Engineering the collapse of lifetime distribution of nitrogen-vacancy centers in nanodiamonds

At a Glance

Metadata	Details
Publication Date	2021-06-28
Journal	Applied Physics Letters
Authors	H. Li, J.Y. Ou, B. Gholipour, J.K. So, D. Piccinotti
Institutions	Nanyang Technological University, University of Southampton
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Engineering the Collapse of Lifetime Distribution of Nitrogen-Vacancy Centers in Nanodiamonds

This document analyzes the research demonstrating active control over Nitrogen-Vacancy (NV) center emission statistics using chalcogenide thin films, and outlines how 6CCVD’s advanced MPCVD diamond materials can accelerate and scale this quantum technology.

Executive Summary

Core Achievement: Experimental demonstration of a dramatic collapse in the lifetime distribution of NV centers in nanodiamonds (NDs) by embedding them in thin chalcogenide (SbTe) films.
Quantified Improvement: The lifetime distribution spread was narrowed by over five times, reducing from >7 ns (reference sample) to approximately 1 ns (embedded sample).
Lifetime Shortening: The average NV$^0$ lifetime was successfully shortened by a factor of two, converging to 11 ns across various dielectric environments.
Underlying Mechanism: The narrowing is enforced by substantially increased non-radiative decay, which dominates relaxation and renders the total decay rate ($\gamma_{tot}$) insensitive to the random orientation of the NV center’s electric dipole moment.
Material Control: The optical response of the host chalcogenide film can be continuously tuned (from strongly plasmonic to strongly dielectric) via stoichiometric engineering, offering a straightforward path to active control over emission statistics.
Application Potential: This method provides a scalable solution for creating highly uniform, stable single-photon sources, critical for integrated optical quantum platforms in sensing, communication, and computing.

Technical Specifications

The following hard data points were extracted from the research paper, focusing on material properties and performance metrics.

Parameter	Value	Unit	Context
ND Average Size	120	nm	Nanodiamonds used (Sigma Aldrich)
NV$^0$ Centers per ND	~1200	Centers	Neutral nitrogen-vacancy centers
NV$^0$ Zero Phonon Line (ZPL)	575	nm	Wavelength used for characterization
Reference Average Lifetime	Nearing 20	ns	NDs placed on SbTe film
Embedded Average Lifetime	11	ns	NDs embedded in SbTe film
Lifetime Distribution Spread (Reference)	>7	ns	NDs placed on SbTe film
Lifetime Distribution Spread (Embedded)	~1	ns	Achieved in Strong/Weak Plasmonic (SPL/WPL) areas
SbTe Film Thickness Range ($d$)	40 to 100	nm	Overall thickness after two deposition rounds
SbTe Real Permittivity (Re $\epsilon$)	-23 to 13	N/A	Tuned continuously across samples at 575 nm
SbTe Imaginary Permittivity (Im $\epsilon$)	15 to 30	N/A	High loss component across all compositions
Non-Radiative Decay Enhancement (Parallel Dipole, SDL)	>18	Times higher	ND embedded vs. ND on SbTe
Non-Radiative/Radiative Ratio (Parallel Dipole, SDL)	Approaching 174	N/A	Maximum ratio for embedded NDs

Key Methodologies

The experiment combined high-precision material synthesis with advanced optical characterization techniques.

Substrate and Deposition: A 28 mm x 28 mm Silicon (Si) substrate was used. Thin SbTe films (thickness $d/2$, 20 to 50 nm) were deposited using a high-throughput Physical Vapor Deposition (PVD) system.
PVD Conditions: Deposition occurred under high vacuum ($\le 10^{-8}$ mbar) at room temperature, utilizing off-axis Knudsen cell sources and fixed wedge shutters to create independent density gradients of high-purity Sb and Te ($\ge 99.9999$ %).
ND Integration: Nanodiamonds (120 nm average size) were dispersed in methanol via ultrasonic bath and drop-cast onto the first SbTe film.
Embedding Layer: A second SbTe film (thickness $d/2$) was deposited over the ND layer using the same PVD procedure, resulting in an overall embedded film thickness $d$ ranging from 40 nm to 100 nm.
Optical Characterization: Complex permittivity ($\epsilon$) of the SbTe films was mapped across the sample using variable angle spectroscopic ellipsometry at the NV$^0$ zero phonon line wavelength (575 nm).
Lifetime Measurement: Time-Resolved Cathodoluminescence (TR-CL) was performed using a Scanning Electron Microscope (SEM) operating at 10 kV with pulsed electron beam modulation for time-correlated single-photon counting.
Data Extraction: Lifetimes of NV$^0$ centers were extracted by fitting the time-correlated histograms with a bi-exponential function.

6CCVD Solutions & Capabilities

This research validates a critical step toward realizing scalable, integrated quantum platforms based on diamond NV centers. 6CCVD provides the foundational MPCVD diamond materials and engineering services required to transition this research from proof-of-concept to robust, integrated devices.

Applicable Materials for Quantum Platforms

The high-quality nanodiamonds used in this study are typically derived from high-purity single crystal diamond (SCD). For integrated quantum devices, the substrate itself must offer superior optical and thermal management.

Research Requirement	6CCVD Material Recommendation	Technical Rationale
High-Purity NV Source	Optical Grade Single Crystal Diamond (SCD)	Provides the lowest strain and highest purity material necessary for creating stable, high-coherence NV centers, whether used as bulk substrates or processed into high-quality NDs.
Integrated Sensing/Computing	Electronic Grade Polycrystalline Diamond (PCD)	For large-area integration (up to 125mm), PCD offers superior thermal conductivity and mechanical stability compared to Si, crucial for managing heat dissipation in active chalcogenide films.
Active Electrical Tuning	Boron-Doped Diamond (BDD) Substrates	BDD acts as a conductive electrode platform, enabling direct electrical control over the phase-change chalcogenide film (SbTe) for dynamic tuning of the NV decay rates.

Customization Potential

The integration of thin films and nanostructures requires precise control over substrate dimensions, surface quality, and electrode placement. 6CCVD’s in-house capabilities directly address these needs:

Custom Dimensions: We supply SCD plates and PCD wafers in custom dimensions up to 125mm diameter, supporting the scale-up of integrated quantum devices beyond the 28 mm x 28 mm Si substrate used in the paper.
Thickness Control: We offer precise thickness control for SCD (0.1µm to 500µm) and robust diamond substrates up to 10mm thick, providing flexibility for various optical coupling and thermal management schemes.
Ultra-Low Roughness Polishing: Achieving uniform thin-film deposition (like the 40-100 nm SbTe film) is critical. 6CCVD guarantees surface roughness of Ra < 1nm for SCD and Ra < 5nm for inch-size PCD, minimizing surface-induced non-radiative losses.
Custom Metalization: The conclusion suggests active control via electrical or thermal switching. We offer internal metalization services (Au, Pt, Pd, Ti, W, Cu) for integrating electrodes directly onto the diamond substrate, facilitating electrical tuning of the chalcogenide phase.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth and post-processing of diamond for quantum and electronic applications. We provide expert consultation on:

Material Selection: Assisting researchers in selecting the optimal diamond grade (SCD vs. PCD, doping level, orientation) to maximize NV center stability and coherence for similar Integrated Quantum Photonic projects.
NV Creation: Advising on nitrogen incorporation strategies during growth or post-growth implantation/annealing to optimize NV concentration and charge state.
Integration Challenges: Providing technical support for bonding, thin-film deposition, and laser cutting to ensure successful integration of complex material stacks like the ND/chalcogenide system onto diamond platforms.

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

View Original Abstract

We demonstrate experimentally that the distribution of the decay rates of nitrogen-vacancy centers in diamond becomes narrower by over five times for nanodiamonds embedded in thin chalcogenide films.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0054780

References

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2013 - Spatially resolved quantum nano-optics of single photons using an electron microscope [Crossref]