Decay rate enhancement of diamond NV-centers on diamond thin films
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-06-24 |
| Journal | Optics Express |
| Authors | Hao Li, JunâYu Ou, V.A. Fedotov, Nikitas Papasimakis |
| Institutions | University of Southampton |
| Analysis | Full AI Review Included |
Decay Rate Enhancement of Diamond NV-Centers on Diamond Thin Films: Technical Analysis
Section titled âDecay Rate Enhancement of Diamond NV-Centers on Diamond Thin Films: Technical AnalysisâExecutive Summary
Section titled âExecutive Summaryâ- Core Achievement: Experimental demonstration of a two-fold enhancement in the decay rate (lifetime shortening) of neutral nitrogen-vacancy (NV0) centers.
- Mechanism: The enhancement is achieved by depositing nanodiamond clusters onto a thin diamond film (200 nm) supported by a silicon substrate, rather than bare silicon.
- Quantified Lifetime Reduction: The average NV0 lifetime was substantially shortened from 30 ns (on bare Si) to 17 ns (on the diamond thin film).
- Physical Origin: The decay rate increase is attributed to the strong coupling of the NV emitters to Fabry-Perot slab modes supported by the thin film, alongside the presence of non-radiative decay channels (loss in the underlying Si).
- Tunability: Numerical modeling confirms that the radiative decay rate can be efficiently controlled and tuned by up to 90% by varying the thickness of the supporting diamond film.
- Methodology: Time-Resolved Cathodoluminescence (TR-CL) was used for experimental measurement, complemented by full-wave 3D electromagnetic modeling.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Experimental Average Lifetime (Bare Si) | 30 | ns | Mean (Ό) lifetime for NV0 clusters |
| Experimental Average Lifetime (Diamond Film) | 17 | ns | Mean (Ό) lifetime on 200 nm film |
| Lifetime Distribution Standard Deviation (Bare Si) | 6 | ns | Broad distribution (Ï) |
| Lifetime Distribution Standard Deviation (Diamond Film) | 4 | ns | Narrower distribution (Ï) |
| Diamond Film Thickness (Experimental) | 200 | nm | Thickness of the thin film on Si |
| Nanodiamond Size | ~120 | nm | Diameter of deposited nanodiamonds |
| Estimated NV Centers per Particle | ~103 | N/A | Concentration within nanodiamonds |
| Zero Phonon Line (ZPL) Wavelength | 575 | nm | Wavelength selected for NV0 emission study |
| Radiative Decay Rate Tuning Depth | Up to 90 | % | Achievable tuning range via film thickness |
| Simulated Lifetime (Bare Si) | 91.49 | ns | Single dipole model (Tsim) |
| Simulated Lifetime (Diamond Film) | 81.73 | ns | Single dipole model (Tsim) on 200 nm film |
| Refractive Index (Diamond) | 2.40 | N/A | Used in modeling (at 575 nm) |
| Refractive Index (Silicon) | 4.00 + 0.03i | N/A | Used in modeling (at 575 nm) |
| Electron Beam Current (TR-CL) | ~1.8 | nA | Maintained during measurement |
Key Methodologies
Section titled âKey MethodologiesâThe study combined material preparation, advanced spectroscopy, and computational modeling:
-
Sample Preparation:
- Nanodiamonds (~120 nm) were dispersed in methanol using a 10-minute ultrasonic bath.
- The solution was deposited via drop casting onto two substrates: a bare 500 ”m Si wafer and a 200 nm thick diamond film on a 500 ”m Si wafer.
-
Time-Resolved Cathodoluminescence (TR-CL) Setup:
- A Scanning Electron Microscope (SEM) was operated in fixed-spot mode (10 kV LaB6 source).
- A pulsed electron beam was generated using a beam blanker synchronized by a wave function generator.
- Emitted light was collected by a parabolic mirror, collimated, and directed to a VIS/NIR spectrometer (Horiba iHR320).
-
Measurement and Data Acquisition:
- Time-correlated single-photon counting (TCSPC) was used to measure decay traces.
- Photons were spectrally filtered to select the NV0 ZPL emission (575 nm ± 1.8 nm).
- 60 nanodiamond clusters were measured on each substrate type, covering sizes from 120 nm to 1500 nm.
-
Lifetime Analysis:
- The TR-CL traces were fitted using a bi-exponential function. The slower component (Ï2) was identified as the NV0 center lifetime.
- Statistical distributions of lifetimes were characterized by the average (ÎŒ) and standard deviation (Ï).
-
Electromagnetic Modeling:
- Full-wave 3D simulations (COMSOL 5.3a) modeled a single NV0 dipole embedded in a nanodiamond sphere (60 nm radius) on the substrate.
- The modeling calculated the total decay rate (ÎłTot), distinguishing between radiative (ÎłRad) and non-radiative (ÎłNon) decay rates, confirming the role of non-radiative loss in the underlying Si.
- The dependence of ÎłRad on film thickness was fitted to a sine function, confirming coupling to Fabry-Perot modes (period TFPdiamond â 120 nm).
Commercial Applications
Section titled âCommercial ApplicationsâThis research directly supports the development of high-performance quantum devices and integrated photonics based on diamond NV centers:
- High-Speed Quantum Emitters: The enhanced decay rate (Purcell effect) allows for faster photon emission, which is critical for creating efficient, high-repetition-rate single-photon sources necessary for quantum communication and cryptography.
- Integrated Quantum Photonics: The ability to tune the radiative decay rate by controlling the thin film thickness provides a simple, scalable method for optimizing the coupling of NV centers to on-chip photonic structures (e.g., waveguides, resonators).
- Advanced Quantum Sensing: Shorter lifetimes enable faster readout and initialization of NV spin states, improving the bandwidth and temporal resolution of diamond-based sensors for magnetic fields, electric fields, and temperature.
- Engineered Diamond Substrates: This work drives the need for high-quality, precisely controlled thin diamond films (potentially grown via CVD) optimized for specific quantum applications, where film thickness dictates emitter performance.
- Local Density of States (LDOS) Mapping: The sensitivity of the NV decay rate to the local dielectric environment reinforces its utility as a nanoscale probe for characterizing complex photonic structures and materials.
View Original Abstract
We demonstrate experimentally two-fold enhancement of the decay rate of NV° centers on diamond/Si substrate as opposed to a bare Si substrate. We link the decay enhancement to the interplay between the excitation of substrate modes and the presence of non-radiative decay channels. We show that the radiative decay rate can vary by up to 90% depending on the thickness of the diamond film.