Thermal Transport Properties of Diamond Phonons by Electric Field

At a Glance

Metadata	Details
Publication Date	2022-09-28
Journal	Nanomaterials
Authors	Yongsheng Zhao, Fengyun Yan, Xue Liu, Hongfeng Ma, Zhenyu Zhang
Institutions	Lanzhou University of Technology
Citations	3
Analysis	Full AI Review Included

Technical Documentation: Electric Field Modulation of Diamond Thermal Transport

This document analyzes the research on controlling diamond’s thermal transport properties via external electric fields, providing technical specifications and outlining how 6CCVD’s advanced MPCVD diamond materials and customization services enable the replication and extension of this groundbreaking work for next-generation thermal management applications.

Executive Summary

The research demonstrates the feasibility of actively tuning the lattice thermal conductivity ($\kappa$) of diamond using external electric fields, a critical breakthrough for high-power electronics and quantum technology.

Active Thermal Modulation: External electric fields (E-fields) can significantly modulate diamond’s thermal conductivity, increasing it by up to 36.1% or decreasing it by 34% at 300 K.
Anisotropic Response: The thermal response is highly dependent on crystal orientation, with the [111] direction showing the most pronounced modulation effect.
Mechanism Confirmed: The E-field breaks the diamond lattice symmetry, altering the electron density distribution, which subsequently changes the phonon mean free path (MFP) and phonon-phonon interaction strength, primarily affecting phonons below 30 THz.
High-Power Relevance: This tunability is essential for developing advanced diamond heat sinks capable of dynamic thermal management in high-power Insulated Gate Bipolar Transistor (IGBT) equipment and integrated circuits.
Material Requirement: Achieving these theoretical thermal properties requires ultra-high purity, low-defect Single Crystal Diamond (SCD) substrates, which 6CCVD specializes in producing via MPCVD.

Technical Specifications

The following table summarizes the key quantitative findings regarding diamond’s thermal response to electric fields, extracted from the first-principles calculations (T = 300 K).

Parameter	Value	Unit	Context
Benchmark Lattice Thermal Conductivity ($\kappa$)	1960.80	W·m^-1K^-1	Calculated at 0 a.u. E-field
Maximum $\kappa$ Achieved	2654	W·m^-1K^-1	[111] orientation, E = +0.004 a.u.
Minimum $\kappa$ Achieved	1283	W·m^-1K^-1	[111] orientation, E = -0.004 a.u.
Maximum $\kappa$ Increase Rate ($\Delta \kappa / \kappa$)	36.1	%	[111] orientation, E = +0.004 a.u.
Maximum $\kappa$ Decrease Rate ($\Delta \kappa / \kappa$)	-34	%	[111] orientation, E = -0.004 a.u.
Critical E-Field Strength (Microscopic)	±0.004	a.u.	Used for maximum modulation
Critical E-Field Strength (Macroscopic)	$\approx \pm 2.06 \times 10^{9}$	V·cm^-1	Applied along [111] direction
Temperature Range Studied	240 - 500	K	Thermal conductivity analysis range
Phonon Frequency Range Affected	< 30	THz	Range showing primary E-field response
C-C Bond Length (Fixed)	1.547	Å	Unchanged by E-field application

Key Methodologies

The study utilized advanced first-principles calculations to model the electron-phonon coupling and thermal transport response of diamond under a uniform electric field.

Computational Framework: First-principles calculations were performed using the ABINIT software package, leveraging Density-Functional Perturbation Theory (DFPT) to analyze phonon properties.
Thermal Transport Calculation: Lattice thermal conductivity ($\kappa$) was calculated using the Phono3py package, which employs the finite displacement method to determine second-order and third-order force constants.
Transport Equation Solution: The Boltzmann phonon transport equations (BTE) were solved using the single-mode relaxation time approximation (RTA) method.
Electric Field Application: A uniform electric field was applied directly to the diamond primitive cell, simulating two parallel electrode plates sandwiching the bulk material.
Crystallographic Analysis: Calculations were performed across three major crystal orientation groups: <100>, <110>, and <111>, to investigate anisotropic effects.
Convergence Parameters: High-precision convergence was ensured using a $12 \times 12 \times 12$ grid for the Brillouin zone and a $56 \times 56 \times 56$ q grid for thermal conductivity calculations.

6CCVD Solutions & Capabilities

This research confirms that SCD diamond is not merely a passive heat spreader but an actively tunable thermal material, provided the material quality is sufficient to support the theoretical thermal properties. 6CCVD is uniquely positioned to supply the high-purity, customized SCD required for experimental validation and device integration of this technology.

Applicable Materials

To replicate and extend this research, the highest quality, low-defect material is essential to minimize intrinsic scattering and achieve the benchmark thermal conductivity ($\approx 2000 \text{ W}\cdot\text{m}^{-1}\text{K}^{-1}$).

Optical Grade Single Crystal Diamond (SCD): Required for achieving ultra-high purity and low nitrogen/defect concentrations, ensuring the intrinsic phonon properties necessary for E-field modulation are preserved.
Custom Orientation SCD: Since the [111] direction showed the maximum thermal modulation (36.1% increase), 6CCVD offers custom SCD growth specifically oriented along the [111] axis to maximize device performance.

Customization Potential for Device Integration

Implementing E-field modulation requires precise material engineering and integration of electrodes capable of handling high voltages (up to $2 \times 10^{9} \text{ V}\cdot\text{cm}^{-1}$ across the lattice).

Requirement from Research	6CCVD Customization Capability	Benefit to Researcher/Engineer
High-Purity Substrates	SCD plates/wafers up to 500 µm thick, Ra < 1 nm polished.	Ensures low intrinsic scattering, maximizing the baseline thermal conductivity and E-field effect.
Specific Crystal Orientation	Custom growth of [111] oriented SCD.	Enables maximum thermal tunability (36.1% modulation) as predicted by the calculations.
Electrode Integration	In-house metalization services: Au, Pt, Pd, Ti, W, Cu.	Allows for direct fabrication of parallel plate electrodes necessary to apply the uniform E-field for experimental validation.
Custom Dimensions	Plates/wafers up to 125 mm (PCD) or custom SCD dimensions.	Supports prototyping and scaling of E-field tunable diamond heat sinks for high-power devices (e.g., IGBTs).
Substrate Thickness	SCD/PCD substrates up to 10 mm thick.	Provides robust platforms for high-voltage testing and integration into complex thermal stacks.

Engineering Support

6CCVD’s in-house PhD team specializes in the fundamental physics and engineering of MPCVD diamond. We offer comprehensive support for projects focused on:

E-field Tunable Thermal Management: Assisting researchers in selecting the optimal SCD orientation and purity grade to experimentally validate the predicted thermal modulation effects.
High-Frequency Phonon Engineering: Consulting on material specifications (e.g., isotopic purity) to further manipulate phonon scattering mechanisms in conjunction with external fields.
Advanced Semiconductor Integration: Providing material solutions for high-power IGBT and quantum sensor applications where dynamic thermal control is paramount.

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

View Original Abstract

For the preparation of diamond heat sinks with ultra-high thermal conductivity by Chemical Vapor Deposition (CVD) technology, the influence of diamond growth direction and electric field on thermal conductivity is worth exploring. In this work, the phonon and thermal transport properties of diamond in three crystal orientation groups (<100>, <110>, and <111>) were investigated using first-principles calculations by electric field. The results show that the response of the diamond in the three-crystal orientation groups presented an obvious anisotropy under positive and negative electric fields. The electric field can break the symmetry of the diamond lattice, causing the electron density around the C atoms to be segregated with the direction of the electric field. Then the phonon spectrum and the thermodynamic properties of diamond were changed. At the same time, due to the coupling relationship between electrons and phonons, the electric field can affect the phonon group velocity, phonon mean free path, phonon-phonon interaction strength and phonon lifetime of the diamond. In the crystal orientation [111], when the electric field strength is ±0.004 a.u., the thermal conductivity is 2654 and 1283 W·m−1K−1, respectively. The main reason for the change in the thermal conductivity of the diamond lattice caused by the electric field is that the electric field has an acceleration effect on the extranuclear electrons of the C atoms in the diamond. Due to the coupling relationship between the electrons and the phonons, the thermodynamic and phonon properties of the diamond change.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano12193399

References

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