Determining the position of a single spin relative to a metallic nanowire

At a Glance

Metadata	Details
Publication Date	2021-04-08
Journal	Journal of Applied Physics
Authors	J. F. Da Silva Barbosa, M. Lee, P. Campagne-Ibarcq, P. Jamonneau, Y. Kubo
Institutions	Université Paris-Sud, Pohang University of Science and Technology
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Single Spin Localization in MPCVD Diamond

This document analyzes the research paper “Determining the position of a single spin relative to a metallic nanowire” (arXiv:2011.09968v1) to highlight the critical role of high-purity MPCVD diamond and to propose specific material solutions available through 6ccvd.com.

Executive Summary

This research successfully demonstrates the precise nanoscale localization of individual Nitrogen Vacancy (NV) centers relative to a metallic nanowire, a crucial step for developing hybrid quantum devices with strong spin-microwave coupling.

Core Achievement: Determined the relative position of individual NV centers in diamond with approximately 10 nm accuracy using single-NV vector magnetometry.
Material Foundation: The experiment relied on commercial electronic-grade, chemical-vapor-deposition (CVD) grown diamond, confirming the suitability of 6CCVD’s high-purity Single Crystal Diamond (SCD) substrates for advanced quantum engineering.
Critical Fabrication: Achieved shallow NV implantation (11 ± 5 nm depth) using ¹⁵N²⁺ ions, requiring ultra-low surface roughness and high material purity to minimize decoherence.
Hybrid Integration: Successfully integrated a metallic nanowire (5 nm Ti / 15 nm Al stack) on the diamond surface via electron-beam lithography and lift-off, demonstrating robust material compatibility.
Quantum Metric: Measurements directly yielded the spin-microwave coupling constant ($g/2\pi$) in the range of 0.6 to 1 kHz, validating the platform for future circuit-QED architectures.
6CCVD Value Proposition: 6CCVD provides the necessary high-quality SCD substrates, custom metalization, and ultra-precise polishing (Ra < 1 nm) required to replicate and scale this critical quantum technology.

Technical Specifications

The following hard data points were extracted from the research paper, detailing the physical and quantum parameters achieved:

Parameter	Value	Unit	Context
NV Positioning Accuracy	~10	nm	Relative to the nanowire
Implantation Ion	¹⁵N²⁺	N/A	Used for creating NV centers
Implantation Energy	7.5	keV	Nitrogen ion beam energy
Implantation Depth (SRIM)	11 ± 5	nm	Expected depth of shallow NVs
Annealing Temperature	900	°C	Vacuum anneal for 1 hour
Nanowire Thickness	20	nm	Total thickness (5 nm Ti / 15 nm Al)
Nanowire Width (Typical)	40	nm	Defined by EBL
Nanowire Length	500	nm	Defined by EBL
Zero-Field Splitting (D/2π)	2.87	GHz	NV electron spin ground state
Spin-Microwave Coupling ($g/2\pi$)	0.6 to 1	kHz	Measured for the three NVs
Effective Gyromagnetic Ratio ($\gamma_{\perp, \perp}/2\pi$)	75	MHz/T	Perpendicular component

Key Methodologies

The fabrication of the hybrid quantum device involved precise material preparation and nanoscale patterning:

Substrate Preparation: Started with commercial electronic-grade, CVD-grown diamond.
Alignment Mark Patterning: Alignment marks were patterned via electron-beam lithography (EBL) and etched into the diamond surface.
Implantation Mask Fabrication: A resist mask (120 nm thick PMMA) was patterned using EBL to create an array of holes (~20 nm diameter) for selective implantation.
Ion Implantation: The sample was implanted with a beam of ¹⁵N²⁺ nitrogen ions at 7.5 keV, targeting a flux of ~2500 N/µm².
Thermal Annealing: The sample was annealed at 900 °C for 1 hour in vacuum to mobilize vacancies and form NV centers.
Surface Cleaning: Multi-step cleaning process including boiling acid mixture (HNO₃:H₂SO₄:HClO₄), Piranha clean (H₂SO₄ and H₂O₂), and oxygen plasma treatment.
Nanowire Fabrication: Aluminum electrodes and nanowires were fabricated using EBL, followed by three-angle evaporation and lift-off. The metal stack was 5 nm Titanium (Ti) followed by 15 nm Aluminum (Al).
Characterization: Optically-Detected Magnetic Resonance (ODMR) using a 532 nm laser was performed to identify ¹⁵NV centers and measure the magnetic field components generated by DC current through the nanowire.

6CCVD Solutions & Capabilities

The success of this research hinges on the quality and preparation of the diamond substrate, areas where 6CCVD offers industry-leading expertise and customization.

Applicable Materials

To replicate or extend this research, the highest quality diamond is essential for maintaining long NV center coherence times ($\gamma_2$).

6CCVD Material Recommendation	Specification & Relevance to Research
Optical Grade SCD (Single Crystal Diamond)	Required for low-strain, high-purity quantum applications. Our SCD features extremely low native nitrogen concentration (< 1 ppb), minimizing background defects and maximizing NV center yield control.
Electronic Grade SCD Substrates	Provides the necessary crystal quality and low defect density for reliable shallow implantation (7.5 keV targeting 11 nm depth).
Custom Thickness SCD	Available in thicknesses from 0.1 µm up to 500 µm, allowing researchers to select the optimal bulk material for thermal management or integration into complex photonic structures.

Customization Potential

The paper utilized specific dimensions, metal stacks, and surface preparation that align perfectly with 6CCVD’s custom fabrication services:

Ultra-Low Roughness Polishing: The shallow implantation and high-resolution EBL patterning (40 nm nanowire width) demand an exceptionally smooth surface. 6CCVD guarantees Ra < 1 nm for SCD, ensuring optimal lithography fidelity and minimal surface-induced decoherence.
Custom Metalization Stacks: The paper used a Ti/Al stack (5 nm Ti / 15 nm Al). 6CCVD offers in-house deposition of critical metals, including Ti, Al, Pt, Au, Pd, W, and Cu, allowing researchers to specify adhesion layers (Ti) and conductive layers (Al) precisely.
Large-Area Substrates: While the paper used small chips, 6CCVD can supply PCD wafers up to 125 mm in diameter and large-area SCD, enabling the scaling of NV array fabrication for industrial or large-scale quantum network prototypes.
Precision Dicing and Shaping: 6CCVD provides custom laser cutting and dicing services to match specific chip dimensions required for integration into microwave circuits and cryostats.

Engineering Support

The precise control over NV center depth and position is critical for maximizing the spin-microwave coupling constant ($g$). 6CCVD’s in-house PhD team specializes in material science and quantum defect engineering.

Material Selection for Quantum Projects: We assist clients in selecting the optimal SCD purity and orientation (e.g., [111] vs. [100]) to maximize NV center performance for similar single-spin magnetometry and circuit-QED projects.
Surface Termination Consultation: We provide guidance on optimal surface cleaning and termination protocols (e.g., oxygen plasma, acid cleaning) necessary to achieve the low surface noise required for shallow NV centers, minimizing charge instability issues noted in the paper.
Global Logistics: 6CCVD ensures reliable, global shipping (DDU default, DDP available) of sensitive diamond substrates, supporting international collaborations like those detailed in this research.

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

View Original Abstract

The nanoscale localization of individual paramagnetic defects near an electrical circuit is an important step for realizing hybrid quantum devices with strong spin-microwave photon coupling. Here, we fabricate an array of individual nitrogen vacancy (NV) centers in diamond near a metallic nanowire deposited on top of the substrate. We determine the relative position of each NV center with ∼10 nm accuracy, using it as a vector magnetometer to measure the field generated by passing a DC through the wire.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0042987