Silicon-vacancy color centers in phosphorus-doped diamond

At a Glance

Metadata	Details
Publication Date	2020-03-09
Journal	Diamond and Related Materials
Authors	Assegid M. Flatae, S. Lagomarsino, Florian Sledz, Navid Soltani, Shannon S. Nicley
Institutions	University of Siegen, Fraunhofer USA
Citations	24
Analysis	Full AI Review Included

Technical Documentation & Analysis: SiV Color Centers in P-Doped Diamond

This document analyzes the research concerning the creation and characterization of Silicon-Vacancy (SiV) color centers in phosphorus-doped (n-type) single-crystal diamond (SCD). This work is highly relevant to 6CCVD’s core mission of supplying high-ppurity MPCVD diamond for quantum technology applications, specifically enabling electrically injected single-photon sources.

Executive Summary

The research successfully demonstrates the creation of single-photon emitters (SPEs) based on SiV centers within n-type, phosphorus-doped diamond, a critical step toward integrated quantum photonics.

First Observation of SPE in P-Doped Diamond: Achieved single-photon emission from SiV centers in P-doped SCD, confirmed by photon anti-bunching with a $g^{2}(0)$ value of 0.3.
Simplified Electrical Integration: The use of n-type diamond allows for simpler electrical excitation schemes, such as Schottky diodes, eliminating the need for complex p-i-n junctions.
Material Purity is Paramount: The primary challenge is suppressing fluorescence background, which is attributed to Nitrogen-Vacancy (NV) centers created during ion implantation and annealing.
Critical Specification: Achieving high spectral quality requires the nitrogen concentration in the CVD growth gases to be extremely low, specifically below 1 ppb.
Methodology: SiV centers were created via shallow Si-ion implantation (depth ≤ 200 nm) into (111) oriented P-doped SCD films, followed by high-vacuum annealing at 1200 °C.
Optimal Performance: Single-photon emission was attained at the lowest tested Si-ion implantation fluence (10⁷ cm⁻²), minimizing defect clustering and background noise.

Technical Specifications

The following table summarizes the critical material and performance parameters extracted from the study.

Parameter	Value	Unit	Context
Host Material	P-doped SCD	N/A	Homoepitaxial growth on HPHT substrates
Substrate Orientation	(111)	N/A	Used for optimal P incorporation
CVD Growth Temperature Range	940 to 1000	°C	Maintained during MWPECVD growth
CVD Pressure Range	140 to 160	Torr	High-pressure growth conditions
Film Thickness Range	1.3 ± 0.2 to 2.2 ± 0.2	µm	Measured by linear encoder
PH₃/CH₄ Ratio Range (Doping)	4300 to 20000	ppm	Used to control P concentration
Required N₂ Purity in Gas	< 1	ppb	Critical for suppressing NV background
Si-ion Implantation Fluence (SPE)	10⁷	cm⁻²	Lowest fluence yielded best single-photon results
Si-ion Implantation Depth	≤ 200	nm	Shallow implantation using Al metal foils
Post-Implantation Annealing	1200	°C	High-vacuum (~ 10⁻⁷ mbar) activation
SiV Zero-Phonon Line (ZPL)	738	nm	Emission peak wavelength
SiV Excited-State Lifetime	0.6 to 1.3	ns	Short lifetime component, ideal for high-speed sources
Single-Photon Purity ($g^{2}(0)$)	0.3	N/A	Confirms anti-bunching signature
Maximum Photon Count Rate	1.576 ± 0.035 x 10³	cps	Measured count rate (background corrected)

Key Methodologies

The successful creation of electrically integrable SiV single-photon sources relies on precise control over CVD growth, implantation, and annealing parameters.

Substrate Selection and Preparation: High-pressure/high-temperature (HPHT) single-crystal diamond substrates with (111) orientation were mechanically polished prior to deposition.
MPCVD Growth: P-doped homoepitaxial diamond films were grown using 2.45 GHz Microwave Plasma-Enhanced CVD (MWPECVD). Phosphine (PH₃) served as the n-type dopant source.
Doping Control: Phosphorus concentration was varied by adjusting the PH₃/CH₄ ratio in the gas feed (4300 ppm to 20000 ppm). Sample B utilized a P-gradient profile.
SiV Creation via Implantation: Si-ions (Si⁺, Si²⁺, Si³⁺) were implanted using a 3 MeV Tandetron accelerator. Aluminum foils were used to reduce ion energy, ensuring shallow implantation (≤ 200 nm).
Defect Activation and Healing: Samples were subjected to high-temperature annealing (1200 °C) in high vacuum (~ 10⁻⁷ mbar) to activate the SiV centers and partially heal lattice damage caused by implantation.
Optical Verification: Single-photon emission was verified using a homemade confocal microscopy setup equipped with a Hanbury-Brown Twiss interferometer to measure the second-order intensity autocorrelation function, $g^{2}(\tau)$.

6CCVD Solutions & Capabilities

This research highlights the critical role of ultra-high purity diamond materials in advancing quantum photonics. 6CCVD is uniquely positioned to supply the necessary specialized materials and fabrication services required to replicate and scale this breakthrough.

Applicable Materials and Purity Control

Research Requirement	6CCVD Material Solution	Technical Specification Match
Ultra-Low Nitrogen Host	Optical Grade Single Crystal Diamond (SCD)	6CCVD specializes in MPCVD growth optimized for extremely low impurity incorporation, meeting the critical < 1 ppb N₂ requirement needed to suppress NV background and achieve high-fidelity SPE.
N-Type Doping	Custom Phosphorus-Doped SCD	We offer precise control over PH₃ doping concentrations, enabling the replication of the 4300 ppm to 20000 ppm gas ratios used in this study for n-type conductivity.
Specific Orientation	(111) Oriented SCD Substrates	While (001) is standard, 6CCVD supplies SCD grown on (111) HPHT substrates, essential for optimizing phosphorus incorporation and replicating the reported device structure.

Customization Potential for Device Integration

The integration of SiV centers into functional quantum devices requires precise material engineering, which 6CCVD provides as a standard service:

Precision Thickness Control: The study utilized thin films (1.3 µm to 2.2 µm). 6CCVD offers SCD films with thicknesses ranging from 0.1 µm up to 500 µm, ensuring optimal material depth for shallow ion implantation (≤ 200 nm).
Advanced Polishing: To minimize surface defects that can compromise implantation yield and optical coupling, 6CCVD provides ultra-smooth polishing services, achieving Ra < 1 nm on SCD wafers.
Custom Dimensions and Scalability: While the paper used small samples (2.6 mm x 2.6 mm), 6CCVD can supply SCD plates up to 10x10 mm and large-area Polycrystalline Diamond (PCD) wafers up to 125 mm for scalable manufacturing efforts.
Metalization Services: For the implementation of electrical injection schemes like Schottky diodes, 6CCVD offers in-house metalization capabilities, including deposition of Au, Pt, Pd, Ti, W, and Cu contacts, streamlining the device fabrication process.

Engineering Support

6CCVD’s in-house PhD team provides expert consultation on material selection and process optimization for quantum applications. We can assist researchers in designing the optimal P-doped SCD host matrix, specifying the required nitrogen purity, and advising on post-processing steps (such as high-temperature annealing at 1200 °C) necessary to maximize the activation yield and spectral quality of SiV centers for electrically injected single-photon sources.

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

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.diamond.2020.107797

References

2010 - Quantum computers [Crossref]
2011 - Advances in quantum metrology [Crossref]
2008 - Cavity-enhanced radiative emission rate in a single photon-emitting diode operating at 0.5 GHz [Crossref]
2013 - A quantum dot single photon source driven by resonant electrical injection [Crossref]
2010 - Electrically driven quantum dot-micropillar single photon source with 34% overall efficiency [Crossref]
2018 - Optical properties of silicon-vacancy color centers in diamond created by ion implantation and post-annealing [Crossref]
2016 - Ultrabright single-photon source on diamond with electrical pumping at room and high temperatures [Crossref]
2015 - Electrical excitation of silicon-vacancy centers in single crystal diamond [Crossref]