Fuzzy nanostructure growth on Ta/Fe by He plasma irradiation

Kajita, Shin; Ishida, T.; Ohno, Noriyasu; Hwangbo, Dogyun; Yoshida, Tomoko

doi:10.1038/srep30380

Cited by 51 publications

(36 citation statements)

References 37 publications

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“…Linear fiber growth was also observed on Re surface 3406065-2 exposed to He plasma at high surface temperature [9]. It is noted that the crystal structure of Ru and Re is HCP.…”

Section: Ruthenium (Ru)mentioning

confidence: 71%

“…And a molecular dynamics (MD) simulation showed that yield strength of W fiber reduces significantly when He atoms were embedded [8]. Following these studies, the relationship between fuzz formation and shear modulus was discussed [9]; the fuzz was easily formed on high shear modulus metals such as W, Molyb- denum (Mo) and rhenium (Re), [10][11][12]. However, morphology changes induced by He plasma irradiation were not well-researched in other high shear modulus metals including rhodium (Rh) and ruthenium (Ru), which are facecentered cubic (FCC) and hexagonal close-packed (HCP), respectively.…”

Section: Introductionmentioning

confidence: 99%

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Nanostructure Growth on Rhodium/Ruthenium by the Exposure to He Plasma

Nojima

Kajita

Yoshida

et al. 2018

Plasma and Fusion Research

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Rhodium and ruthenium thin film coatings were conducted on tungsten samples by using a magnetron sputtering device; then, we irradiated He plasma to the samples in the linear plasma device NAGDIS-II (Nagoya Divertor Simulator). Fuzzy nanostructures were formed on rhodium and ruthenium samples when the surface temperatures were ∼950 and ∼1200 K, respectively. When the surface temperature was high, i.e., >1200 K, it was found that tungsten atoms diffused across the rhodium film and reached the film surface, and tungsten-fuzz was formed over the rhodium layer. From TEM analysis of ruthenium fibers, it was identified that there were thin parts in the fibers, and some fibers had no He bubbles. It was likely that fiber growth mechanism on ruthenium was different from the other metals.

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“…Linear fiber growth was also observed on Re surface 3406065-2 exposed to He plasma at high surface temperature [9]. It is noted that the crystal structure of Ru and Re is HCP.…”

Section: Ruthenium (Ru)mentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Nanostructure Growth on Rhodium/Ruthenium by the Exposure to He Plasma

Nojima

Kajita

Yoshida

et al. 2018

Plasma and Fusion Research

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“…Nevertheless, it was hypothesized that higher aspect ratio surface structures (similar to fuzz) could be formed at higher fluences since surface pores are known to be a precursor to fuzz formation in W 9 . To our knowledge, fuzz formation has never been observed in Ta except for in a very recent study23 that showed for the first time fuzz formation in Ta using sufficiently high He + ion fluences.…”

mentioning

confidence: 86%

Effect of high-flux, low-energy He+ ion irradiation on Ta as a plasma-facing material

Novakowski

Tripathi

Hassanein

2016

Sci Rep

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The goal of this work is to assess Ta as a potential plasma-facing material for future fusion reactors in terms of its response to high-flux, low-energy He+ ion irradiation. Ta samples were irradiated with 100 eV He+ ions at various fluences up to 3.5 × 1025 ions m−2 while simultaneously heated at constant temperatures in the range 823–1223 K. SEM studies show that irradiated Ta surfaces undergo significant morphology changes that have a strong dependence on both ion fluence and sample temperature. Optical reflectivity complements SEM and demonstrates a vertical growth of surface structures with increasing fluence. Ex situ XPS and XRD both show significant oxidation of the irradiated Ta surfaces, giving further qualitative information on the extent of surface modification. Overall, these irradiation-induced structures on Ta are similar to early-stage “fuzz” structures observed in W. However, Ta exhibits a higher fluence threshold for structure formation. While Ta may have less desirable bulk properties (e.g., thermal conductivity) when compared to W, its higher resilience to He+ ion-induced surface modification suggests that surface thermal and mechanical properties may not degrade as quickly in extreme fusion environments; this quality may be a redeeming factor for Ta as a plasma-facing material.

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“…Hence, it was proven that these plasma exposed surfaces do not only have a large surface area, but are also catalytically active. Kajita et al also studied the morphology development during plasma exposure for possible water splitting application using Fe and Ta bulk pellets recently [13]. For water splitting and many other 4 energy applications, however, thin films and not bulk material are used as electrodes due to costs, materials scarcity, and integration reasons.…”

Section: Introductionmentioning

confidence: 99%

Nanostructuring of iron thin films by high flux low energy helium plasma

et al. 2017

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High flux, low energy He plasma exposure is proven to nanostructure iron thin films over their entire thickness to a highly open structure with large surface area. From a large set of plasma exposure parameters, the ion flux, the surface temperature, and the plasma exposure time are found to be the most relevant parameters to process mechanically stable, nanostructured Fe thin films on brittle glass substrates. The nanostructure stays stable during oxidation. Different surface morphologies are found, depending on the location where the plasma plume interacts with the thin film. This method paves the way to a new direction in top down nanostructuring of thin films, which can be adopted for many functional materials in diverse applications that require a high ratio of active to projected surface area. KEYWORDSHigh ion flux plasma; nanostructure; iron thin film; catalytic applications 3

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Fuzzy nanostructure growth on Ta/Fe by He plasma irradiation

Cited by 51 publications

References 37 publications

Nanostructure Growth on Rhodium/Ruthenium by the Exposure to He Plasma

Nanostructure Growth on Rhodium/Ruthenium by the Exposure to He Plasma

Effect of high-flux, low-energy He+ ion irradiation on Ta as a plasma-facing material

Nanostructuring of iron thin films by high flux low energy helium plasma

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