Erosion and dust formation of graphite materials under low-energy and high-flux atomic hydrogen irradiation

Takeguchi, Yuji; Kyo, Masaaki; Uesugi, Yoshihiko; Tanaka, Yasunori; Masuzaki, S.

doi:10.1088/0031-8949/2009/t138/014056

Cited by 5 publications

(3 citation statements)

References 6 publications

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“…The graphite samples temperature (1000-1200 K) was well above the peak temperature for chemical erosion. If the temperature of the diamond samples was close to the peak temperature, the difference between graphite and diamond would be much larger than that reported here, which would be consistent with recent measurements of the chemical erosion yield of diamond coated graphite by low temperature plasmas (∼1 eV) [15]. Table 1 shows the measured erosion of ATJ graphite, NCD and boron-doped MCD (0.1% B) after exposure to deuterium neutrals reflected from a tungsten target.…”

Section: Erosion Of Diamondsupporting

confidence: 88%

Interactions of diamond surfaces with fusion relevant plasmas

et al. 2009

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The outstanding thermal properties of diamond and its low reactivity towards hydrogen may make it an attractive plasma-facing material for fusion and calls for a proper evaluation of its behaviour under exposure to fusion-relevant plasma conditions. Micro and nanocrystalline diamond layers, deposited on Mo and Si substrates by hot filament chemical vapour deposition (CVD), have been exposed both in tokamaks and in linear plasma devices to measure the erosion rate of diamond and study the modification of the surface properties induced by particle bombardment. Experiments in Pilot-PSI and PISCES-B have shown that the sputtering yield of diamond (both physical and chemical) was a factor of 2 lower than that of graphite. Exposure to detached plasma conditions in the DIII-D tokamak have evidenced a strong resistance of diamond against erosion under those conditions.

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Section: Erosion Of Diamondsupporting

confidence: 88%

Interactions of diamond surfaces with fusion relevant plasmas

et al. 2009

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“…Similar structures were formed previously in linear plasma simulator experiments, 42,43 using high-pressure inductively coupled plasmas, 44 helicon-wave excited discharge, 45,63 and even in the tokamak environment. 46,47 Furthermore, analogous structures were observed in PECVD processing, for instance, during early stages of ultrananocrystalline diamond growth 48,49 or during growth of carbon nanowalls.…”

Section: B Location and Structure Of The Redepositssupporting

confidence: 78%

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

Bystrov

Vegt

Temmerman

et al. 2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Fine-grain graphite samples were exposed to high density low temperature (ne∼1020 m−3, Te∼1 eV) hydrogen plasmas in the Pilot-PSI linear plasma generator. Redeposition of eroded carbon is so strong that no external precursor gas injection is necessary for deposits to form on the exposed surface during the bombardment. In fact, up to 90% of carbon is redeposited, most noticeably in the region of the highest particle flux. The redeposits appear in the form of carbon microparticles of various sizes and structures. Discharge parameters influence the efficiency of the redeposition processes and the particle growth rate. Under favorable conditions, the growth rate reaches 0.15 μm/s. The authors used high resolution scanning electron microscopy and transmission electron microscopy to study the particle growth mode. The columnar structure of some of the large particles points toward surface growth, while observation of the spherical carbon nanoparticles indicates growth in the plasma phase. Multiple nanoparticles can agglomerate and form bigger particles. The spherical shape of the agglomerates suggests that nanoparticles coalesce in the gas phase. The erosion and redeposition patterns on the samples are likely determined by the gradients in plasma flux density and surface temperature across the surface.

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“…In the former, radicals created by plasma dissociation of a reactive gas interact with the substrate surface to create new, weakly-bound chemical groups. Chemical etching by plasma-generated hydrogen atoms has been thoroughly studied in carbonaceous materials for nuclear fusion applications since graphite is a good candidate for the plasmafacing components [16][17][18][19][20]. In physical etching, the atom ejection is obtained through knock-on collisions with the positive ions impinging onto the surface following their acceleration in the plasma sheath.…”

Section: Introductionmentioning

confidence: 99%

Plasma–graphene interactions: combined effects of positive ions, vacuum-ultraviolet photons, and metastable species

Vinchon¹,

Glad²,

Bigras³

et al. 2021

J. Phys. D: Appl. Phys.

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This study compares the impact of different plasma environments on the damage formation dynamics of polycrystalline monolayer graphene films on SiO2/Si substrates and investigates the combined effects often observed in low-pressure argon plasmas. After careful characterization of the discharge properties by Langmuir probes and optical absorption spectroscopy, three operating conditions were selected to promote graphene irradiation by either positive ions, metastable species, or vacuum-ultraviolet (VUV) photons. In all cases, hyperspectral Raman imaging of graphene reveals plasma-induced damage. In addition, defect generation is systematically slower at grain boundaries (GBs) than within the grains, a behavior ascribed to a preferential self-healing of plasma-induced defects at GBs. The evolution of selected Raman band parameters is also correlated with the energy fluence provided to the graphene lattice by very-low-energy ions. From such correlation, it is shown that the presence of VUV photons enhances the defect formation dynamics through additional energy transfer. On the other hand, the presence of metastable species first impedes the defect generation and then promotes it for higher lattice disorder. While this impediment can be linked to an enhanced defect migration and self-healing at nanocrystallite boundaries in graphene, such effect vanishes in more heavily-damaged films.

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Erosion and dust formation of graphite materials under low-energy and high-flux atomic hydrogen irradiation

Cited by 5 publications

References 6 publications

Interactions of diamond surfaces with fusion relevant plasmas

Interactions of diamond surfaces with fusion relevant plasmas

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment

Plasma–graphene interactions: combined effects of positive ions, vacuum-ultraviolet photons, and metastable species

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