In situ work function measurements of W, WO₃ nanostructured surfaces

Surface nanostructuring enables the fabrication of materials with highly desirable properties. Nanostructured tungsten surfaces have potential applications in solar water splitting. Exposing a polished tungsten surface to helium plasma induces various surface morphological changes. Depending on the helium ion energy, temperature, and fluence, helium clusters, helium bubbles and foam-like nanostructures develop on the tungsten surface. In this study, tungsten foam-like nanostructures were formed and/or oxidised, and then examined using X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) without breaking the vacuum. The chemical state of nanostructured W or WO3 was not modified in comparison to the pristine one. However, measuring the line width of the emitted electrons from the onset of the secondary electrons up to the Fermi edge and subtracting value from the incident photon energy, the work function acquired in situ by UPS for a nanostructured W surface increased by 0.9 eV in comparison to the pristine one. Helium ions effectively eliminated field emission sites via sputtering/implantation and thereby increased the work function. No change in work function was measured for WO3-pristine and its fuzz: the oxidation hindered the effect of helium. In contrast to the W-fuzz sample, no helium bubbles were identified in WO3-fuzz, as helium diffused out during oxidation

Enhanced growth of large-scale nanostructures with metallic ion precipitation in helium plasmas

Abstract Helium plasma irradiation on metal surfaces leads to the formation of metallic fuzzy nanostructures accompanied by the growth of helium bubbles in metals. The mechanism of the growth process, its impact for fusion devices, and potential application have been explored. Here we show enhanced growth of large-scale fuzz by precipitating additional metallic particles during helium plasma irradiation. The growth rate of the fuzzy structures became orders of magnitude greater than conventional fuzz growth; in an hour of irradiation, 1 mm-thick visible tungsten and molybdenum fuzzy fur structures covered a tungsten metal substrate. Additional precipitation of metallic ions breaks the bottleneck diffusion process; moreover, further acceleration in the growth rate could have occurred if the electric sheath shape was influenced by the grown structure and the electric field that formed around the structure started collecting ions

Valence band behaviour of zirconium oxide, Photoelectron and Auger spectroscopy study

Abstract In this study X-ray Photoelectron Spectroscopy and Ultraviolet Photoelectron Spectroscopy were combined to investigate the effect of oxygen incorporation on the valence band behaviour of ZrO x . The Auger transitions involving valence bands are found to mimic the self-folded density of state measured using Ultraviolet Photoelectron Spectroscopy. The valence band once constructed in a sub-oxide form, stays at a fixed energy position despite the change in the stoichiometry. This behaviour is found to be useful in setting a reference for X-ray Photoelectron Spectroscopy charge correction. The results of the charged corrected spectra were compared to other methods and found to be in great agreement. Finally, a correlation between the core-level binding energy and the structural property of ZrO x is given