Tungsten oxide thin film bombarded with a low energy He ion beam: evidence for a reduced erosion and W enrichment

Abstract

Nanocrystalline tungsten oxide (WO 3) thin films synthesized by thermal oxidation of tungsten substrates were exposed to low energy helium ions (energy: 80 eV; flux: 1.4-1.7×10 20 m-2 s-1) at room temperature and at 673 K. The structure and morphology changes of the oxide were studied using Raman spectroscopy and electron microscopy. Due to the low ion energy, no erosion is observed at room temperature. On the contrary, at 673 K, a colour change is observed and a significant erosion is measured (~ 70 nm for a fluence of ~ 4×10 21 m-2) due to a synergetic effect between ion bombardment and heating. We show that erosion processes and structural changes strongly depend on the ion fluence and in particular the higher the fluence, the lower the erosion yield, most likely due to oxygen depletion in the oxide near-surface layers.

Post-mortem analysis of tungsten plasma facing components in tokamaks: Raman microscopy measurements on compact, porous oxide and nitride films and nanoparticles

“…The W-N bonds could be related to the very weak signal around 400 cm -1 . The spectrum from the cWON (37,16) sample is totally flat in the same spectral region. In this case, the absence of bands whereas W-N bonds are present in cWON (37,16) can be due to some quantum-selection rules related to the structure during the Raman scattering process, whereas the presence of defects (like oxygen and nitrogen, grain boundaries due to small crystallite size,…) can break the related quantum selection rules, leading to the presence of these bands.…”

“…The spectrum from the cWON (37,16) sample is totally flat in the same spectral region. In this case, the absence of bands whereas W-N bonds are present in cWON (37,16) can be due to some quantum-selection rules related to the structure during the Raman scattering process, whereas the presence of defects (like oxygen and nitrogen, grain boundaries due to small crystallite size,…) can break the related quantum selection rules, leading to the presence of these bands. The lack of signal intensity corresponding to W-O bonds is different here, possibly due to the stability of the W-N bonds that hinder the formation of W-O bonds during the deposition process of the film.…”

“…An additional shift of roughly 0.5 eV has been reported in the literature [53], possibly due to nano structuration and phase changes; we do not discuss in this publication. The XPS spectrum of d-WO 3 , extracted from [37], is composed of two peaks related to WO [65].…”

“…XPS and Raman spectra of d-WO 3 , NP, pWO, cWO, cW and cWN samples. XPS spectra of (a) pWO (60, 2.5), cWO (25,2) and d-WO 3 (the latter from [37]) and (b) cWN(0, 20) and cW. (c) Raman spectra.…”

Tuning the Electronic Structure of Tungsten Oxide for Enhanced Hydrogen Evolution Reaction in Alkaline Electrolyte

“…According to the literature, the other four peaks represented W 5+ 4f 7/2 (34.7 eV), W 5+ 4f 5/2 (36.8 eV), W 6+ 4f 7/2 (35.9 eV), and W 6+ 4f 5/2 (38.0 eV), resulting from WO 2.72 (surface oxidation). Moreover, the two peaks at lower energies (31.6 and 33.7 eV) were assigned to metallic W 4f 7/2 and W 4f 5/2 , respectively [40–42] . Compared with Ni 2+ , the binding energy shift W ions is insignificant and can be ignored.…”