We present a study on the growth and characterization of high-quality single-layer MoS ₂ with a single orientation, i.e. without the presence of mirror domains. This single orientation of the MoS ₂ layer is established by means of x-ray photoelectron diffraction. The high quality is evidenced by combining scanning tunneling microscopy with x-ray photoelectron spectroscopy measurements. Spin- and angle-resolved photoemission experiments performed on the sample revealed complete spin-polarization of the valence band states near the K and -K points of the Brillouin zone. These findings open up the possibility to exploit the spin and valley degrees of freedom for encoding and processing information in devices that are based on epitaxially grown materials.

An order-disorder transition of oxygen adsorbed on the Rh(100) surface has been studied by means of spot profile analysis low-energy electron diffraction (SPA-LEED). The $p(2\mathrm{}\times 2)\to c(2\mathrm{}\times 2)$ transition has been found to belong to the Ising universality class, with critical temperature 450±5 K. Careful consideration of the profile broadening allows the determination of the type of defect implicated in the disordering process, and it is defined in terms of a surface Burgers vector. Furthermore, the thermodynamic parameters allow an energy/unit length to be associated with these defects.

A real-time XPS investigation of single- and multi-layer graphene growth on Ir (111).

Size-selected iron oxide nanoclusters are outstanding candidates for technological-oriented applications due to their high efficiency-to-cost ratio. However, despite many theoretical studies, experimental works on their oxidation mechanism are still limited to gas-phase clusters. Herein we investigate the oxidation of graphene-supported size-selected Fe_nclusters by means of high-resolution X-ray Photoelectron Spectroscopy. We show a dependency of the core electron Fe 2p_3/2binding energy of metallic and oxidized clusters on the cluster size. Binding energies are also linked to chemical reactivity through the asymmetry parameter which is related to electron density of states at the Fermi energy. Upon oxidation, iron atoms in clusters reach the oxidation state Fe(II) and the absence of other oxidation states indicates a Fe-to-O ratio close to 1:1, in agreement with previous theoretical calculations and gas-phase experiments. Such knowledge can provide a basis for a better understanding of the behavior of iron oxide nanoclusters as supported catalysts.