Atomic View of Surface Self-Diffusion: Tungsten on Tungsten

Ehrlich, Gert; Hudda, F. G.

doi:10.1063/1.1726787

Cited by 1,669 publications

(830 citation statements)

References 10 publications

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“…1, [48][49][50] Extensive research can be found in the literature on the kinetic instability. The step edge barriers also modify the mobility for the surface evolution under elastic effects.…”

Section: Introductionmentioning

confidence: 99%

Continuum model for the long-range elastic interaction on stepped epitaxial surfaces in2+1dimensions

Zhu

Xiang

2009

Phys. Rev. B

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In heteroepitaxy, the mismatch of lattice constants between the crystal film and the substrate causes misfit strain and stress in the bulk of the film, driving the surface of the film to self-organize into various nanostructures. Below the roughening transition temperature, an epitaxial surface consists of facets and steps and changes its morphology by lateral motion of steps. In this paper, we present a 2 + 1-dimensional continuum model for the long-range elastic interaction on stepped surface of a strained film. The continuum model is derived rigorously from the discrete model for the interaction between steps; thus it incorporates the discrete features of the stepped surfaces. Examples show that our continuum model is much more accurate as an approximation to the discrete model than the traditional continuum approximation. Moreover, in the linear instability of a planar surface, our continuum model gives the transition from step bunching instability to step undulation instability as the distance between adjacent steps increases, which agrees with the experimental observations and the results of discrete models and is missing using the traditional continuum approximation. Numerical simulations of the surface evolution using our model in the nonlinear regime show several different surface morphologies, including the morphology of step bunching which cannot be obtained using the traditional continuum approximation.

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Section: Introductionmentioning

confidence: 99%

Continuum model for the long-range elastic interaction on stepped epitaxial surfaces in2+1dimensions

Zhu

Xiang

2009

Phys. Rev. B

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“…13 A potentially attractive and unique feature of high-power pulsed magnetron sputtering (HIPIMS) 14 is the ability to ionize up to 90% of the sputtered metal flux, 15 depending upon the metal. Thus, HIPIMS offers the opportunity to increase momentum transfer to the growing film, while providing enhanced adatom mobilities and higher probabilities for overcoming Ehrlich step-edge barriers, 16,17,18,19 utilizing sputtered metal atoms which are ionized in the plasma. 20 Here, we report results of an investigation of the growth of polycrystalline Ti 1-x Al x N films by co-sputtering from separate elemental metal targets, Al and Ti, in a hybrid HIPIMS/DCMS configuration in order to selectively control the composition of metal ion fluxes during ionassisted growth.…”

Section: Introductionmentioning

confidence: 99%

Role of Tin+ and Aln+ ion irradiation (n=1, 2) during Ti1-xAlxN alloy film growth in a hybrid HIPIMS/magnetron mode

Greczyński

Johansson

et al. 2012

Surface and Coatings Technology

130

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Metastable Ti 1-x Al x N (0.4 ≤ x ≤ 0.76) films are grown using a hybrid approach in which high-power pulsed magnetron sputtering (HIPIMS) is combined with dc magnetron sputtering (DCMS). Elemental Al and Ti metal targets are co-sputtered with one operated in HIPIMS mode and the other target in DCMS; the positions of the targets are then switched for the next set of experiments. In both cases, the AlN concentration in the co-sputtered films, deposited at T s = 500 °C with R = 1.5-5.3 Å/s, is controlled by adjusting the average DCMS target power. Resulting films are analyzed by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, elastic recoil detection analysis, and nanoindentation.Mass spectroscopy is used to determine ion energy distribution functions at the substrate. The distinctly different flux distributions obtained from targets driven in HIPIMS vs. DCMS modes allow the effects of Al n+ and Ti n+ (n = 1, 2) ion irradiation on film growth kinetics, and resulting properties, to be investigated separately. Bombardment with Al n+ ions (primarily Al + in the Al-HIPIMS/Ti-DCMS configuration) during film growth leads to NaCl-structure Ti 1-x Al x N (0.53 ≤ x ≤ 0.60) films which exhibit high hardness (> 30 GPa) with low stress (0.2 -0.7 GPa tensile). In contrast, films with corresponding AlN concentrations grown under Ti n+ metal ion irradiation (with a significant Ti 2+ component) in the Ti-HIPIMS/Al-DCMS mode have much lower hardness, 18-19 GPa, and high compressive stress ranging up to 2.7 GPa. The surprisingly large variation in mechanical properties results from the fact that the kinetic AlN solubility limit x max in 2 Ti 1-x Al x N depends strongly on, in addition to T s and R, the target power configuration during growth and hence the composition of the ion flux. AlN with x max  64 mol% can be accommodated in the NaCl structure under Al n+ ion flux, compared with  40 mol% for growth with Ti n+ flux. The strong asymmetry in film growth reaction paths is due primarily to the fact that the doubly-ionized metal ion flux is approximately two orders of magnitude higher from the Ti target, than from Al, powered with HIPIMS. This asymmetry becomes decisive upon application of a moderate substrate bias voltage, -60 V, applied synchronously with HIPIMS pulses, during growth.

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“…4(b) of Ref. [2]. In addition, in the same STM image one can see modulation of the widths of worm-like pyramids (pearl-like substructures), corresponding to the arrays of small rounded mounds in Fig.…”

mentioning

confidence: 75%

“…Of paramount significance are adatom interactions with steps that form on the multilayered surface, particularly the energy barriers occurring near the step edges that inhibit adatom transitions between layers of the growing interface. These so-called step edge barriers were found by Ehrlich and Hudda [2], and further elucidated by Schwoebel [3] and Villain [4]. Ehrlich-Schwoebel-Villain (ESV) energy barriers produce up-hill adatom surface currents, from the terrace of the lower layer towards the terrace of the upper layer.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Interface Dynamics and Far-From-Equilibrium Phase Transitions in Multilayer Epitaxial Growth and Erosion on Crystal Surfaces: Continuum Theory Insights

Golubović

Levandovsky

Moldovan

2011

East Asian J. Appl. Math.

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Abstract. We review recent theoretical progress in the physical understanding of far-from-equilibrium phenomena seen experimentally in epitaxial growth and erosion on crystal surfaces. The formation and dynamics of various interface structures (pyramids, ripples, etc.), and also kinetic phase transitions observed between these structures, can all be understood within a simple continuum model based on the mass conservation law and respecting the symmetries of the growing crystal surface. In particular, theoretical predictions and experimental results are compared for (001), (110) and (111) crystal surfaces. 81.15.Aa, 89.75.Kd, 05.90.+m PACS (2006):

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Atomic View of Surface Self-Diffusion: Tungsten on Tungsten

Cited by 1,669 publications

References 10 publications

Continuum model for the long-range elastic interaction on stepped epitaxial surfaces in2+1dimensions

Continuum model for the long-range elastic interaction on stepped epitaxial surfaces in2+1dimensions

Role of Tin+ and Aln+ ion irradiation (n=1, 2) during Ti1-xAlxN alloy film growth in a hybrid HIPIMS/magnetron mode

Interface Dynamics and Far-From-Equilibrium Phase Transitions in Multilayer Epitaxial Growth and Erosion on Crystal Surfaces: Continuum Theory Insights

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