L\'evy-flight intermixing: anomalous nanoscale diffusion in Pt/Ti

TL;DR

This study reveals that atomic intermixing at the Pt/Ti interface during ion sputtering exhibits superdiffusive Le9vy flights, a novel observation for bulk interdiffusion, supported by molecular dynamics and ab initio calculations.

Contribution

It demonstrates the occurrence of Le9vy-flight-like superdiffusive atomic transport at the Pt/Ti interface, a phenomenon not previously reported in bulk interdiffusion.

Findings

Le9vy flights characterize atomic transport in Pt/Ti intermixing.

MD simulations show high-rate superdiffusive interfacial atomic transport.

The behavior explains the high diffusivity tail in experimental concentration profiles.

Abstract

Probing the anomalous nanoscale intermixing using molecular dynamics (MD) simulations in Pt/Ti bilayer we reveal the superdiffusive nature of interfacial atomic transport. It is shown that the Pt atoms undergo anomalous atomic transport across the anisotropic interface of Pt/Ti with suprisingly high rates which can be characterized as L\'evy flights. L\'evy flight is not a unique phenomenon in nature, however, no such events have been reported yet for bulk interdiffusion. In particular, the low-energy (0.5 keV) ion-sputtering induced transient enhanced intermixing has been studied by MD simulations. Ab initio density functional calculations have been used to check and reparametrize the employed heteronuclear interatomic potential. The L\'evy-intermixing behavior explains the high diffusity tail in the concentration profile obtained by Auger electron spectroscopy depth profiling (AES-DP) analysis in Pt/Ti bilayer (reported in ref.: P. S\"ule, {\em et al.}, J. Appl. Phys., {\bf 101}, 043502 (2007)).