AVS 60th International Symposium and Exhibition
    Thin Film Thursday Sessions
       Session TF+PS-ThM

Paper TF+PS-ThM11
Ab-initio and Classical Molecular Dynamics Study of Diffusion of Ti and N Adatoms on the TiN(001) Surface

Thursday, October 31, 2013, 11:20 am, Room 102 C

Session: Advanced CVD Methods
Presenter: D.G. Sangiovanni, Linköping University, Sweden
Authors: D.G. Sangiovanni, Linköping University, Sweden
D. Edström, Linköping University, Sweden
L. Hultman, Linköping University, Sweden
I.G. Petrov, University of Illinois at Urbana Champaign
J.E. Greene, University of Illinois at Urbana Champaign
V. Chirita, Linköping University, Sweden
Correspondent: Click to Email
We carry out ab-initio and classical molecular dynamics (MD) simulations to investigate fundamental atomistic processes and surface properties responsible for TiN surface evolution during thin film growth. We find that Ti adatoms are highly mobile on TiN(001) terraces where they diffuse between fourfold hollow sites primarily via <100> channels. <110> diffusion via atop N terrace atoms, double and triple <100> jumps are also observed, and their occurrence is a function of TiN(001) temperature. When placed on TiN/TiN(001) islands, Ti adatoms funnel toward cluster edges and corners, where they rapidly descend by either direct hopping or push/out-exchange. Ti and N adatoms diffusion on square islands is anisotropic and results in preferential channels for mass transport. N adatoms, considerably less mobile than Ti adatoms, can form strong chemical bonds with underlying terrace or island N atoms. As an effect of this bonding, N adatoms can diffuse on TiN(001) terraces by exchange with N terrace atoms. At high temperatures, the rapid lattice vibrations assist the desorption of N2 (N-adatom/N-terrace) dimers, and anion vacant sites are produced in the TiN(001) terrace. When placed on square TiN/TiN(001) clusters, N adatoms can pull Ti corner atoms onto the island to form TiN dimers which descend via direct hop over the island edge. Both N and Ti adatoms slowly diffuse along island edges. In contrast, due to the high degree of ionicity in Ti-N bonds, Ti and N adatoms easily diffuse around island corners of the same chemical type via 1D push-out/exchange due to electrostatic repulsion. Corners of opposite chemical type are rapidly rounded by direct diffusion. Finally, we combine the Arrhenius plots obtained from classical, and quantum-mechanical simulations to determine, with high accuracy, Ti and N adatom diffusion energy barriers and diffusion coefficients on TiN(001 ). The excellent agreement between empirical and ab-initio methods results further demonstrates the ability of classical interaction potentials for accurate, fully-deterministic, simulations of thin films deposition.