Low-Energy Electron Microscopy Studies of Interlayer Mass Transport Kinetics on TiN(111)

TL;DR

This study uses in situ low-energy electron microscopy to investigate the interlayer mass transport kinetics during annealing of TiN(111) mounds, revealing surface diffusion as the rate-limiting process with high step permeability and temperature-dependent step interactions.

Contribution

It provides the first detailed kinetic analysis of TiN(111) mound decay, identifying surface diffusion as the dominant mechanism and quantifying step permeability and interactions.

Findings

Island decay rate is constant at each temperature.

Activation energy for decay is approximately 2.8 eV.

Surface diffusion controls the decay process, not bulk diffusion.

Abstract

In situ low-energy electron microscopy was used to study interlayer mass transport kinetics during annealing of three-dimensional (3D) TiN(111) mounds, consisting of stacked 2D islands, at temperatures T between 1550 and 1700 K. At each T, the islands decay at a constant rate, irrespective of their initial position in the mounds, indicating that mass is not conserved locally. From temperature-dependent island decay rates, we obtain an activation energy of 2.8+/-0.3 eV. This is consistent with the detachment-limited decay of 2D TiN islands on atomically-flat TiN(111) terraces [Phys. Rev. Lett. 89 (2002) 176102], but significantly smaller than the value, 4.5+/-0.2 eV, obtained for bulk-diffusion-limited spiral step growth [Nature 429, 49 (2004)]. We model the process based upon step flow, while accounting for step-step interactions, step permeability, and bulk mass transport. The results show that TiN(111) steps are highly permeable and exhibit strong repulsive temperature-dependent step-step interactions that vary between 0.003 and 0.076 eV-nm. The rate-limiting process controlling TiN(111) mound decay is surface, rather than bulk, diffusion in the detachment-limited regime.