The thermal conductivity of ${\mathrm{Ge}}_2{\mathrm{Sb}}_2{\mathrm{Te}}_5$ (GST) layers, as well as the thermal boundary resistance at the interface between the GST and amorphous $\mathrm{Si}{\mathrm{O}}_2$ , was measured using a photothermal radiometry experiment. The two phase changes in the ${\mathrm{Ge}}_2{\mathrm{Sb}}_2{\mathrm{Te}}_5$ were retrieved, starting from the amorphous and sweeping to the face centered cubic (fcc) crystalline state at $130°\mathrm{C}$ and then to the hexagonal crystalline phase (hcp) at $310°\mathrm{C}$ . The thermal conductivity resulted to be constant in the amorphous phase, whereas it evolved between the two crystalline states. The thermal boundary resistance at the $\mathrm{GST}\text{-}\mathrm{Si}{\mathrm{O}}_2$ interface was estimated to be higher for the hcp phase than for the amorphous and fcc ones.

The structural defects in two-dimensional transition metal dichalcogenides, including point defects, dislocations and grain boundaries, are scarcely considered regarding their potential to manipulate the electrical and optical properties of this class of materials, notwithstanding the significant advances already made. Indeed, impurities and vacancies may influence the exciton population, create disorder-induced localization, as well as modify the electrical behaviour of the material. Here we report on the experimental evidence, confirmed by ab initio calculations, that sulfur vacancies give rise to a novel near-infrared emission peak around 0.75 eV in exfoliated MoS₂ flakes. In addition, we demonstrate an excess of sulfur vacancies at the flake’s edges by means of cathodoluminescence mapping, aberration-corrected transmission electron microscopy imaging and electron energy loss analyses. Moreover, we show that ripplocations, extended line defects peculiar to this material, broaden and redshift the MoS₂ indirect bandgap emission.

Large-scale integration of MoS ₂ in electronic devices requires the development of reliable and cost-effective deposition processes, leading to uniform MoS ₂ layers on a wafer scale. Here we report on the detailed study of the heterogeneous vapor–solid reaction between a pre-deposited molybdenum solid film and sulfur vapor, thus resulting in a controlled growth of MoS ₂ films onto SiO ₂ /Si substrates with a tunable thickness and cm ² -scale uniformity. Based on Raman spectroscopy and photoluminescence, we show that the degree of crystallinity in the MoS ₂ layers is dictated by the deposition temperature and thickness. In particular, the MoS ₂ structural disorder observed at low temperature (<750 °C) and low thickness (two layers) evolves to a more ordered crystalline structure at high temperature (1000 °C) and high thickness (four layers). From an atomic force microscopy investigation prior to and after sulfurization, this parametrical dependence is associated with the inherent granularity of the MoS ₂ nanosheet that is inherited by the pristine morphology of the pre-deposited Mo film. This work paves the way to a closer control of the synthesis of wafer-scale and atomically thin MoS ₂ , potentially extendable to other transition metal dichalcogenides and hence targeting massive and high-volume production for electronic device manufacturing.

Spin‐charge interconversion phenomena at the interface between magnetic materials and topological insulators (TIs) are attracting enormous interest in the research effort toward the development of fast and ultra‐low power devices for future information and communication technology. A large spin‐to‐charge (S2C) conversion efficiency in Au/Co/Au/Sb₂Te₃/Si(111) heterostructures based on Sb₂Te₃ TIs grown by metal–organic chemical vapor deposition on 4″ Si(111) substrates is reported. By conducting room temperature spin pumping ferromagnetic resonance, a 250% enhanced charge current due to spin pumping in the Sb₂Te₃‐containing system is measured when compared to the reference Au/Co/Au/Si(111). The corresponding inverse Edelstein effect length λ_IEE ranges from 0.28 to 0.61 nm, depending on the adopted methodological analysis, with the upper value being so far the largest observed for the second generation of 3D chalcogenide‐based TIs. These results open the path toward the use of chemical methods to produce TIs on large area Si substrates and characterized by highly performing S2C conversion, thus marking a milestone toward future technology‐transfer.