Equilibrium Cu-Ag nanoalloy structure formation revealed by in situ scanning transmission electron microscopy heating experiments

Ping Lu,Blythe G. Clark,Paul Vianco,Timothy J. Boyle,Michael Chandross

doi:10.1063/1.4866052

Ping Lu, Blythe G. Clark + Show 3 more

Open Access

https://doi.org/10.1063/1.4866052

Copy DOI

Journal: APL materials	Publication Date: Feb 1, 2014
Citations: 41	License type: cc-by

Affiliation: Sandia National Laboratories

Abstract

Using in situ scanning transmission electron microscopy heating experiments, we observed the formation of a 3-dimensional (3D) epitaxial Cu-core and Ag-shell equilibrium structure of a Cu-Ag nanoalloy. The structure was formed during the thermal interaction of Cu(∼12 nm) and Ag NPs(∼6 nm) at elevated temperatures (150–300 °C) by the Ag NPs initially wetting the Cu NP along its {111} surfaces at one or multiple locations forming epitaxial Ag/Cu (111) interfaces, followed by Ag atoms diffusing along the Cu surface. This phenomenon was confirmed through Monte Carlo simulations to be a nanoscale effect related to the large surface-to-volume ratio of the NPs.

Highlights

New physical and chemical phenomena related to nanoscale effects are currently the focus of intense research.[1,2,3,4] Nanoparticles (NPs) are characterized by small volumes and a large number of surface atoms, which inherently possess a significantly larger mobility than bulk atoms
For the metallic copper (Cu) and silver (Ag) system, it is well known that the solid solution of the binary Ag-Cu alloy is unstable, and upon heating an initially amorphous or nanocrystalline Ag-Cu alloy in bulk form will separate into Ag and Cu phases due to the large miscibility gap and positive enthalpy of mixing for this eutectic system.[8,9,10,11]
The present study is designed to better understand these questions by thermally reacting Cu (∼12 nm) and Ag NPs (∼6 nm) and observing the reaction processes and products using in situ scanning transmission electron microscopy (STEM)

Summary

Introduction

New physical and chemical phenomena related to nanoscale effects are currently the focus of intense research.[1,2,3,4] Nanoparticles (NPs) are characterized by small volumes and a large number of surface atoms, which inherently possess a significantly larger mobility than bulk atoms.

Results

Conclusion