[Paper Review] Thermal interface conductance between aluminum and aluminum oxide: A rigorous test of atomistic level theories

Murali Gopal Muraleedharan, Kiarash Gordiz+4 more|arXiv (Cornell University)|Jul 17, 2018

Thermal properties of materials36 references4 citations

TL;DR

This study presents the first accurate theoretical prediction of thermal interfacial conductance at the aluminum-sapphire (Al-α-Al2O3) interface using interfacial conductance modal analysis (ICMA), which achieves <5% mean error when compared to time-domain thermoreflectance (TDTR) experiments. ICMA outperforms atomistic Green's function (AGF) by incorporating full anharmonicity and a fundamental treatment of interfacial heat flux, revealing that over 90% of conductance arises from cross-correlated modes between Al and Al2O3 phonons.

ABSTRACT

We report the first ever accurate theoretical prediction of thermal conductance of any material interface. Thermal interfacial conductance of aluminum (Al)-sapphire (α-Al2O3) interface along crystal directions (111) Al || (0001) Al2O3 for temperature ranging from 50-500 K is calculated using two fundamentally different methods: interfacial conductance modal analysis (ICMA) and atomistic green function (AGF). While AGF overpredicts interfacial conductance, both the quantitative and qualitative predictions of ICMA are exceptional when compared with the time-domain thermoreflectance (TDTR) experimental data. The mean error in ICMA results are below 5%. We believe that the accurate theoretical prediction by ICMA can be credited to a more fundamental treatment of the interfacial heat flux in contrast to that of the phonon gas model (PGM) and inclusion of anharmonicity to full order. ICMA also gives the eigen mode level details revealing the nanoscale picture of heat transport: more than 90% of conductance is contributed by the cross correlation (interaction) between partially extended modes of Al and Al2O3 and the remaining is attributed to interfacial modes. This is a major milestone in combustion heat transfer research enabling materials scientists to rationally design propellant architectures to serve long-distance propulsion missions.

Motivation & Objective

• To achieve a first-principles theoretical prediction of thermal interfacial conductance at the Al-sapphire interface.
• To rigorously test atomistic-level theories of interfacial heat transfer against experimental data.
• To identify the physical mechanisms governing phonon-mediated heat transport across the Al/Al2O3 interface.
• To evaluate the accuracy and physical consistency of ICMA versus AGF in predicting interfacial conductance.

Proposed method

• Employed interfacial conductance modal analysis (ICMA), a method based on the exact solution of the interfacial heat flux operator in the harmonic approximation.
• Used atomistic Green's function (AGF) as a benchmark method, which treats phonon scattering at the interface via self-energy corrections.
• Calculated conductance over a temperature range of 50–500 K along the (111) Al || (0001) Al2O3 crystal orientation.
• Compared theoretical predictions directly with time-domain thermoreflectance (TDTR) experimental measurements.
• Incorporated full anharmonicity in ICMA to improve accuracy beyond the phonon gas model (PGM).
• Analyzed mode-specific contributions to conductance, distinguishing between interfacial modes and cross-correlated bulk-like modes.

Experimental results

Research questions

• RQ1 Can interfacial conductance at the Al-sapphire interface be accurately predicted from first principles using atomistic-level theories?
• RQ2 How do ICMA and AGF compare in predicting interfacial conductance, and which method better matches experimental data?
• RQ3 What is the relative contribution of interfacial modes versus cross-correlated bulk-like modes to the total thermal conductance?
• RQ4 To what extent does full anharmonicity improve the accuracy of theoretical predictions in interfacial heat transfer?
• RQ5 What is the physical origin of the dominant heat transfer pathways at the Al/Al2O3 interface?

Key findings

• ICMA achieved a mean error of less than 5% when compared to time-domain thermoreflectance (TDTR) experimental data across 50–500 K.
• ICMA provided accurate quantitative and qualitative predictions, while AGF overpredicted the interfacial conductance.
• Over 90% of the thermal conductance originated from cross-correlation between partially extended phonon modes of Al and Al2O3.
• The remaining conductance was attributed to interfacial modes, indicating that bulk-like mode coupling dominates heat transfer.
• The success of ICMA is attributed to its fundamental treatment of interfacial heat flux and inclusion of full anharmonicity, unlike the phonon gas model.
• The study establishes ICMA as a reliable framework for predicting interfacial conductance in complex material systems.