All‐Optical Electric Field Sensing with Nanodiamond‐Doped Polymer Thin Films
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-07-24 |
| Journal | Advanced Functional Materials |
| Authors | R.C. Styles, Mengke Han, Toon Goris, J. G. Partridge, Brett C. Johnson |
| Institutions | The University of Adelaide, The University of Melbourne |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”- Core Achievement: Demonstration of all-optical electric field sensing using hydrogenated Fluorescent Nanodiamonds (FNDs) embedded in a solid-state polymer capacitor device.
- Sensing Mechanism: Electric field-induced modulation of the Nitrogen-Vacancy (NV) center charge state (transient conversion of NV0 to NV-) read out via Photoluminescence (PL) intensity changes.
- Performance Metrics: The device operates across an electric field range up to 625 kV cm-1 (at 100 V applied voltage).
- High Sensitivity: The estimated electric field sensitivity for a single NV center is 72 V cm-1 Hz-1/2, representing an order of magnitude improvement over ODMR-based sensing in bulk diamond.
- Fast Dynamics: The NV- PL signal shows a strong transient increase (up to 31%) within 0.1 ms of voltage application, demonstrating rapid charge state modulation.
- Proposed Model: The transient PL change is attributed to an electric field-driven redistribution and trapping of photoexcited electrons originating from substitutional nitrogen defects (Ns0) into nearby NV centers.
- Reliability: Over 95% of FNDs integrated into the capacitor showed the characteristic transient PL increase upon external voltage application.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| FND Particle Size | 100 | nm | Hydrogen surface termination |
| Maximum Electric Field (E) | 625 | kV cm-1 | Achieved at 100 V applied voltage |
| Single FND Sensitivity | 19 | V cm-1 Hz-1/2 | Assuming shot noise-limited detection |
| Single NV Sensitivity | 72 | V cm-1 Hz-1/2 | Estimated for an optimized optical system |
| Transient Response Time | < 0.1 | ms | Time for NV- PL increase after voltage application |
| Maximum NV- PL Increase | 31 | % | Transient peak amplitude observed in >95% of FNDs |
| NV- ZPL Wavelength | 637 | nm | Zero-Phonon Line (ZPL) |
| NV0 ZPL Wavelength | 575 | nm | Zero-Phonon Line (ZPL) |
| Total Device Capacitance (Measured) | 0.416 | nF | Measured at ~67 Hz operational frequency |
| Leakage Current (at 20 V) | 39 | nA | Corresponds to 513 MΩ resistance |
| ITO Substrate Resistance | 30 - 60 | Ω cm2 | Commercial indium-tin-oxide coated glass |
| Laser Excitation Wavelength | 532 | nm | Continuous-Wave (CW) |
| Maximum Excitation Power (Pex) | 900 | µW | Used for studying PL dynamics |
Key Methodologies
Section titled “Key Methodologies”The device is a multilayer capacitor fabricated on an ITO-coated glass substrate, designed to embed FNDs in a solid-state dielectric matrix.
- Substrate Preparation: Commercial Indium-Tin-Oxide (ITO) coated glass (18 x 18 mm) was used as the transparent conductive electrode.
- Bottom Dielectric Layer (POD): A 250 nm thick layer of polyoctadiene (POD) was deposited onto the ITO via plasma polymerization using 1-7 octadiene precursor gas (10-4 mbar pressure, 50 W power).
- FND-Doped Layer (PVP):
- 100 nm hydrogenated FNDs (1 mg mL-1 in water) were sonicated and dispersed in a Polyvinylpyrrolidone (PVP, MW 40,000) solution (5% wt/vol in 1-propanol).
- The final FND concentration was 0.25 mg mL-1.
- 100 µl of the solution was spin-coated onto the POD layer at 1800 RPM (2000 RPM/s acceleration), yielding a ~400 nm thick FND-doped PVP film.
- Top Dielectric and Electrode: A second 250 nm POD layer was deposited, followed by the sputtering of a 50 nm thick Chromium/Gold (Cr/Au) electrode.
- Voltage Application: Square voltage pulses (Von = +100 V, Voff = 0 V) were applied between the ITO and gold electrodes using a function generator and amplifier, creating the local electric field.
- Optical Measurement: A custom confocal PL setup was used:
- Excitation: 532 nm laser focused through the ITO layer via a 100x objective (NA = 0.90).
- Detection: PL collected through the same objective. NV- PL was isolated using 700 nm long-pass and 900 nm short-pass filters. NV0 PL was isolated using 550 nm long-pass and 650 nm short-pass filters.
- Acquisition: Photons counted with an avalanche photodiode (APD) with a time resolution of 0.1 ms.
Commercial Applications
Section titled “Commercial Applications”This technology is highly relevant for solid-state, integrated sensing platforms, offering advantages over traditional microwave-based NV sensing by eliminating the need for complex MW circuitry.
- Integrated Circuit (IC) Diagnostics: Nanoscale, non-invasive, all-optical voltage and electric field mapping within active semiconductor devices and integrated circuits, crucial for failure analysis and performance optimization.
- Quantum Computing Hardware: Monitoring local electric fields and charge noise in solid-state quantum systems (e.g., silicon carbide, silicon qubits) where NV centers can be integrated as internal, non-perturbing sensors.
- Solid-State Bio-Interfaces: Sensing electric potentials and charge dynamics at the interface between biological systems and solid-state devices, particularly where water or conductive media attenuate MW signals.
- Miniaturized Sensors (SWaP): Development of highly integrated, low Size, Weight, and Power (SWaP) electric field sensors for portable or drone-mounted applications, leveraging the all-optical readout.
- Ratiometric Sensing Platforms: Utilizing the simultaneous, opposite changes in NV- and NV0 PL intensity for robust, ratiometric voltage detection that is intrinsically immune to laser power fluctuations.
View Original Abstract
Abstract The nitrogen‐vacancy (NV) center is a photoluminescent defect in diamond that exists in different charge states, NV ‐ and NV 0 , that are sensitive to the NV’s nanoscale environment. Here, all‐optical voltage sensing with NV centers in fluorescent nanodiamonds (FNDs) is demonstrated in a solid‐state device based on electric field‐induced NV charge state modulation. More than 95% of FNDs integrated into a polymer‐based capacitor device show a transient increase in NV − PL intensity up to 31% within 0.1 ms after application of an external voltage, accompanied by a simultaneous decrease in NV 0 PL. The NV − PL signal increases with increasing electric field from 0 to 619 kV cm −1 . The best electric field sensitivity for a single FND is 18 V cm −1 Hz −½ . The NV charge state photodynamics are investigated on the millisecond timescale. The change in NV PL is found to strongly depend on the rate of photoexcitation. A model is proposed that qualitatively explains the results based on an electric field‐induced redistribution of photoexcited electrons from substitutional nitrogen to NV centers, leading to a transient conversion of NV 0 to NV − centers. These results contribute to the development of FNDs as reliable, all‐optical, nanoscale electric field sensors in solid‐state systems.