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In this paper, an experimental measurement of the diffusion constant of hydrogen in ruthenium is presented. By using a hydrogen indicative Y layer, placed under the Ru layer, the hydrogen flux through Ru was obtained by measuring the optical changes in the Y layer. We use optical transmission measurements to obtain the hydrogenation rate of Y in a temperature range from room temperature to 100 °C. We show that the measured hydrogenation rate is limited mainly by the hydrogen diffusion in Ru. These measurements were used to estimate the diffusion coefficient, D, and activation energy of hydrogen diffusion in Ru thin films to be D = 5.9 × 10−14 m2/s ∙ exp (-0.33 eV/kBτ), with kB the Boltzmann constant and τ the temperature.

Transition metals used in semiconductor, photolithography and fusion applications interact with low energy oxygen ions. Understanding erosion, the nature of the formed oxide and depth of oxygen transport is necessary in mitigating unexpected performance of sensors, optics or plasma facing components. Oxide formation is governed by both the ion–target combination and the incident ion energy. We study the interaction of the transition metals molybdenum, ruthenium, palladium and tungsten, with oxygen ions in the energy region of 50–500 eV. Near-threshold sputtering of metals was experimentally measured and compared to predictions by the Monte Carlo code TRIDYN. Compositional changes and oxide thicknesses following sputtering were measured using Angle resolved X-ray photoelectron spectroscopy and subsequently compared to limiting oxide formed by atomic oxygen exposures. Sputter yields in some cases (ruthenium) were found to be sensitive to ion beam impurities such as ozone ( 1% of background gas) leading to chemical sputtering. Ion induced oxide thicknesses (for molybdenum and tungsten) were found to be larger than those predicted by ballistic transport where sputtering is balanced by implantation. It is hypothesized that radiation enhanced diffusion of free oxygen leads to thicker oxide films at low ion energies.

In this work, a technique for hydrogen diffusion measurements through thin films is proposed and demonstrated. A yttrium film, which changes its refractive index upon hydrogen absorption, is used as an optical sensor to detect hydrogen. The yttrium sensor is coated with a thin (up to 12 nm) layer of test material and exposed to atomic hydrogen. To ensure that the calculated diffusion constant is not artificially changed by surfaces processes, the test layer is coated with palladium. Hydrogen diffusion through test layers of Si, Al, Ag, Ru, Mo, Al2O3 and SiO2 were measured and compared with existing data. The hydrogenation time (time to form YH2) was found to exponentially scale with the enthalpy of hydrogen solution in the test material. Comparison between measured diffusion coefficients for different film thicknesses, as well as previously reported results, highlights the strong dependence of the diffusion constant on sample fabrication conditions, and hydrogen exposure conditions. It is concluded that diffusion through thin films can be reliably compared only when specimen form and exposure conditions are the same. The relevance of this study for applications is discussed.

X-ray W/B multilayer mirrors with a period of 2.5 nm were deposited by dc magnetron sputtering and studied in comparison with W/Si multilayer systems of the same period. Transmission electron microscopy, grazing incidence X-Ray reflectivity, and x-ray photoelectron spectroscopy analysis revealed that the layer quality and interfaces of the W/B multilayers are not better than those of the W/Si multilayers. Strong intermixing between W and B is present, which leads to compound formation with little or no pure W left after the interaction: an optically unfavorable boride formation and an increased roughness result in a reduced reflectivity. The deposited W/B multilayer mirrors showed a reflectivity of 34.5% at 0.84 nm and angle of incidence 9.7°, compared to 40% obtained for W/Si multilayers. Ion polishing applied on the boron layers did not result in improvements of the reflectivity.

Transition metal surfaces exposed to low-energy reactive ions undergo dynamic changes in composition and density due to implantation and compound formation. We report measurements of nitrogen ion induced sputter yields for transition metals relevant to fusion and optics applications. Thin films of molybdenum, ruthenium, palladium and tungsten are bombarded by nitrogen ions of kinetic energies in the range of 50–500 eV at steady state fluences (1 × 10 18 ions / cm 2 ). Measured sputter yields are explained through energy and momentum transfer under the binary collision approximation using the Monte Carlo code TRIDYN. X-ray Photoelectron spectroscopy (XPS) studies showed the nitrogen content in the films at the end of ion exposure is independent of incoming ion energy. This occurs due to competing implantation and preferential surface nitrogen sputtering processes within the XPS probing depth. All metals investigated showed evidence of a nitride formed due to energetic nitrogen impact. The combination of XPS and TRIDYN simulations were applied to extract effective reaction cross-sections for each metal.

Freestanding silicon nitride membranes with thicknesses down to a few tens of nanometers find use as TEM windows or soft X-ray spectral purity filters. As the thickness of a membrane decreases, emissivity vanishes, which limits radiative heat emission and resistance to heat loads. We show that thin metal layers with thicknesses in the order of 1 nm enhance the emissivity of thin membranes by two to three orders of magnitude close to the theoretical limit of 0.5. This considerably increases thermal load capacity of membranes in vacuum environments. Our experimental results are in line with classical theory in which we adapt thickness dependent scattering terms in the Drude and Lorentz oscillators., Comment: 5 pages, 5 figures

A Particle-in-Cell Monte Carlo model is used to simulate extreme ultraviolet driven plasma. In an extreme ultraviolet lithography tool, photons of a pulsed discharge source will ionize a low pressure argon gas by photoionization. Together with the photoelectric effect, this results in a strongly time dependent and low density plasma, which is potentially dangerous to the optical elements, the collector in particular. Plasma sheaths will develop and ions are accelerated towards the collector, which might lead to sputtering. A spherical geometry is used to study the plasma between the point source and collector. Simulations are performed to study the in.uence of background pressure and source intensity on the damage to the collector by sputtering.