Surface Crystallization in a Liquid AuSi Alloy

TL;DR

This study reveals a crystalline monolayer on the surface of liquid AuSi alloy, with an unusually deep atomic layering, challenging previous understanding of liquid metal surfaces and suggesting new insights into amorphous alloy models.

Contribution

First observation of a crystalline monolayer on a liquid alloy surface with unprecedented layering depth, expanding knowledge of liquid metal surface structures.

Findings

Crystalline monolayer detected at the liquid AuSi surface.

Layering depth exceeds that of all previously studied liquid metals.

Surface crystallinity occurs despite lack of stable bulk crystalline phases.

Abstract

X-ray measurements reveal a crystalline monolayer at the surface of the eutectic liquid Au_{82}Si_{18}, at temperatures above the alloy's melting point. Surface-induced atomic layering, the hallmark of liquid metals, is also found below the crystalline monolayer. The layering depth, however, is threefold greater than that of all liquid metals studied to date. The crystallinity of the surface monolayer is notable, considering that AuSi does not form stable bulk crystalline phases at any concentration and temperature and that no crystalline surface phase has been detected thus far in any pure liquid metal or nondilute alloy. These results are discussed in relation to recently suggested models of amorphous alloys.