We report the effects of carbon incorporation on the structural and magnetic properties of epitaxial Mn 5 Ge 3 C x films grown on Ge(111) by the solid phase epitaxy method. This variation of molecular beam epitaxy favors the diffusion process of carbon atoms. We show that up to a carbon molar concentration x of ∼0.6-0.7, the atoms are incorporated in the interstitial sites of the Mn 5 Ge 3 lattice. Such a process results in a linear increase of the Curie temperature T C of the alloy, which can reach a value as high as ∼430 K [T C ≈ 460 K at M(T C ) = 0]. Above this carbon content, T C is found to decrease. Structural characterizations reveal that Mn 5 Ge 3 C x films are in perfect epitaxy when x 0.6, whereas cluster formation in the grown layers is detected above that threshold. The clusters can be attributed to manganese carbide (MnC) compounds which are formed when the carbon content exceeds the saturation value of 0.6 by consuming previously deposited carbon. Theoretical calculations accurately reproduce the main trend of T C variation as well as the cluster formation for x larger than the saturation content. In addition, we also show that after post-thermal annealing, the carbon-doped Mn 5 Ge 3 C x alloys remain magnetically and structurally stable up to a temperature as high as 850 • C. The results are very promising for integrating Mn 5 Ge 3 C x into ferromagnetic-semiconductor heterostructures, the ultimate goal being the realization of spintronic devices.

We have investigated the electronic properties of two-dimensional (2D) transition metal dichalcogenides (TMDs), namely trilayer WSe 2 and monolayer MoSe 2 , deposited on epitaxial graphene on silicon carbide, by using scanning tunneling microscopy and spectroscopy (STM/STS) in ultra-high vacuum. Depending on the number of graphene layers below the TMD flakes, we identified variations in the electronic dI/dV(V) spectra measured by the STM tip: the most salient feature is a rigid shift of the TMD spectra (i.e. of the different band onset positions) towards occupied states by about 120 mV when passing from bilayer to monolayer underlying graphene. Since both graphene phases are metallic and present a work function difference in the same energy range, our measurements point towards the absence of Fermi-level pinning for such van der Waals 2D TMD/ Metal heterojunctions, following the prediction of the Schottky-Mott model. PAPEROriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.