# 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

## TL;DR

This study uses ab initio molecular dynamics to investigate how surface vibrations influence the descent pathways and rates of titanium adatoms on TiN surfaces, revealing temperature-dependent mechanisms.

## Contribution

It uncovers the significant role of surface vibrations in lowering activation energies and altering descent pathways of Ti adatoms on TiN surfaces at finite temperatures.

## Key findings

- Surface vibrations significantly lower activation energies for adatom descent.
- Descent rates via different pathways become comparable at T >= 1500 K.
- Vibrations modify the reaction pathway, enabling alternative descent mechanisms.

## Abstract

We carry out density-functional ab initio molecular dynamics (AIMD) simulations of Ti adatom (Tiad) migration on, and descent from, TiN <100>-faceted 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 Tiad descent via direct-hopping vs. push-out/exchange with a Ti island edge atom for T >= 1500 K. We demonstrate that the 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.

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Source: https://tomesphere.com/paper/1706.06487