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

Abstract

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.

Predictive Atomistic Model for Hydrogen Adsorption on Metal Surfaces: Comparison with Low-Energy Ion Beam Analysis on Tungsten

“…Regarding the W(100) surface, additional configurations were also computed as compared to is around -0.8eV as the results of the well-known surface reconstruction [27][28][29][30]23 . Then the trend is similar to the one of the W(110) surface with 𝐸 𝑎𝑑 𝑛+1 around -0.65eV up to coverage 𝜃 = 2.00, which is the minimum of the curve.…”

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

“…Previous DFT [24] and experimental [68,69,[22][23][24] A c c e p t e d M a n u s c r i p t Table 1: Embedding and solution energies as defined in equation 1 and 2. The Zj refer to the location of the interstitial sites below the W(110) surface.…”

“…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]…”

A density functional theory based thermodynamic model of hydrogen coverage on the W(110) surface

“…Thus it is of high important to understand hydrogen-tungsten surface interactions at a fundamental level. Several experimental studies have been conducted on single crystalline samples of tungsten including TDS [8][9][10], LIES, DRS [11], LEED [3,4,12,13], and surface reflectance spectroscopy [14] measurements. Of these techniques, LEED and LIES/DRS are best able to probe atomic-scale phenomena on the surface.…”

“…of plots of Δ ( , ) vs. Θ at different temperatures, all with = 5.5 × 10 −5 Pa. This pressure was chosen since it is within the range of surface analysis experiments[3,11]. Focusing on the minimum value of Δ ( , ) with respect to the various isotherms shown inFigure 3a,we can see how the model yields the expected coverages plotted in…”