Channeling of low-energy ions on hydrogen-covered single-crystal surfaces

Kolasinski, Robert; Bartelt, N. C.; Whaley, Josh A.; Felter, T. E.

doi:10.1103/physrevb.85.115422

Cited by 12 publications

(14 citation statements)

References 45 publications

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“…The saturation coverage case at 25°C depicted in Fig. 4(a) is nearly identical to our prior observations [3], with the same distinct hydrogen recoil patterns aligned along the h1 0 0i and h1 1 0i directions. This pattern provides clear evidence of adsorbed H residing in 2-fold (bridge) sites on the W(1 0 0) surface at 25°C at saturation coverage.…”

Section: Variation Of Binding Configuration As a Function Of Temperaturesupporting

confidence: 79%

“…Our previous analysis [3] did not reveal the definitive binding configuration at partial coverage. In the present study, the carefully controlled H dosing and systematic examination of coverage with temperature provide an opportunity for further analysis.…”

Section: Variation Of Binding Configuration As a Function Of Temperaturementioning

confidence: 94%

“…We refer the reader to several excellent reviews [1,2] for further details. In our prior work, we used LEIS and DRS to study the hydrogen binding configuration along open channels on the W(1 0 0) crystal plane [3]. While we were able to identify definitively two-fold bridge sites as the preferred binding site for complete coverage of the W surface with hydrogen, the details of the binding configuration at lower coverage were still unclear.…”

Section: Introductionmentioning

confidence: 96%

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Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

Kolasinski

Hammond

Whaley

et al. 2015

Journal of Nuclear Materials

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Article history:Available online xxxx a b s t r a c tIn this work, we apply low energy ion beam analysis to examine directly how the adsorbed hydrogen concentration and binding configuration on W(1 0 0) depend on temperature. We exposed the tungsten surface to fluxes of both atomic and molecular H and D. We then probed the H isotopes adsorbed along different crystal directions using 1-2 keV Ne + ions. At saturation coverage, H occupies two-fold bridge sites on W(1 0 0) at 25°C. The H coverage dramatically changes the behavior of channeled ions, as does reconstruction of the surface W atoms. For the exposure conditions examined here, we find that surface sites remain populated with H until the surface temperature reaches 200°C. After this point, we observe H rapidly desorbing until only a residual concentration remains at 450°C. Development of an efficient atomistic model that accurately reproduces the experimental ion energy spectra and azimuthal variation of recoiled H is underway.

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Section: Variation Of Binding Configuration As a Function Of Temperaturesupporting

confidence: 79%

Section: Variation Of Binding Configuration As a Function Of Temperaturementioning

confidence: 94%

Section: Introductionmentioning

confidence: 96%

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Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

Kolasinski

Hammond

Whaley

et al. 2015

Journal of Nuclear Materials

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“…From the experimental point of view, much effort has been put on Thermal Desorption Spectroscopy (TDS), also called Temperature Programmed Desorption (TPD) [12][13][14][15], and on ion beam analysis, such as Nuclear Reaction Analysis (NRA) [16][17][18][19] or Second Ions Mass Spectrometry (SIMS) [20]. Elastic Recoil Detection Analysis (ERDA) [21], Low Energy Ion Scattering (LEIS) and Direct Recoil Spectroscopy (DRS) [22][23][24] are also used, mostly to gain information on the surface properties. TDS can access global information related to the binding state of hydrogen in the bulk and on the surface, while ion beam analysis accesses local From the theoretical point of view, calculations and simulations have been carried out from the atomistic scales using Density Functional Theory (DFT) [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] and Molecular Dynamics (MD) [39][40][41][42][43], to the macroscopic scale using Kinetic Monte Carlo (KMC) [44][45][46][47] and Macroscopic Rate Equations (MRE) [15,[48][49][50]…”

Section: Introductionmentioning

confidence: 99%

Surface coverage dependent mechanisms for the absorption and desorption of hydrogen from the W(1 1 0) and W(1 0 0) surfaces: a density functional theory investigation

et al. 2019

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“…23 However, the gap between this accomplishment and the next step in developing the computational framework needed to simulate routinely ion scattering is much larger than simply moving these simulations to a cluster with many processors. The results depicted in the previous section included many simplifying assumptions specific to the W(100)+H(ads) system, some of which may not apply to more general systems.…”

Section: Future Modeling Pathwaymentioning

confidence: 99%

Fundamental hydrogen interactions with beryllium : a magnetic fusion perspective.

Wampler

Felter²,

Whaley³

et al. 2012

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Increasingly, basic models such as density functional theory and molecular dynamics are being used to simulate different aspects of hydrogen recycling from plasma facing materials [1,2]. These models provide valuable insight into hydrogen diffusion, trapping, and recombination from surfaces, but their validation relies on knowledge of the detailed behavior of hydrogen at an atomic scale. Despite being the first wall material for ITER, basic single crystal beryllium surfaces have been studied only sparsely from an experimental standpoint. In prior cases researchers used electron spectroscopy to examine surface reconstruction or adsorption kinetics during exposure to a hydrogen atmosphere [3]. While valuable, these approaches lack the ability to directly detect the positioning of hydrogen on the surface. Ion beam techniques, such as low energy ion scattering (LEIS) and direct recoil spectroscopy (DRS), are two of the only experimental approaches capable of providing this information.In this study, we applied both LEIS and DRS to examine how hydrogen binds to the Be(0001) surface. Our measurements were performed using an angle-resolved ion energy spectrometer (ARIES) to probe the surface with low energy ions (500 eV -3 keV He + and Ne + .)We were able to obtain a "scattering maps" of the crystal surface [4], providing insight on how low energy ions are focused along open surface channels. Once we completed a characterization of the clean surface, we dosed the sample with atomic hydrogen using a heated tungsten capillary. A distinct signal associated with adsorbed hydrogen emerged that was consistent with hydrogen residing between atom rows. To aid in the interpretation of the experimental results, we developed a computational model to simulate ion scattering at grazing incidence [5]. For this purpose, we incorporated a simplified surface model into the Kalypso molecular dynamics code [6]. This approach allowed us to understand how the incident ions interacted with the surface hydrogen, providing confirmation of the preferred binding site.[1] A. Allouche, Phys. Rev. B, 78 (2008) 085429.[2] R. Stumpf and P

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Channeling of low-energy ions on hydrogen-covered single-crystal surfaces

Cited by 12 publications

References 45 publications

Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

Analysis of hydrogen adsorption and surface binding configuration on tungsten using direct recoil spectrometry

Surface coverage dependent mechanisms for the absorption and desorption of hydrogen from the W(1 1 0) and W(1 0 0) surfaces: a density functional theory investigation

Fundamental hydrogen interactions with beryllium : a magnetic fusion perspective.

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