Phase transition observation of nanoscale water on diamond surface

At a Glance

Metadata	Details
Publication Date	2022-01-01
Journal	Acta Physica Sinica
Authors	Zhiping Yang, Xi Kong, Fazhan Shi, Jiangfeng Du
Citations	2
Analysis	Full AI Review Included

Technical Documentation: Nanoscale Water Phase Transition Sensing via NV-Diamond

This document analyzes the research paper “Phase transition observation of nanoscale water on diamond surface” (Acta Physica Sinica, 71, 067601, 2022). The study successfully utilizes shallow Nitrogen-Vacancy (NV) centers in MPCVD diamond to perform nanoscale Nuclear Magnetic Resonance (NMR) and simultaneous temperature sensing, observing the solid-liquid phase transition of water confined to the diamond surface.

Executive Summary

Breakthrough Sensing: Demonstrated simultaneous, non-invasive measurement of nanoscale NMR signals and local temperature using a single NV center in diamond.
Application: Successful observation of the solid-liquid phase transition of water confined to the diamond surface, showing a phase change temperature higher than bulk water (0 °C).
Material Requirement: Requires high-quality, ultra-shallow NV centers (6-7 nm depth) fabricated in a thin, highly polished Single Crystal Diamond (SCD) substrate.
Dual Functionality: The NV center acts as both a nano-NMR sensor (distinguishing liquid vs. solid phase via linewidth/decay time) and a highly sensitive thermometer (via Zero-Field Splitting, D).
Key Finding: Liquid water exhibited a narrow NMR linewidth (53 kHz) and fast correlation decay (12 µs), while solid ice showed a narrower linewidth (33 kHz) and significantly longer decay time (46 µs), confirming the change in molecular dynamics.
Temperature Sensitivity: The NV center demonstrated a temperature sensitivity of dD/dT = -87(12) kHz/K, enabling precise local thermal monitoring.

Technical Specifications

The following hard data points were extracted from the experimental results and material preparation sections of the paper:

Parameter	Value	Unit	Context
Diamond Substrate Dimensions	2 x 2 x 0.05	mm	Thin film SCD used for sensing.
Diamond Thickness	50	µm	Required for integration with the waveguide/cooler setup.
Ion Implantation Species	¹⁴N⁺	N/A	Source for creating NV centers.
Ion Implantation Energy	5	keV	Used to control NV depth.
NV Center Average Depth	6-7	nm	Ultra-shallow depth critical for surface sensing.
Annealing Temperature	800	°C	Post-implantation thermal treatment (in vacuum).
NV Zero-Field Splitting (D)	2870.26	MHz	Measured at room temperature (19 °C).
NV Zero-Field Splitting (D)	2871.53	MHz	Measured at liquid phase (11.1 °C).
Temperature Sensitivity (dD/dT)	-87(12)	kHz/K	NV center used as a local thermometer.
Liquid Water NMR Linewidth	53(9)	kHz	Measured at 11.1 °C.
Solid Ice NMR Linewidth	33(5)	kHz	Measured at -8.8 °C.
Liquid Water Correlation Decay Time	12(3)	µs	Fast decay due to molecular diffusion out of the detection volume.
Solid Ice Correlation Decay Time	46(11)	µs	Slow decay due to fixed molecular positions (dipole interaction limited).

Key Methodologies

The experiment relied on precise material engineering and advanced quantum control sequences:

Material Selection: Use of a thin (50 µm) Single Crystal Diamond (SCD) film grown via MPCVD.
NV Creation: Nitrogen-Vacancy centers were created via low-energy ¹⁴N⁺ ion implantation (5 keV) to achieve an ultra-shallow depth (6-7 nm).
Defect Activation: Samples were annealed at 800 °C in vacuum to mobilize vacancies and form NV centers.
Surface Functionalization: The diamond surface was treated with a strong acid mixture (H₂SO₄, HNO₃, HClO₄) and Piranha solution (H₂SO₄, H₂O₂) to achieve a hydrophilic, hydroxyl-terminated surface, promoting water adsorption.
Experimental Setup: The diamond was placed on a coplanar waveguide and coupled to a semiconductor cooler, allowing temperature control down to -10 °C in a nitrogen atmosphere.
Quantum Measurement: Optically Detected Magnetic Resonance (ODMR) was used to measure the NV electronic spin state.
Nano-NMR: Periodic Dynamic Decoupling (DD) pulse sequences were applied to the NV electron spin to detect the weak magnetic signals from the water proton nuclear spins.
Temperature Sensing: The NV center’s Zero-Field Splitting (D) was measured via ODMR and correlated with temperature (D-T calibration) to provide highly localized thermal monitoring.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and customization services required to replicate, extend, and commercialize this nanoscale quantum sensing research.

Applicable Materials

To achieve the high coherence and ultra-shallow NV depth necessary for surface sensing, the following 6CCVD material is required:

6CCVD Material	Specification Match	Relevance to Research
High Purity SCD	Low native nitrogen content (< 1 ppb)	Essential for maximizing NV coherence time (T₂) and minimizing background noise.
Optical Grade SCD	Ra < 1 nm polishing	Ultra-low surface roughness is critical for precise, shallow ion implantation (6-7 nm) and stable surface chemistry (hydroxyl termination).
Custom Thin SCD Plates	0.1 µm - 500 µm thickness	6CCVD can supply the exact 50 µm thickness used, or thinner films for enhanced thermal management or integration.

Customization Potential

The success of this experiment hinges on precise material dimensions and surface preparation, all of which are standard offerings at 6CCVD:

Custom Dimensions: The paper used 2 mm x 2 mm samples. 6CCVD offers custom laser cutting and fabrication of plates/wafers up to 125 mm in size, allowing for scaling or integration into larger quantum devices.
Shallow NV Layer: While the paper used 5 keV ¹⁴N⁺ implantation, 6CCVD works closely with leading ion implantation facilities to ensure the precise depth and concentration of NV centers (e.g., 6-7 nm depth) required for optimal surface sensitivity.
Surface Termination: The research required a hydrophilic (hydroxyl-terminated) surface. 6CCVD provides custom surface preparation services, including advanced cleaning and termination (e.g., Oxygen, Hydrogen, or Hydroxyl termination) to match specific experimental requirements.
Metalization Integration: Although the metalization (Copper/Waveguide) was external, 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for direct integration onto the diamond surface, simplifying device fabrication for future quantum sensors.

Engineering Support

This research demonstrates the power of NV-based nano-NMR for studying complex interfacial dynamics. 6CCVD’s in-house team of PhD material scientists and quantum engineers can assist researchers in extending this work:

Material Selection for Confined Systems: We provide consultation on selecting the optimal SCD grade, thickness, and crystallographic orientation for similar projects involving nanoscale confined systems (e.g., biological interfaces, microfluidics, or chemical reaction monitoring).
Boron Doping for Electrochemistry: For researchers looking to extend this work to electrochemical sensing (e.g., water splitting or catalysis), 6CCVD offers Boron-Doped Diamond (BDD) films, which provide a stable, conductive platform compatible with NV sensing.
Global Logistics: 6CCVD ensures reliable, global shipping (DDU default, DDP available) of sensitive quantum materials, minimizing lead times for critical research projects.

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

View Original Abstract

Water is one of the most important substances in the world. It is a crucial issue to study the dynamics of water molecules at interfaces or in the confined systems. In recent years, the emerging magnetic resonance technique based on nitrogen-vacancy (NV) center has allowed us to observe the nanoscale nuclear magnetic signal and temperature simultaneously. Here we succeed in measuring the nuclear magnetic resonance (NMR) signals of nanoscale solid and liquid water on diamond surface by NV center, and observing the solid-liquid phase transition of these nano-water by temperature control. This work demonstrates that the nano-NMR technique based on NV centers can probe the dynamics behavior of nanoscale materials effectively, providing a new way for studying the nanoscale confined systems.

Tech Support

Original Source

DOI: https://doi.org/10.7498/aps.71.20211348