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Mn5Ge3 compound, with its room-temperature ferromagnetism and possibility to epitaxially grow on Ge, acts as a potential spin injector into group-IV semiconductors. However, the realization of Ge/Mn5Ge3 multilayers is highly hampered by Mn segregation toward the Ge growing surface. Here, we show that adsorption of some monolayers of carbon on top of the Mn5Ge3 surface prior to Ge deposition allows to greatly reduce Mn segregation. In addition, a fraction of deposited carbon can diffuse down to the underneath Mn5Ge3 layers, resulting in an enhancement of the Curie temperature up to ∼360 K. The obtained results will be discussed in terms of the formation of a diffusion barrier by filling interstitial sites of Mn5Ge3 by carbon.

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The effect of solute segregation on strain localization in nanocrystalline thin films: Dislocation glide vs. grainboundary mediated plasticity Lattice and grain-boundary diffusions of boron atoms in BaSi2 epitaxial films on Si(111) J. Appl. Phys. 113, 053511 (2013); 10.1063/1.4790597 Effect of Cu and Ag solute segregation on βSn grain boundary diffusivityThe diffusion coefficient of As in 260 nm thick polycrystalline Ni 2 Si layers has been measured both in grains and in grain boundaries ͑GBs͒. As was implanted in Ni 2 Si layers prepared via the reaction between a Si layer and a Ni layer deposited by magnetron sputtering on a ͑100͒ Si substrate covered with a SiO 2 film. The As concentration profiles in the samples were measured using secondary ion mass spectroscopy before and after annealing ͑400-700°C͒. The diffusion coefficients in the grains and the GBs have been determined using two-dimensional finite element simulations based on the Fisher model geometry. For short time annealing ͑1 h͒ and temperatures lower than 600°C, lattice diffusion has not been observed. However, GB diffusion was evidenced for temperatures as low as 400°C. For higher thermal budgets, As diffuses simultaneously in the volume of the grains and in the GBs. Lattice diffusion is characterized by a pre-exponential factor D 0v ϳ 1.5 ϫ 10 −1 cm 2 s −1 and an activation energy Q v ϳ 2.72Ϯ 0.10 eV. In the case of GB diffusion, the triple product of the As segregation coefficient ͑s͒, the GB width ͑␦͒, and the diffusion coefficient ͑D GB ͒ is found to be s␦D GB = 9.0ϫ 10 −3 exp͑−3.07Ϯ 0.15 eV/ kT͒ cm 3 s −1 . Various types of simulations were used in order to support the discussion of the results.

A mineral (celadonite, kaolinite) nanometer-thick particle deposited on a flat carbon film or at the apex of a carbon fiber provides electron emission at low applied fields. Voltage and time dependences of the emission intensity are studied, and a model of the underlying mechanism is proposed. An electron point source providing emission from a single particle is built and characterized.

International audienceUsing scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy, and low energy electron diffraction, we have studied the growth of Mg deposited on Si(100)-(2 x 1). Coverage from 0.05 monolayer (ML) to 3 ML was investigated at room temperature. The growth mode of the magnesium is a two steps process. At very low coverage, there is formation of an amorphous ultrathin silicide layer with a band gap of 0.74 eV, followed by a layer-by-layer growth of Mg on top of this silicide layer. Topographic images reveal that each metallic Mg layer is formed by 2D islands coalescence process on top of the silicide interfacial layer. During oxidation of the Mg monolayer, the interfacial silicide layer acts as diffusion barrier for the oxygen atoms with a decomposition of the silicide film to a magnesium oxide as function of O2 exposure

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Atom redistribution during crystallization of a B and P co-doped amorphous Si layer produced by Si and P chemical vapor co-deposition and B implantation has been investigated. The crystallization of the entire layer is quasi-instantaneous for annealing temperature greater than 650 °C. The crystallization rate is well reproduced by the Avrami-Johnson-Mehl-Kolmogorov model of transformation. The Avrami n is found equal to 4, which is corresponding to 3D bulk crystallization. Crystallization promotes a non-Fickian redistribution of B atoms, allowing for an abrupt interface between B-doped and B-undoped regions. After crystallization, B diffuses in the polycrystalline Si layer for concentrations lower than 1.5  1020 at cm3 via the type B kinetic regime. Crystallization has no significant (or detectable) influence on the P profile. For temperatures higher than 750 °C, P diffuses in the poly-Si layer towards the region of highest B concentration via the type B kinetic regime, leading to P uphill diffusion. This phenomenon can be simulated considering chemical interactions between B and P atoms in both grains and grain boundaries.