Determination of Size Effects during the Phase Transition of a Nanoscale Au-Si Eutectic

B J. Kim, School of Materials Engineering and Birck Nanotechnology Center, Purdue University
J Tersoff, IBM Research Division, TJ Watson Research Center
C-Y Wen, School of Materials Engineering and Birck Nanotechnology Center, Purdue University
M C. Reuter, IBM Research Division, TJ Watson Research Center
E A. Stach, Birck Nanotechnology Center and School of Materials Engineering, Purdue University
F M. Ross, IBM Research Division, TJ Watson Research Center

Abstract

The phase diagram of a nanoscale system can be substantially different than in the bulk, but quantitative measurements have proven elusive. Here we use in situ microscopy to observe a phase transition in a nanoscale system, together with a simple quantitative model to extract the size effects from these measurements. We expose a Au particle to disilane gas, and observe the transition from a two-phase Au þ AuSi system to single-phase AuSi. Size effects are evident in the nonlinear disappearance of the solid Au. Our analysis shows a substantial shift in the liquidus line, and a discontinuous change in the liquid composition at the transition. It also lets us estimate the liquid-solid interfacial free energy.

Discipline(s)

Engineering