Surface melting of nanoscopic epitaxial films

TL;DR

This paper investigates how interface interactions and elastic stresses influence surface melting in nanoscopic epitaxial films, revealing conditions for boosted premelting and overheating phenomena.

Contribution

It introduces a new interaction quantity G to describe interface effects, showing how it modifies premelting behavior in thin solid films.

Findings

Positive G enhances premelting with a two-stage process.

Negative G prevents premelting, causing overheating.

Elastic stresses alter melting curves significantly.

Abstract

By introducing finite size surface and interfacial excess quantities, interactions between interfaces are shown to modify the usual surface premelting phenomenon. It is the case of surface melting of a thin solid film s deposited on a planar solid substrate S. More precisely to the usual wetting condition of the solid s by its own melt l, necessary for premelting (wetting factor F<0), is adjoined a new quantity G describing the interactions of the l/s interface with the s/S interface. When G>0 this interface attraction boosts the premelting so that a two stage boosted surface premelting is foreseen: a continuous premelting, up to roughly half the deposited film, is followed by an abrupt first order premelting. When G<0 these interfaces repell each other so that premelting is refrained and the film remains partly solid above the bulk melting point (overheating) what is called astride melting. Elastic stress modifies both types of melting curves. Bulk and surface stresses have to be distinguished.