Effects of surface vibrations on interlayer mass transport: Ab initio molecular dynamics investigation of Ti adatom descent pathways and rates from TiN/TiN(001) islands

We carried out density-functional ab initio molecular dynamics (AIMD) simulations of Ti adatom (Ti-ad ) migration on, and descent from, square TiN(100) epitaxial islands on TiN(001) at temperatures (T) ranging from 1200 to 2400 K. Adatom-descent energy barriers determined via ab initio nudged-elastic-band calculations at 0 Kelvin suggest that Ti interlayer transport on TiN(001) occurs essentially exclusively via direct hopping onto a lower layer. However, AIMD simulations reveal comparable rates for Ti-ad descent via direct hopping vs push-out/exchange with a Ti island-edge atom for T amp;gt;= 1500 K. We demonstrate that this effect is due to surface vibrations, which yield considerably lower activation energies at finite temperatures by significantly modifying the adatom push-out/exchange reaction pathway.Funding Agencies|Olle Engkvist Foundation [2016/408]; Swedish Research Council (VR) Linkoping Linnaeus Initiative (LiLi-NFM) [2008-6572, 2014-5790, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials (Swedenapos;s innovation agency VINNOVA) [MatLiU 2009-00971]; Knut and Alice Wallenberg Foundation [2011.0094]