Nanomechanical Sensing Using Spins in Diamond

At a Glance

Metadata	Details
Publication Date	2017-02-01
Journal	Nano Letters
Authors	M. S. J. Barson, Phani Peddibhotla, Preeti Ovartchaiyapong, Kumaravelu Ganesan, Richard Taylor
Institutions	The University of Melbourne, Universität Ulm
Citations	139
Analysis	Full AI Review Included

Nanomechanical Sensing Using Spins in Diamond: Technical Documentation & Solutions

Executive Summary

This research introduces Nano-Spin-Mechanical Sensors (NSMS), unifying high-sensitivity Nanomechanical Systems (NEMS) with quantum nanosensing based on the Nitrogen-Vacancy (NV) center in diamond. This breakthrough leverages the extreme mechanical and quantum properties of Single Crystal Diamond (SCD) to achieve unprecedented nanoscale analytical power.

Technology Unification: NSMS exploit the mechanical susceptibility of the NV center’s electron spin to detect local stress and strain, combining nanomechanical sensing with quantum metrology.
Core Achievement: Complete characterization of the NV center’s spin-mechanical interaction parameters (a₁, a₂, b, and c), essential for robust NSMS device design.
Proof-of-Principle: Successful demonstration of force measurement using NV centers embedded in SCD microcantilevers, confirming the validity of the spin-mechanical model with an average force uncertainty of $\approx$29 nN.
Predicted Force Sensitivity: Optimized diamond nanopillars (w=0.1 µm, h=1 µm) are predicted to achieve a DC force sensitivity of 100 pN Hz^-1/2, enabling unparalleled AC force imaging in cellular biomechanics.
Mass Spectrometry Potential: NSMS constructed from diamond nanobeams are projected to achieve mass resolution equivalent to 50 carbon atoms within 1 second of measurement time, allowing single-macromolecule inertial imaging.
Material Necessity: The success of NSMS relies exclusively on high-purity, high-coherence Single Crystal Diamond (SCD) substrates, ideal for precision nanostructure fabrication.

Technical Specifications

The following parameters were determined via Optically Detected Magnetic Resonance (ODMR) spectroscopy on Type Ib diamond samples or calculated based on validated Euler-Bernoulli mechanical models.

Parameter	Value	Unit	Context
Zero-Field Splitting (D)	$\approx$2.87	GHz	NV center ground state spin-spin interaction
Young’s Modulus (E)	1220	GPa	Elastic property of diamond used in beam theory
T₂* Coherence Time (Max)	$\approx$200	µs	Spin coherence time for Ramsey sequence
T₂ Coherence Time (Max)	$\approx$3	ms	Spin coherence time for Hahn-echo sequence
Stress Susceptibility (a₁)	4.86(2)	MHz/ GPa	Determined under hydrostatic pressure
Stress Susceptibility (a₂)	-3.7(2)	MHz/ GPa	Determined under uniaxial stress
Stress Susceptibility (b)	-2.3(3)	MHz/ GPa	Determined under uniaxial stress
Stress Susceptibility (c)	3.5(3)	MHz/ GPa	Determined under uniaxial stress
Measured Force Uncertainty ($\Delta$F_ODMR)	$\approx$29	nN	Microcantilever experiment (12 min integration)
Predicted DC Force Sensitivity ($\eta_{DC}$)	100	pN Hz^-1/2	Optimal nanopillar (w=0.1 µm, h=1 µm)
Predicted Mass Sensitivity ($\eta_{mass}$)	$\approx$1	zg Hz^-1/2	Optimal nanobeam (0.1x0.1x5 µm)
Mass Resolution (Equivalent)	50	Carbon Atoms	Achievable within $\approx$1 s of measurement time
Nanopillar Array Spatial Resolution (s)	$\geq$250	nm	Minimum spacing required for wide-field ODMR
AC Sensing Frequency Band	10 kHz $\leftrightarrow$ 100 MHz		Constrained by microwave pulse length ($\approx$10 ns)

Key Methodologies

The experimental approach focused on characterizing the spin-mechanical interaction in bulk diamond and validating the force sensing principle using fabricated microcantilevers.

Spin-Mechanical Characterization: Uniaxial stress experiments were conducted using 2x2x2 mm³ cuboid Type Ib diamonds featuring {100}, {110}, and {111} faces.
Stress Generation: Homogeneous uniaxial stresses were generated by applying pressure to opposing sample faces using a pneumatic piston-steel anvil setup.
ODMR Spectroscopy: Optically Detected Magnetic Resonance (ODMR) was utilized to measure the induced shifts ($\delta$) and splittings ($\Delta$) in the NV center spin resonances as a function of applied pressure ($\sigma_p$).
Microcantilever Fabrication: Single NV centers were embedded in diamond microcantilevers (SCD nanostructures).
Force Application: Forces were applied to the microcantilever tips using a motorized tungsten tip assembly (Figure 2c).
Comparative Force Measurement: Applied force was determined independently by two methods:
- Mechanical Fit ($F_{E-B}$): Optical measurements of cantilever bending profiles, fit using Euler-Bernoulli beam theory.
- Spin Sensing ($F_{ODMR}$): ODMR measurements coupled with the newly characterized spin-mechanical interaction parameters and the known dimensions/orientation of the cantilever.
Nanostructure Modeling: Theoretical limits and operating principles for NSMS were established using canonical geometries (cylindrical nanopillars and nanobeams) based on the characterized stress susceptibility parameters.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced Single Crystal Diamond (SCD) materials and custom engineering required to replicate and scale this pioneering NSMS technology for quantum metrology, biological imaging, and mass spectrometry applications.

Material Recommendations for NSMS Engineering

The foundational requirement for achieving the predicted high sensitivities (100 pN force, 50-carbon atom mass resolution) is the use of diamond with extremely long spin coherence times ($T_2$). This necessitates ultra-high purity material.

NSMS Application Requirement	6CCVD Applicable Material	Technical Advantage
Required Material Purity	Optical Grade Single Crystal Diamond (SCD)	Ultra-low concentration of intrinsic defects (low nitrogen) ensures maximum spin coherence (long T₂/T₂*) crucial for quantum sensing limits.
High-Volume Fabrication	SCD Substrates up to 125mm Diameter	Provides industry-leading wafer sizes necessary for the scale-up and multiplexing of nanopillar sensor arrays (Figure 3b).
Nanobeam/Cantilever Structures	SCD Thicknesses 0.1 µm - 500 µm	Allows researchers to select the precise thickness required for optimizing resonant frequencies, Q-factors, and overall mechanical sensitivity for mass spectrometry (e.g., the 0.1x0.1x5 µm nanobeam model).
Uniaxial Stress Characterization	Custom Cut SCD Cuboids/Plates	We provide Type IIa or customized Type Ib (for higher initial NV concentration) samples cut to specific dimensions and crystallographic orientations (e.g., {100}, {110}, {111}) for mechanical susceptibility testing.

Customization Potential for NSMS

The development of NSMS requires sub-micron fabrication techniques and the integration of microwave control circuits. 6CCVD’s specialized engineering services directly support these complex device architectures.

Precision Substrate Preparation: The fabrication of high-aspect-ratio nanostructures (nanopillars and nanobeams) requires substrates with exceptional surface quality. 6CCVD guarantees Ra $\lt$ 1nm polishing on SCD, minimizing etching complexity and improving the mechanical integrity of the final structures.
Integrated Microwave Control: The paper highlights the necessity of microwave wires to perform ODMR and Hahn-echo sequences (Figure 1c, 3b). 6CCVD offers extensive custom metalization services including deposition and patterning of Au, Pt, Pd, Ti, W, and Cu layers, enabling on-chip microwave delivery lines adjacent to the NSMS structures.
Targeted NV Placement: While NV creation is post-processing (e.g., implantation/irradiation), 6CCVD’s engineering team can consult on optimal SCD specifications, including specific nitrogen incorporation methods (Type Ib or delta-doping layers), to ensure NV centers are positioned precisely where maximum bending stress occurs ($\xi_x = 0$ or $l$ and $\xi_z = \pm h/2$).

Engineering Support & Logistics

6CCVD provides technical partnership to accelerate research in diamond quantum sensing:

Engineering Consultation: Our in-house PhD team provides expert guidance on material selection and crystallographic orientation specific to maximizing NV spin-mechanical coupling for similar Quantum Nanometrology projects.
Global Supply Chain: We ensure reliable delivery of sensitive, high-value diamond materials worldwide, with DDU (Delivered Duty Unpaid) as default and DDP (Delivered Duty Paid) options available.

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

View Original Abstract

Nanomechanical sensors and quantum nanosensors are two rapidly developing technologies that have diverse interdisciplinary applications in biological and chemical analysis and microscopy. For example, nanomechanical sensors based upon nanoelectromechanical systems (NEMS) have demonstrated chip-scale mass spectrometry capable of detecting single macromolecules, such as proteins. Quantum nanosensors based upon electron spins of negatively charged nitrogen-vacancy (NV) centers in diamond have demonstrated diverse modes of nanometrology, including single molecule magnetic resonance spectroscopy. Here, we report the first step toward combining these two complementary technologies in the form of diamond nanomechanical structures containing NV centers. We establish the principles for nanomechanical sensing using such nanospin-mechanical sensors (NSMS) and assess their potential for mass spectrometry and force microscopy. We predict that NSMS are able to provide unprecedented AC force images of cellular biomechanics and to not only detect the mass of a single macromolecule but also image its distribution. When combined with the other nanometrology modes of the NV center, NSMS potentially offer unparalleled analytical power at the nanoscale.

Tech Support

Original Source

DOI: https://doi.org/10.1021/acs.nanolett.6b04544