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Flux dependent MeV self-ion-induced effects on Au nanostructures: dramatic mass transport and nanosilicide formation.

Research paper by J J Ghatak, M M Umananda Bhatta, B B Sundaravel, K G M KG Nair, Sz-Chian SC Liou, Cheng-Hsuan CH Chen, Yuh-Lin YL Wang, P V PV Satyam

Indexed on: 13 Aug '08Published on: 13 Aug '08Published in: Nanotechnology



Abstract

We report a direct observation of dramatic mass transport due to 1.5 MeV Au(2+) ion impact on isolated Au nanostructures of average size ≈7.6 nm and height ≈6.9 nm that are deposited on Si(111) substrate under high flux (3.2 × 10(10)-6.3 × 10(12) ions cm(-2) s(-1)) conditions. The mass transport from nanostructures was 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 redistribution. The mass transport is explained on the basis of thermal effects and the creation of rapid diffusion paths in the nanoscale regime during the course of ion irradiation. The unusual mass transport is found to be associated with the formation of gold silicide nano-alloys at subsurfaces. The complexity of the ion-nanostructure interaction process is discussed with a direct observation of melting (in the form of spherical fragments on the surface) phenomena. Transmission electron microscopy, scanning transmission electron microscopy, and Rutherford backscattering spectroscopy methods have been used.