Flux dependent MeV self-ion- induced effects on Au nanostructures: Dramatic mass transport and nano-silicide formation

TL;DR

This study investigates how high-flux 1.5 MeV Au2+ ion irradiation causes significant mass transport and gold silicide formation in Au nanostructures on Si(111), revealing flux-dependent effects and nano-scale diffusion mechanisms.

Contribution

It provides the first detailed analysis of flux-dependent mass transport and silicide formation in Au nanostructures under MeV ion irradiation, combining experimental observations with simulations.

Findings

Mass transport extends up to 60 nm into substrate.

Flux significantly influences mass redistribution.

Formation of gold silicide nanoalloys observed.

Abstract

We report a direct observation of dramatic mass transport due to 1.5 MeV Au2+ ion impact on isolated Au nanostructures of an average size 7.6 nm and a height 6.9 nm that are deposited on Si (111) substrate under high flux (3.2x10^10 to 6.3x10^12 ions cm-2 s-1) conditions. The mass transport from nanostructures found to extend up to a distance of about 60 nm into the substrate, much beyond their size. This forward mass transport is compared with the recoil implantation profiles using SRIM simulation. The observed anomalies with theory and simulations are discussed. At a given energy, the incident flux plays a major role in mass transport and its re-distribution. The mass transport is explained on the basis of thermal effects and creation of rapid diffusion paths at nano-scale regime during the course of ion irradiation. The unusual mass transport is found to be associated with the formation of gold silicide nanoalloys at sub-surfaces. The complexity of the ion-nanostructure interaction process has been discussed with a direct observation of melting (in the form of spherical fragments on the surface) phenomena. The transmission electron microscopy, scanning transmission electron microscopy and Rutherford backscattering spectroscopy methods have been used.