Ti adatom diffusion on TiN(001): Ab initio and classical molecular dynamics simulations

SURFACE SCIENCE

卷:627

Article

Sangiovanni, D. G.¹  Edstrom, D.¹  Hultman, L.¹  Petrov, I.^1,2,3,4  Greene, J. E.^1,2,3,4  Chirita, V.¹ 

[1] Linkoping Univ, Dept Phys Chem & Biol IFM, SE-58183 Linkoping, Sweden

[2] Univ Illinois, Dept Mat Sci, Urbana, IL 61801 USA

[3] Univ Illinois, Dept Phys, Urbana, IL 61801 USA

[4] Univ Illinois, Frederick Seitz Mat Res Lab, Urbana, IL 61801 USA

关键词: Surface diffusion;    Nitrides;    Molecular dynamics simulations;    Density functional theory;   

DOI  :  10.1016/j.susc.2014.04.007

来源: Elsevier

【 摘 要 】

Ab initio and classical molecular dynamics (AIMD and CMD) simulations reveal that Ti adatoms on TiN(001) surfaces migrate between neighboring fourfold hollow sites primarily along in-plane <100> channels. <100> and <110> single jumps, as well as <100> double jump rates, obtained directly from MD runs as a function of temperature, are used to determine diffusion activation energies Ea, and attempt frequencies A, for the three preferred Ti adatom migration pathways on TiN(001). From transition rates Aexp[-Ea / (k(B)T)], we determine adatom surface distribution probabilities as a function of time, which are used to calculate adatom diffusion coefficients D(T). AIMD and CMD predictions are consistent and complementary. Using CMD, we investigate the effect on the adatom jump rate of varying the phonon wavelength degrees of freedom by progressively increasing the supercell size. We find that long-wavelength phonons significantly contribute to increasing adatom mobilities at temperatures <= 600 K, but not at higher temperatures. Finally, by directly tracking the Ti adatom mean-square displacement during CMD runs, we find that Ti adatom jumps are highly correlated on TiN(001), an effect that yields lower D-s values (D-s(corr)) than those estimated from uncorrelated transition probabilities. The temperature-dependent diffusion coefficient is D-s(corr) (T) = (4.5 x 10(-4) Cm-2 s(-1)) exp[-0.55 eV / (k(B)T)]. (C) 2014 Elsevier I3.V. All rights reserved.

【 授权许可】

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