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Single-atom catalysts often show exceptionally high performance per metal loading.

Silicon nanoparticles (SiNPs) have been explored intensively for their use in applications requiring efficient fluorescence for LEDs, lasers, displays, photovoltaic spectral-shifting filters, and biomedical applications. High radiative rates are essential for such applications, and theoretically these could be achieved via quantum confinement and/or straining. Wet-chemical methods used to synthesize SiNPs are under scrutiny because of reported contamination by fluorescent carbon species. To develop a cleaner method, we utilize a specially designed attritor type high-energy ball-mill and use a high-purity (99.999%) Si microparticle precursor. The mechanochemical process is used under a continuous nitrogen gas atmosphere to avoid oxidation of the particles. We confirm the presence of quantum-confined NPs (

The phase and composition of several transition metal silicides are challenging to identify with common surface analysis techniques such as X-ray photoelectron spectroscopy (XPS). While silicide formation is concomitant with a distinct change in electronic structure, only minute changes in the main spectral features are observed for example for the family of Ru silicides. Here, the authors combine XPS, grazing-incidence X-ray diffraction, and density functional theory calculations to demonstrate that the characteristic excitation energies of plasmons in Ru and its silicides are a sensitive and easily accessible descriptor that reflects the change in electronic structure upon the formation of specific silicides in the XPS spectra. Electron energy loss satellites are reported to shift by more than 4 eV upon the formation of Ru silicide, by 1.1 eV between RuSi and Ru2Si3 and by 1.9 eV across the measured range of silicide layers, making these changes accessible even for basic experimental equipment. In the context of literature on metal silicides and electron energy loss spectroscopy, this approach is considered promising as a general pathway to enhance the chemical sensitivity of surface spectroscopy methods.

Pathways to tune the electronic, chemical, mechanical, and optical properties of solids without modifying their composition represent a new paradigm in the design of functional and sustainable materials. The level of structural disorder - from perfectly crystalline to fully amorphous – for example, induces remarkable changes in material properties. Typically, disorder is introduced by altering the composition of a material, adding to the misconception that these two properties cannot be decoupled. Here, we demonstrate that striking differences in the optical, electronic, and corrosion properties of CuZr are achieved by deliberately and reproducibly engineering the level of structural disorder in pulsed laser deposited thin films of a constant composition. This approach allows tuning the structure of CuZr from polycrystalline to fully amorphous, switching the nature of charge transport from metallic to semiconductor-like, the optical properties in the visible regime from opaque to transparent, and the corrosion behavior in air from mixed oxidation to the formation of a protective Zr oxide overlayer. Our results highlight the tunability of structural disorder in alloys and its remarkable effect on material properties, providing the opportunity to design sustainable functional materials based on customizing properties beyond their composition.

Microscopy and diffraction measurements are presented of ultrathin binary alloy films of ruthenium and molybdenum that are obtained by standard sputter deposition. For compositions close to Ru50Mo50, we find the films to be amorphous. The amorphicity of the films is accompanied by a significant reduction of the roughness with respect to the roughness of equally thick films of either ruthenium or molybdenum. We ascribe this to the absence of the grain structure that is characteristic of the polycrystalline films of the separate elements.

Free-standing layers of nanoscale thickness are essential in numerous applications but challenging to fabricate for all but a small selection of materials. We report a versatile, chemical-free pathway of exfoliating centimeter-sized free-standing nanolayers from Si(100) with native oxide based on the spontaneous delamination of thin Ru and Ru-based films upon annealing at temperatures as low as 400 °C. Combining results from X-ray photoelectron spectroscopy (XPS), and transmission and scanning electron microscopy (TEM, SEM), we identify that the element Ru, a thin SiO2 layer, and the Si(100) substrate are essential ingredients for the delamination and propose a stress-based mechanism to explain the effect. The diffusion of Si into the layer upon annealing leads to the formation of a Ru-Si compound at the thin-film side of the Ru/Si(100) interface and pyramidal cavities in the Si(100) substrate. Moreover, the uptake of Si results in an increase in layer thickness and the buildup of in-plane compressive stress, which is reduced by local buckling and finally by the separation of the full layer from the substrate at the SiO2-Si(100) interface. The use of a thin Ru-buffer layer allows us to apply this delamination process to produce free-standing nanolayers of Mo and HfMoNbTiZr in this simple, chemical-free, and vacuum-compatible manner. These results indicate the potential of the reported effect for the fabrication of free-standing layers using a wide range of compositions, deposition techniques, and growth conditions below the onset temperature of delamination.

We report on the reproducible surface topological electron states in Bi2Se3 topological insulator thin films when epitaxially grown by Pulsed Laser Deposition (PLD) on (0 0 1)-oriented SrTiO3 (STO) perovskite substrates. Bi2Se3 has been reproducibly grown with single (0 0 1)-orientation and low surface roughness as controlled by ex-situ X-ray diffraction and in situ scanning tunnel microscopy and low-energy electron diffraction. Finally, in situ synchrotron radiation angle-resolved photo-emission spectroscopy measurements show a single Dirac cone and Dirac point at E B ∼ 0.38 eV located in the center of the Brillouin zone likewise found from exfoliated single-crystals. These results demonstrate that the topological surface electron properties of PLD-grown Bi2Se3 thin films grown on (0 0 1)-oriented STO substrates open new perspectives for applications of multi-layered materials based on oxide perovskites.

Two-dimensional (2D) metallic states induced by oxygen vacancies (${V}_{O}\mathrm{s}$) at oxide surfaces and interfaces provide opportunities for the development of advanced applications, but the ability to control the behavior of these states is still limited. We used angle resolved photoelectron spectroscopy combined with density-functional theory (DFT) to study the reactivity of ${V}_{O}$-induced states at the (001) surface of anatase ${\mathrm{TiO}}_{2}$, where both 2D metallic and deeper lying in-gap states (IGs) are observed. The 2D and IG states exhibit remarkably different evolutions when the surface is exposed to molecular ${\mathrm{O}}_{2}$: while IGs are almost completely quenched, the metallic states are only weakly affected. DFT calculations indeed show that the IGs originate from surface ${V}_{O}\mathrm{s}$ and remain localized at the surface, where they can promptly react with ${\mathrm{O}}_{2}$. In contrast, the metallic states originate from subsurface vacancies whose migration to the surface for recombination with ${\mathrm{O}}_{2}$ is kinetically hindered on anatase ${\mathrm{TiO}}_{2}$ (001), thus making them much less sensitive to oxygen dosing.

The semiconductor industry plans to keep fabricating integrated circuits, progressively decreasing there features size, by employing extreme ultraviolet lithography (EUVL). With this method, new designs and concepts for photoresist materials need to be conceived. In this work, we explore an alternative concept to the classic photoresist material by using an organic self-assembled monolayer (SAM) on a gold substrate. The monolayer, composed of a richly fluorinated thiol sensitive to low-energy electrons, is adsorbed on the Au substrate which acts as main EUV-absorber and as the source of photoelectrons and secondary electrons. We investigate the stability of the SAM adsorbed on gold towards EUV radiation by means of in-situ photoelectron spectroscopy. The photoelectron spectra indicate that the monolayer attenuates a significant amount of primary electrons generated in the gold layer. The spectral evolution upon EUV irradiation indicates that the SAM loses a significant amount of its initial fluorine content (ca. 40% at 200 mJ/cm2). We attribute these chemical changes mostly to the interaction with the electrons generated in the thiol/Au system.