Statistically modeling optical linewidths of nitrogen vacancy centers in microstructures

At a Glance

Metadata	Details
Publication Date	2020-08-27
Journal	Physical review. B./Physical review. B
Authors	Mark Kasperczyk, Josh A. Zuber, Arne Barfuss, Johannes Kölbl, Viktoria Yurgens
Institutions	University of Basel
Citations	17
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Quantum NV Center Engineering

Research Paper Analyzed: Statistically Modeling Optical Linewidths of Nitrogen Vacancy Centers in Microstructures (Kasperczyk et al., 2020)

Executive Summary

This research successfully investigates the critical relationship between nitrogen implantation techniques and the optical linewidth of Nitrogen Vacancy (NV) centers, essential for advancing solid-state quantum technologies.

Application Focus: Optimization of NV center Zero-Phonon Line (ZPL) linewidths for high-coherence quantum computing, entanglement protocols, and photonic cavity coupling.
Core Challenge: Achieving spectrally stable, narrow linewidths (< 500 MHz) in highly structured diamond (membranes and cantilevers) while controlling the source of nitrogen (native vs. implanted).
Methodology: Implementation of a novel “post-implantation” technique, where ¹⁴N and ¹⁵N ions are implanted after all nano-structuring is complete, followed by multi-stage high-temperature annealing (up to 1200 °C).
Key Finding (Native N): NV centers formed from native nitrogen impurities in the high-purity diamond exhibit the narrowest linewidths (median ~100 MHz).
Key Finding (Implanted N): Post-implantation successfully yielded narrow ¹⁵NV centers (< 500 MHz), demonstrating that implanted nitrogen can be used to create high-quality NV centers in thin structures (down to 0.87 µm).
Material Requirement: Ultra-low nitrogen and boron Single Crystal Diamond (SCD) is essential to minimize native NV background and allow precise control over implanted NV creation.

Technical Specifications

The following hard data points were extracted from the research paper, detailing the material properties and process parameters required for high-quality NV center creation in structured diamond.

Parameter	Value	Unit	Context
Starting Material Purity (N)	< 5	ppb	Electronic Grade Diamond
Starting Material Purity (B)	< 1	ppb	Electronic Grade Diamond
Structured Thickness (Membrane)	2.5 - 5	µm	Nonuniform thickness
Structured Thickness (Cantilever)	2.5 - 4	µm	Variable dimensions
Thinnest Structured Area Tested	0.87	µm	Sample C, post-implanted ¹⁵N
Implantation Energy (Sample A/B)	12	keV	¹⁴N or ¹⁵N ions
Implantation Energy (Sample C)	52	keV	¹⁵N ions
Implantation Angle	7	°	Relative to sample mount
Implantation Fluence (Sample A/B)	10¹¹	ions/cm²	High fluence test
Implantation Fluence (Sample C)	5 x 10⁹	ions/cm²	Low fluence test
Annealing Stage 1	4	hours @ 400 °C	Initial low-temp anneal
Annealing Stage 2	10	hours @ 800 °C	Intermediate anneal
Annealing Stage 3	2	hours @ 1200 °C	High-temperature vacancy migration
Transform Limited Linewidth	≈ 13	MHz	Theoretical limit for NV center
Achieved Narrowest Linewidth	< 250	MHz	Observed in 1.57 µm thick structured area (Sample C)
Median Linewidth (Native ¹⁴NV)	≈ 100	MHz	Narrow population in Sample B

Key Methodologies

The experiment relied on precise material fabrication, isotopic implantation, and rigorous thermal processing to control NV center formation and spectral properties.

Material Selection and Structuring: Electronic grade SCD diamond (N < 5 ppb, B < 1 ppb) was used. Samples were fabricated into thin membranes (2.5-5 µm) and cantilevers (2.5-4 µm) using established etching procedures.
Post-Implantation: Nitrogen ions (either ¹⁴N or ¹⁵N isotopes) were implanted after all nano-structuring was completed. This “post-implantation” approach aims to minimize fabrication-induced strain and damage near the NV centers.
- Parameters: Implantation energies ranged from 12 keV to 52 keV, with fluences from 5 x 10⁹ to 10¹¹ ions/cm².
Multi-Stage Annealing: Samples underwent a three-stage annealing process to mobilize vacancies and form the NV centers: 4 hours at 400 °C, 10 hours at 800 °C, and 2 hours at 1200 °C.
Surface Cleaning: A tri-acid clean was performed post-annealing to remove surface contamination.
Characterization: Photoluminescence Excitation (PLE) spectroscopy was used to measure optical linewidths, and pulsed Optically Detected Magnetic Resonance (ODMR) was used to isotopically classify the NV centers (¹⁴N vs. ¹⁵N).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-purity materials and custom fabrication services necessary to replicate, extend, and industrialize the findings of this research, particularly in the critical area of post-implantation NV engineering.

Applicable Materials for Quantum NV Engineering

The success of this research hinges on starting with ultra-pure diamond to control the nitrogen source. 6CCVD offers the necessary material grades:

Optical Grade Single Crystal Diamond (SCD): Required for achieving the narrowest possible ZPL linewidths (median ≈ 100 MHz). Our SCD is grown via MPCVD, ensuring extremely low native nitrogen (< 1 ppb available upon request) and minimal strain, which is crucial for spectral stability.
Custom Isotopic Doping: For extending the research into controlled NV creation, 6CCVD offers custom doping during growth, including precise incorporation of ¹⁵N or other dopants (e.g., Silicon, Germanium) for alternative color centers.

Customization Potential for Structured Devices

The paper utilizes thin membranes (down to 0.87 µm) and cantilevers, requiring precise material control and post-processing support.

Research Requirement	6CCVD Capability	Value Proposition
Thin Membranes (0.87 µm - 5 µm)	SCD Thickness Control: We supply SCD plates polished down to 0.1 µm thickness. Substrates up to 10 mm thick are available for bulk studies.	Enables direct replication of thin structured samples and exploration of ultra-thin device geometries.
High-Quality Surface Finish	Polishing: SCD surfaces are polished to Ra < 1 nm, minimizing surface charge noise and reducing inhomogeneous broadening.	Essential for maintaining the narrow linewidths achieved through post-implantation and annealing.
Integration with Photonic Cavities	Custom Metalization: We offer in-house deposition of Au, Pt, Pd, Ti, W, and Cu.	Supports the integration of NV centers into microwave circuits or photonic structures (e.g., Ti/Pt/Au contacts for ODMR).
Custom Dimensions	Large Format & Cutting: Plates/wafers up to 125 mm (PCD) and custom laser cutting services for SCD.	Provides large-area material for high-throughput fabrication of structured arrays (cantilevers, membranes).

Engineering Support & Consultation

The statistical model developed in this paper highlights the need for rigorous comparison between different fabrication recipes (implantation energy, annealing profile, structure thickness).

Recipe Optimization: 6CCVD’s in-house PhD team specializes in MPCVD growth parameters and material science. We offer consultation to assist researchers in selecting the optimal starting material (purity, orientation, thickness) to match specific NV creation recipes (e.g., optimizing material for 52 keV ¹⁵N implantation).
Global Logistics: We provide reliable global shipping (DDU default, DDP available) to ensure sensitive materials reach your research facility safely and promptly.

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

View Original Abstract

We investigate the effects of a novel approach to diamond nanofabrication and nitrogen vacancy (NV) center formation on the optical linewidth of the NV zero-phonon line (ZPL). In this post-implantation method, nitrogen is implanted after all fabrication processes have been completed. We examine three post-implanted samples, one implanted with $^{14}$N and two with $^{15}$N isotopes. We perform photoluminescence excitation (PLE) spectroscopy to assess optical linewidths and optically detected magnetic resonance (ODMR) measurements to isotopically classify the NV centers. From this, we find that NV centers formed from nitrogen naturally occuring in the diamond lattice are characterized by a linewidth distribution peaked at an optical linewidth nearly two orders of magnitude smaller than the distribution characterizing most of the NV centers formed from implanted nitrogen. Surprisingly, we also observe a number of $^{15}$NV centers with narrow ($<500,\mathrm{MHz}$) linewidths, implying that implanted nitrogen can yield NV centers with narrow optical linewidths. We further use a Bayesian approach to statistically model the linewidth distributions, to accurately quantify the uncertainty of fit parameters in our model, and to predict future linewidths within a particular sample. Our model is designed to aid comparisons between samples and research groups, in order to determine the best methods of achieving narrow NV linewidths in structured samples.

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevb.102.075312