| 1. |
- Abrasonis, Gintautas, et al.
(author)
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Nanoscale precipitation patterns in carbon-nickel nanocomposite thin films: Period and tilt control via ion energy and deposition angle
- 2010
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In: JOURNAL OF APPLIED PHYSICS. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 108:4, s. 043503-
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Journal article (peer-reviewed)abstract
- Periodic precipitation patterns in C:Ni nanocomposites grown by energetic ion codeposition are investigated. Films were grown at room temperature by ionized physical vapor deposition using a pulsed filtered cathodic vacuum arc. We reveal the role of the film composition, ion energy and incidence angle on the film morphology using transmission electron microscopy and grazing incidence small angle x-ray scattering. Under these growth conditions, phase separation occurs in a thin surface layer which has a high atomic mobility due to energetic ion impacts. This layer is an advancing reaction front, which switches to an oscillatory mode, producing periodic precipitation patterns. Our results show that the ion induced atomic mobility is not random, as it would be in the case of thermal diffusion but conserves to a large extent the initial direction of the incoming ions. This results in a tilted pattern under oblique ion incidence. A dependence of the nanopattern periodicity and tilt on the growth parameters is established and pattern morphology control via ion velocity is demonstrated.
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| 2. |
- Tucker, Mark, et al.
(author)
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A combinatorial investigation of sputtered Ta-Al-C thin films
- 2014
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In: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 558, s. 99-103
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Journal article (peer-reviewed)abstract
- We describe a combinatorial experiment investigating the Ta-Al-C material system, conducted with the aim of determining why the tantalum-containing M-n + (1)AX(n) phases have so far proved to be not amenable to thin-film synthesis. Samples were deposited onto (0001) Al2O3 wafers at 850 degrees C and characterized by X-ray diffraction wafer maps, scanning electron microscopy, and surface optical scattering. Elemental Ta, the binary phases TaC, Ta2C, and TaAl3, and the ternary phases Ta3Al2C and Ta5Al3C were identified. The morphology, phase composition and preferred orientation of the films deposited were found to be highly sensitive to the Ta fraction of the incident flux during deposition. No MAX phase material was observed, indicating that the Ta-containing MAX phases do not form under the deposition conditions investigated. Explanations associated with inadequate coverage of stochiometries, preferential sputtering, and thermodynamic instability have been ruled out. An explanation based on reduced surface diffusion of Ta during growth is proposed. A substantially higher substrate temperature during deposition is likely to be required to synthesize Ta-containing MAX phases.
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| 3. |
- Tucker, Mark D, et al.
(author)
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Substrate orientation effects on the nucleation and growth of the M(n+1)AX(n) phase Ti2AlC
- 2011
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In: JOURNAL OF APPLIED PHYSICS. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 109:1, s. 014903-
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Journal article (peer-reviewed)abstract
- The M(n+1)AX(n) (MAX) phases are ternary compounds comprising alternating layers of a transition metal carbide or nitride and a third "A-group" element. The effect of substrate orientation on the growth of Ti2AlC MAX phase films was investigated by studying pulsed cathodic arc deposited samples grown on sapphire cut along the (0001), (10 (1) over bar0), and (1 (1) over bar 02) crystallographic planes. Characterization of these samples was by x-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy. On the (10 (1) over bar0) substrate, tilted (10 (1) over bar8) growth of Ti2AlC was found, such that the TiC octahedra of the MAX phase structure have the same orientation as a spontaneously formed epitaxial TiC sublayer, preserving the typical TiC-Ti2AlC epitaxial relationship and confirming the importance of this relationship in determining MAX phase film orientation. An additional component of Ti2AlC with tilted fiber texture was observed in this sample; tilted fiber texture, or axiotaxy, has not previously been seen in MAX phase films.
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