¹⁵ ion implantation was performed, followed by high-temperature annealing to mobilize vacancies and form near-surface NV centers (5-10 nm depth).
Surface Cleaning: Piranha solution acid boiling was used to reduce surface defects and improve NV coherence/charge stability.
Integration & Sensing Setup: A home-built Scanning Probe Microscope (SPM) integrated with a qPlus-based AFM sensor and a conductive, FIB-sharpened tungsten tip was used for precise tip positioning (< 1 nm proximity).
Quantum Readout: Pulsed-ODMR (using MW π-pulses) was employed to measure the Stark shift of the NV spin levels, providing enhanced sensitivity compared to continuous-wave ODMR.
Charge State Manipulation: Local electric fields, generated by applying high bias voltages (up to ±150 V) to the AFM tip, were combined with 488 nm/532 nm photon ionization to achieve controlled, stable switching between NV^-, NV⁰, and NV⁺ charge states.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-specification diamond materials and customization services required to replicate, extend, and scale this cutting-edge nanoscale electrometry research.

Applicable Materials

To achieve the high coherence times (T₂) and low noise required for quantum sensing, the following 6CCVD materials are recommended:

Electronic Grade SCD Wafers: Our MPCVD Single Crystal Diamond (SCD) is grown with intrinsic nitrogen concentration guaranteed to be < 5 ppb, matching the purity requirements necessary for long-coherence NV centers.
Custom Thinning: We provide SCD plates polished to custom thicknesses ranging from 0.1 µm up to 500 µm, enabling the fabrication of the thin membranes (20-30 µm) required for efficient ion implantation and integration.
Optimized Substrates for Shallow NVs: We offer SCD substrates specifically prepared for subsequent low-energy ion implantation (e.g., 5 keV N¹⁵), ensuring minimal subsurface damage and high yield of high-quality shallow NV centers.

Customization Potential

The integration of the NV sensor requires precise geometry and electrical contacts, areas where 6CCVD provides critical in-house expertise:

Research Requirement	6CCVD Customization Service	Technical Advantage
High-Quality Surface Finish (AFM proximity)	Super-Polishing (Ra < 1 nm): SCD surfaces are polished to an atomic scale (Ra < 1 nm).	Essential for minimizing surface noise, reducing decoherence, and enabling sub-1 nm AFM tip-to-surface distance.
On-Chip Waveguides/Electrodes (Cr/Au)	Custom Metalization: In-house deposition of standard and refractory metals including Au, Pt, Pd, Ti, W, and Cu.	Allows researchers to integrate microwave delivery structures and biasing electrodes directly onto the diamond substrate for pulsed-ODMR experiments.
Custom Dimensions	Large Format & Precision Cutting: SCD plates available up to 125 mm (PCD) and custom laser cutting for precise chip dimensions.	Supports scaling of the experimental setup and integration into complex SPM/AFM systems.

Engineering Support

6CCVD’s in-house team of PhD material scientists specializes in the growth and processing of diamond for quantum applications. We offer comprehensive support for:

Material Selection: Assisting researchers in selecting the optimal SCD grade and orientation for specific implantation energies (e.g., 5 keV N¹⁵) to maximize shallow NV yield and quality.
Process Optimization: Consulting on post-growth treatments, including annealing and surface termination, critical for stabilizing the NV charge state (NV^- vs. NV⁺) and minimizing surface-related decoherence.
Integration Challenges: Providing technical guidance on metalization schemes and bonding techniques necessary for integrating diamond sensors into complex Nanoscale Scanning Electrometry projects.

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

View Original Abstract

Abstract Nitrogen-vacancy (NV) centers in diamond can be used as quantum sensors to image the magnetic field with nanoscale resolution. However, nanoscale electric-field mapping has not been achieved so far because of the relatively weak coupling strength between NV and electric field. Here, using individual shallow NVs, we quantitatively image electric field contours from a sharp tip of a qPlus-based atomic force microscope (AFM), and achieve a spatial resolution of ~10 nm. Through such local electric fields, we demonstrated electric control of NV’s charge state with sub-5 nm precision. This work represents the first step towards nanoscale scanning electrometry based on a single quantum sensor and may open up the possibility of quantitatively mapping local charge, electric polarization, and dielectric response in a broad spectrum of functional materials at nanoscale.

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41467-021-22709-9