# Thermal Boundary Characteristics of Homo-/Heterogeneous Interfaces

## TL;DR

This study uses ReaxFF MD simulations and phenomenological theory to analyze thermal boundary resistance at solid interfaces, revealing how chemical reactivity influences TBR and enabling design of multi-layered structures.

## Contribution

It combines ReaxFF MD and phenomenological theory to characterize thermal boundary resistance at reactive and non-reactive interfaces, providing new insights into interface design.

## Key findings

- Reactive interfaces have twice the TBR of non-reactive ones.
- A stable amorphous layer forms at reactive interfaces, increasing TBR.
- Temperature profiles differ between homogeneous and heterogeneous interfaces.

## Abstract

The interface of two solids in contact introduces a thermal boundary resistance (TBR), which is challenging to measure from experiments. Besides, if the interface is reactive, it can form an intermediate recrystallized or amorphous region, and extra influencing phenomena are introduced. Reactive force field Molecular Dynamics (ReaxFF MD) is used to study these interfacial phenomena at the (non-)reactive interface. The non-reactive interfaces are compared using a phenomenological theory (PT), predicting the temperature discontinuity at the interface. By connecting ReaxFF MD and PT we confirm a continuous temperature profile for the homogeneous non-reactive interface and a temperature jump in case of the heterogeneous non-reactive interface. ReaxFF MD is further used to understand the effect of chemical activity of two solids in contact. The selected Si/SiO$_2$ materials showed that the TBR of the reacted interface is two times larger than the non-reactive, going from $1.65\times 10^{-9}$ to $3.38\times 10^{-9}$ m$^2$K/W. This is linked to the formation of an intermediate amorphous layer induced by heating, which remains stable when the system is cooled again. This provides the possibility to design multi-layered structures with a desired TBR.