Blue Delayed Luminescence Emission in Neutral Nitrogen Vacancy Containing Chemical Vapor Deposition Synthetic Diamond

At a Glance

Metadata	Details
Publication Date	2024-03-13
Journal	physica status solidi (a)
Authors	Ff ion L. L. James, Amber M. Wassell, Colin D. McGuinness, Peter M. P. Lanigan, David Fisher
Institutions	Cardiff University
Analysis	Full AI Review Included

Technical Documentation & Analysis: Blue Delayed Luminescence in N-V CVD Diamond

Executive Summary

This document analyzes the research on delayed luminescence in nitrogen-doped CVD diamond, focusing on the discovery of a novel blue emission center.

Novel Discovery: First recorded observation of long-lived delayed blue luminescence (centered at ≈465 nm) in N-doped CVD diamond, distinct from the known NV⁰ center emission (575 nm).
Temperature Dependence: The blue emission dominates the delayed photoluminescence (PL) spectra at cryogenic temperatures (below 190 K), while the NV⁰ emission is most prominent at 290 K.
Excitation Method: Sample excited above the diamond bandgap using pulsed short-wave UV radiation (190-227 nm) with a 2.9 µs pulse duration.
Defect Physics Implication: The data suggests the existence of a previously undocumented “blue center” and a proposed “trap state,” indicating complex multi-exponential decay pathways.
Material Relevance: The study utilized an untreated CVD diamond (0.13 ppm N), highlighting the critical role of controlled nitrogen doping in synthetic diamond research.
Application Potential: This research provides essential optical signatures for advanced gemological screening (distinguishing synthetic vs. natural diamond) and fundamental defect engineering.

Technical Specifications

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

Parameter	Value	Unit	Context
Diamond Type Analyzed	CVD (N-doped)	N/A	Untreated, Round brilliant cut
Nitrogen Impurity Level	0.13	ppm	Determined via UV absorption techniques
Sample Weight	0.4	Ct	Color Grade L, Clarity VS1
Excitation Wavelength Range	190-227	nm	Pulsed short-wave UV radiation
Excitation Pulse Duration	2.9	µs	Full-width half maximum (FWHM)
Measurement Temperature Range	77-350	K	Range for PL and decay measurements
Delayed PL Measurement Delay	90	µs	Time delay after initial excitation pulse
Blue Emission Center Wavelength	≈465	nm	Broadband delayed luminescence peak
Sharp Blue Peaks Observed	419, 455, 499	nm	Observed atop the broadband feature below 190 K
NV⁰ Zero-Phonon Line (ZPL)	575	nm	Characteristic neutral nitrogen-vacancy defect
Longest Average Decay Lifetime (455 nm)	0.26	s	Observed at 77 K
Shortest Average Decay Lifetime (455 nm)	0.14	s	Observed at 190 K

Key Methodologies

The experiment relied on precise time-gated and temperature-dependent optical spectroscopy:

Sample Preparation: An untreated nitrogen-doped CVD diamond was characterized for nitrogen concentration (0.13 ppm) using UV absorption.
Excitation System: A Hamamatsu Photonics L7685 xenon flash lamp, spectrally filtered by a bespoke band-pass filter, provided pulsed UV excitation (190-227 nm, 2.9 µs duration).
Temperature Control: Prompt and delayed photoluminescence spectra were measured as a function of temperature in the range 77 K to 350 K.
Prompt PL Acquisition: Spectral data was recorded concurrently with the initial excitation pulse, compensating for electrical latency via an 8 µs offset.
Delayed PL Acquisition: Spectral data was recorded 90 µs after the initial excitation, integrated over a 30 ms gate, and accumulated over 20 images to capture long-lived emission.
Time-Gated Imaging: Visual color shifts of the emission were captured at fixed delays (0 µs, 90 µs, 70 ms) across three temperatures (77 K, 150 K, 296 K).
Time-Resolved Decay Analysis: Decay curves at 455 nm and 575 nm were fitted using multi-exponential models (3 or 4 exponentials) to calculate average decay lifetimes (τ).

6CCVD Solutions & Capabilities

6CCVD provides the high-quality MPCVD diamond materials and customization services necessary to replicate, extend, and commercialize the findings related to delayed luminescence and defect engineering.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage
Material Replication & Control	Nitrogen-Doped Single Crystal Diamond (SCD): We offer SCD with precise, controlled nitrogen doping to match or systematically vary the 0.13 ppm concentration used in the study.	Enables researchers to isolate the novel “blue center” by controlling the NV⁰ defect density and ensuring ultra-low background impurity levels.
High-Purity Optical Substrates	Optical Grade SCD: Available in thicknesses from 0.1 µm up to 500 µm, with ultra-low strain and high transmission in the UV range (190-227 nm).	Minimizes scattering and absorption losses during short-wave UV excitation, crucial for maximizing the signal-to-noise ratio in delayed PL measurements.
Large-Area Integration	Custom Dimensions (PCD & SCD): We supply Polycrystalline Diamond (PCD) plates up to 125 mm in diameter and large-area SCD substrates (up to 10 mm thick).	Facilitates integration into complex optical setups, such as large-scale cryogenic systems or advanced gemological screening instruments.
Surface Quality for Optical Studies	Precision Polishing: SCD surfaces polished to Ra < 1 nm; Inch-size PCD polished to Ra < 5 nm.	Ensures superior surface quality necessary for minimizing artifacts and maximizing light collection efficiency in time-gated imaging and spectroscopy.
Probing Trap States (Future Work)	Boron-Doped Diamond (BDD): We offer both BDD SCD and BDD PCD materials.	Essential for future research investigating the proposed trap state (Figure 6) by systematically modifying the charge state of defects via p-type doping.
Advanced Device Fabrication	Custom Metalization Services: In-house deposition of Au, Pt, Pd, Ti, W, and Cu.	Supports the creation of integrated thermal contacts or electrodes required for precise temperature control and potential electrical injection studies referenced in the paper.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD growth parameters, defect engineering, and advanced characterization techniques. We offer expert consultation on material selection and doping profiles required to replicate or extend this research on Delayed Luminescence and Defect Physics projects. Our expertise ensures the material delivered meets the stringent requirements for cryogenic and time-resolved optical studies.

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

View Original Abstract

Herein, the authors investigate the temperature‐dependent properties of delayed luminescence in an as‐grown nitrogen‐containing chemical vapor deposition synthetic diamond gemstone when excited above its bandgap. At room temperature, this gemstone exhibits delayed luminescence from nitrogen‐vacancy centers at 575 nm. However, at 77 K, the first recorded instance of a long‐lived delayed blue luminescence centered at ≈465 nm, accompanied by spectral peaks at 419, 455, and 499 nm is reported. By analyzing spectral and temporal data at different temperatures, it can be speculated on potential photophysical transitions. This discovery documents the initial observation of this delayed luminescence emission, contributing to the collective understanding of synthetic diamonds.

Tech Support

Original Source

DOI: https://doi.org/10.1002/pssa.202300651