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Molecular beam epitaxy technique has been used to deposit a single layer and a bilayer of MoSe 2 on sapphire. Extensive characterizations including in-situ and ex-situ measurements show that the layered MoSe 2 grows in a scalable manner on the substrate and reveals characteristics of a stoichiometric 2H-phase. The layered MoSe 2 exhibits polycrystalline features with domains separated by defects and boundaries. Temperature and magnetic field dependent resistivity measurements unveil a carrier hopping character described within two-dimensional variable range hopping mechanism. Moreover, a negative magnetoresistance was observed, stressing a fascinating feature of the charge transport under the application of a magnetic field in the layered MoSe 2 system. This negative magnetoresistance observed at millimeter-scale is similar to that observed recently at room temperature inWS2 flakes at a micrometer scale [Zhang et al., Appl. Phys. Lett. 108, 153114 (2016)]. This scalability highlights the fact that the underlying physical mechanism is intrinsic to these two-dimensional materials and occurs at very short scale., 15 pages, 6 figures

We report the growth of InAs/InAs1-xSbx single and double heterostructured nanowires by Au-assisted chemical beam epitaxy. The InAs1-xSbx nanowire segments have been characterized in a wide range of antimony compositions. Significant lateral growth is observed at intermediate compositions (x similar to 0.5), and the nucleation and step-flow mechanism leading to this lateral growth has been identified and described. Additionally, CuPt ordering of the alloy has been observed with high resolution transmission electron microscopy, and it is correlated to the lateral growth process. We also show that it is possible to regrow InAs above the InAsSb alloy segment, at least up to an intermediate antimony composition. Such double heterostructures might find applications both as mid-infrared detectors and as building blocks of electronic devices taking advantage of the outstanding electronic and thermal properties of antimonide compound semiconductors.

GaAs was used as the target material for the deposition of GaN films by reactive sputtering. The films were grown at different compositions of the sputtering gas mixture (0-100% nitrogen in argon) at substrate temperatures of 450 and 550 degrees C. The films were studied using XRD and XPS techniques. Even a small quantity of nitrogen in the sputtering medium was found to prevent the formation of GaAs on the substrate. Films grown at 550 degrees C using 100% nitrogen as the sputtering-reactive gas were found to be single phase (0002) oriented hexagonal gallium nitride and revealed complete absence of arsenic. (C) 1998 Elsevier Science S.A. .

Zinc phosphide (Zn3P2) is an ideal absorber candidate for solar cells thanks to its direct bandgap, earth-abundance, and optoelectronic characteristics, albeit it has been insufficiently investigated due to limitations in the fabrication of high-quality material. It is possible to overcome these factors by obtaining the material as nanostructures, e.g. via the selective area epitaxy approach, enabling additional strain relaxation mechanisms and minimizing the interface area. We demonstrate that Zn3P2 nanowires grow mostly defect-free when growth is oriented along the [100] and [110] of the crystal, which is obtained in nanoscale openings along the [110] and [010] on InP(100). We detect the presence of two stable rotated crystal domains that coexist in the structure. They are due to a change in the growth facet, which originates either from the island formation and merging in the initial stages of growth or lateral overgrowth. These domains have been visualized through 3D atomic models and confirmed with image simulations of the atomic scale electron micrographs. Density functional theory simulations describe the rotated domains' formation mechanism and demonstrate their lattice-matched epitaxial relation. In addition, the energies of the shallow states predicted closely agree with transition energies observed by experimental studies and offer a potential origin for these defect transitions. Our study represents an important step forward in the understanding of Zn3P2 and thus for the realisation of solar cells to respond to the present call for sustainable photovoltaic technology., We acknowledge Martin Friedl, Didem Dede, Nicholas Morgan, and Wonjong Kim for helpful discussions regarding selective area growth and the substrate patterning procedures. M. C. S., S. M. S., P. T. V. and J. A. acknowledge funding from Generalitat de Catalunya 2017 SGR 327. ICN2 is supported by the Severo Ochoa programme from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. M. C. Spadaro has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 754510 (PROBIST) and the Severo Ochoa programme. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 823717 – ESTEEM3. Authors acknowledge the use of instrumentation provided by the National Facility ELECMI ICTS, node “Laboratorio de Microscopías Avanzadas” at University of Zaragoza. S. E. S., E. Z. S., M. Z., R. P., J. B. L. and A. F. i M. were supported by SNSF Consolidator grant BSCGI0-157705 and the Max-Planck-EPFL-Center for Molecular Nanoscience and Technology. N. Y. D. acknowledges the UK Engineering and Physical Sciences Research Council (EPSRC) for funding (Grant No. EP/S001395/1). The DFT calculations were performed using the computational facilities of the Advanced Research Computing @ Cardiff(ARCCA) Division, Cardiff University.