Nanoscale electric field imaging with an ambient scanning quantum sensor microscope
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-09-09 |
| Journal | npj Quantum Information |
| Authors | Ziwei Qiu, Assaf Hamo, Uri Vool, Tony Zhou, Amir Yacoby |
| Institutions | Harvard University |
| Citations | 39 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Nanoscale Electric Field Imaging via NV Electrometry
Section titled âTechnical Documentation & Analysis: Nanoscale Electric Field Imaging via NV ElectrometryâThis document analyzes the research demonstrating nanoscale AC and DC electric field imaging using a single Nitrogen-Vacancy (NV) center in a diamond scanning tip. It highlights the material requirements and experimental methodologies, positioning 6CCVDâs advanced MPCVD diamond solutions as the ideal platform for replicating and extending this cutting-edge quantum sensing research.
Executive Summary
Section titled âExecutive SummaryâThe research successfully demonstrates high-sensitivity nanoscale electric field imaging under ambient conditions using a single NV center in a diamond scanning probe. This work is critical for advancing multimodal quantum sensing platforms.
- High Sensitivity Achieved: Demonstrated AC E-field sensitivity of 26 mV ”m-1 Hz-1/2 and DC E-field gradient sensitivity of 2 V ”m-2 Hz-1/2, representing significant improvements over prior work.
- Nanoscale Resolution: Achieved sub-100 nm spatial resolution, limited primarily by the NV-sample distance (typically <100 nm).
- Screening Overcome: Quantified a strong low-frequency electric field screening effect (RC time constant ~30 ”s, fc = 35.4 kHz) likely caused by mobile surface charges.
- Motion-Enabled DC Sensing: Successfully employed a motion-enabled technique, oscillating the diamond probe at ~190 kHz, to convert the static DC gradient signal into a detectable AC signal, thereby bypassing the screening limitation.
- Material Platform: Utilized electronic-grade CVD diamond fabricated into nanopillar scanning tips (~300 nm diameter) with shallow NV centers (~40 nm depth).
- Future Potential: Paves the way for integrated scanning-probe-based multimodal quantum sensing (combining electrometry and magnetometry) for condensed matter physics and biology.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and material descriptions:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| AC E-Field Sensitivity | 26 | mV ”m-1 Hz-1/2 | Achieved under ambient conditions |
| DC E-Field Gradient Sensitivity | 2 | V ”m-2 Hz-1/2 | Achieved using motion-enabled imaging |
| Spatial Resolution | Sub-100 | nm | Limited by NV-sample distance |
| Diamond Probe Dimensions | ~50 x 55 x 125 | ”m | Electronic-grade CVD diamond plate |
| NV Center Depth | ~40 | nm | Shallow NV location at tip apex |
| Nanopillar Tip Diameter | 300 | nm | Used for scanning |
| Transverse E-field Coupling (dâ„) | 0.17 ± 0.03 | MHz ”m V-1 | Measured NV property |
| Zero-Field Splitting (Dgs) | 2.87 | GHz | NV property |
| Magnetic Bias Field (Bâ„) | ~73 | G | Used for ODMR measurements |
| Screening RC Time Constant | ~30 | ”s | Characterizing surface charge mobility |
| Screening Cut-off Frequency (fc) | 35.4 | kHz | Frequency above which screening diminishes |
| Probe Oscillation Frequency | ~190 | kHz | Used for motion-enabled DC sensing |
| AC Input Voltage (Vpp) | 0.96 | V | Used for AC field mapping |
| DC Input Voltage (Vdc) | 16 | V | Used for DC field mapping |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on precise material engineering, advanced quantum control, and integrated scanning probe techniques:
- Diamond Material Selection: Electronic-grade CVD diamond (Element Six) with natural 13C abundance (1.1%) was chosen for its high purity and long coherence time (T2 ~ 1.5 ”s).
- Probe Fabrication: Diamond plates were micro-fabricated into multiple-pillar scanning probes using reactive ion etching (RIE), resulting in tips with a diameter of approximately 300 nm.
- NV Center Creation: Shallow NV centers (specifically 15NV) were positioned at the apex of the sensing pillar, approximately 40 nm deep, to maximize coupling to external fields.
- Integrated Setup: A custom system combined a confocal microscope (532 nm laser excitation, APD readout) with an Atomic Force Microscope (AFM) operating in ambient conditions. The probe was mounted on a quartz tuning fork for FM-AFM control.
- Quantum Control Sequences:
- AC Sensing: Dynamical-decoupling pulse sequences (e.g., XY-4) were employed for lock-in detection at high frequencies (>200 kHz) to extend T2 and overcome low-frequency screening.
- Low-Frequency AC Sensing: Ramsey-based lock-in detection was used below 50 kHz to characterize the frequency dependence of the screening effect.
- Motion-Enabled DC Sensing: To image static DC fields, the probe was mechanically oscillated at a high frequency (~190 kHz). This motion was synchronized with the quantum sensing pulse sequence, converting the local DC field gradient into a T2-limited AC signal.
- Sample Structure: A U-shaped gold structure (150 ± 5 nm thick, 500 nm gap) was fabricated on a quartz substrate to generate well-defined electric fields for mapping.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-purity diamond materials and custom fabrication services required to replicate and advance this NV electrometry research. Our capabilities directly address the critical material and dimensional requirements of scanning quantum sensors.
Applicable Materials for Quantum Sensing
Section titled âApplicable Materials for Quantum SensingâThe success of this research hinges on using high-quality, low-strain diamond with controlled NV properties. 6CCVD recommends the following materials:
| Material Specification | 6CCVD Offering | Relevance to NV Electrometry |
|---|---|---|
| High-Purity Substrates | Optical Grade Single Crystal Diamond (SCD) | Essential for long electron spin coherence times (T2) and minimal internal strain, crucial for high-sensitivity quantum measurements. |
| Custom Doping | Isotopically Pure 12C SCD | Reduces the 13C spin bath noise, potentially extending T2 beyond the 1.5 ”s reported, leading to higher sensitivity. |
| Shallow NV Precursors | Custom Nitrogen Doping (e.g., 15N) | We provide SCD substrates prepared for precise shallow NV creation via implantation and annealing, enabling the required ~40 nm NV depth control. |
| Probe Material | Custom SCD Plates (up to 500 ”m thick) | Supplies the base material for fabricating the micro-scale diamond probes (50 x 55 x 125 ”m dimensions reported). |
Customization Potential & Fabrication Services
Section titled âCustomization Potential & Fabrication ServicesâThe experimental setup required highly specific geometries for both the diamond probe and the sample electrodes. 6CCVD offers comprehensive services to meet these needs:
- Custom Dimensions and Shaping:
- 6CCVD provides custom laser cutting and shaping of SCD plates to match the exact dimensions required for probe attachment and integration with AFM tuning forks.
- We supply SCD plates/wafers up to 125 mm in size, with thicknesses ranging from 0.1 ”m to 500 ”m, allowing for optimization of probe mass and mechanical resonance.
- Surface Engineering:
- The research requires ultra-smooth surfaces for stable AFM operation and minimal charge noise. 6CCVD guarantees Polishing (Ra < 1 nm for SCD), ensuring optimal surface quality for low-noise measurements.
- Metalization Services:
- The experiment utilized a U-shaped gold structure (Au) for generating the electric field. 6CCVD offers in-house custom metalization (including Au, Pt, Pd, Ti, W, Cu) for fabricating on-chip electrodes or functionalizing the diamond probe tip itself (e.g., for conductive AFM modes).
Engineering Support
Section titled âEngineering SupportâThe integration of NV centers into a scanning probe platform involves complex material science challenges, including crystal orientation, strain management, and surface termination.
- Expert Consultation: 6CCVDâs in-house PhD team specializes in MPCVD growth and post-processing. We can assist researchers with:
- Material Selection: Optimizing the SCD grade and isotopic purity for specific coherence time targets.
- Orientation Control: Providing precisely oriented SCD substrates (e.g., [100], [111], or [110]) critical for maximizing the transverse electric field coupling (dâ„) and aligning the NV axis.
- Strain Mitigation: Advising on material handling and processing techniques to minimize internal strain, which affects the NV zero-field splitting (Dgs).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Nitrogen-vacancy (NV) center in diamond is a promising quantum sensor with remarkably versatile sensing capabilities. While scanning NV magnetometry is well-established, NV electrometry has been so far limited to bulk diamonds. Here we demonstrate imaging external alternating (AC) and direct (DC) electric fields with a single NV at the apex of a diamond scanning tip under ambient conditions. A strong electric field screening effect is observed at low frequencies. We quantitatively measure its frequency dependence and overcome this screening by mechanically oscillating the tip for imaging DC fields. Our scanning NV electrometry achieved an AC E-field sensitivity of 26 mV ÎŒm â1 Hz â1/2 , a DC E-field gradient sensitivity of 2 V ÎŒm â2 Hz â1/2 , and sub-100 nm resolution limited by the NV-sample distance. Our work represents an important step toward building a scanning-probe-based multimodal quantum sensing platform.