Enhancement of thermal transfer at metal-amorphous silicon interfaces driven by inelastic phonon scattering

The purpose of this study is to investigate the effect of amorphization on thermal transport at metal-silicon interfaces. Recent atomistic simulations (El Hajj et al., 2024) have demonstrated a two to three fold increase of the interface thermal conductance at gold-amorphous silicon interfaces as compared to gold-crystalline silicon interfaces. The relative enhancement was attributed to the increased bonding between gold and silicon introduced by the amorphization. Here, we extend these considerations to copper and silver using a combination of Density Functional Theory, Non Equilibrium Green’s Function and Non Equilibrium Molecular dynamics. We show that amorphization of silicon leads to a relative enhancement of the interface thermal conductance though less pronounced as the gold-silicon system. To interpret these enhancements, we have decomposed the interfacial thermal spectrum in terms of an elastic and inelastic channels. This decomposition reveals that the relative enhancement of interfacial heat transfer is a result of a trade of between elastic and inelastic transport. On the one hand, amorphization leads to a decrease of the harmonic bonding at the interface, contrary to the case of gold-silicon interfaces. On the other hand, amorphization leads to higher degree of anharmonicity and consequently higher inelastic transport. This latter effect compensates the decrease of harmonic bonding and explains the net resulting higher interface thermal conductance. The analysis of the dynamical structure factor enables us to identify the nature of the energy carriers-diffusons vs propagons-which are involved in phonon transmission at metal-amorphous silicon interfaces. All these considerations help provide microscopic insights in thermal transfer at metal-amorphous semiconductors irrigating applications in thermal management of modern electronic devices and nanoparticle based thermal cancer therapies. • Report of an increase by 40 percents of the interfacial phonon transport at metal/silicon interfaces due to silicon amorphization. • Microscopic interpretation of this enhancement as due to a balance between elastic and inelastic phonon scattering at the interface. • Analysis of the nature of the energy carriers-diffusons versus propagons-at the metal-amorphous silicon interfaces.