AVS 59th Annual International Symposium and Exhibition
    Thin Film Tuesday Sessions
       Session TF+AS-TuA

Paper TF+AS-TuA4
The Dynamics of Atomic-Scale Transport on the Anisotropic Compound Surface TiN(001)

Tuesday, October 30, 2012, 3:00 pm, Room 10

Session: Modeling and Analysis of Thin Films
Presenter: V. Chirita, Linköping University, Sweden
Authors: D.G. Sangiovanni, Linköping University, Sweden
V. Chirita, Linköping University, Sweden
L. Hultman, Linköping University, Sweden
I. Petrov, University of Illinois at Urbana Champaign
J.E. Greene, University of Illinois at Urbana Champaign
Correspondent: Click to Email
We use classical molecular dynamics (MD) and the modified embedded atom method (MEAM) formalism to investigate the dynamics of atomic-scale transport on a low index anisotropic model compound, TiN(001). Our simulations, totaling 0.25 ms for each case study, follow the pathways and migration kinetics of Ti and N adatoms, as well as TiNx complexes with x = 1, 2 and 3, all of which are known to contribute to the growth of TiN thin films by reactive deposition from Ti, N2, and N precursors. The simulations are carried out at 1000 K, a reasonable temperature for TiN(001) epitaxial growth. We find Ti adatoms to be the highest mobility species on TiN(001), with the primary migration path involving jumps of one nearest-neighbor distance dNN between four-fold hollow sites along in-plane <100> channels. Long jumps, 2dNN, are also observed, but at much lower frequency. N adatoms exhibit much lower migration rates than Ti, diffuse only along in-plane <110> directions, and are unstable to associative formation of N2 molecules which desorb at kinetic rates. As expected, TiN and TiN3 complexes migrate at even lower rates with complex diffusion pathways involving rotations, translations, and roto-translations. TiN2 trimers, however, are shown to have surprisingly high diffusion rates, comparable to that of Ti adatoms, due to, as revealed in our density functional theory (DFT) investigations, the significantly more symmetric charge transfer between trimer and terrace atoms, as compared with the charge distributions observed for dimers and tetramers.