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The growth of bilayers of two-dimensional (2D) materials on conventional 3D semiconductors results in 2D/3D hybrid heterostructures, which can provide additional advantages over more established 3D semiconductors while retaining some specificities of 2D materials. Understanding and exploiting these phenomena hinge on knowing the electronic properties and the hybridization of these structures. Here, we demonstrate that a rhombohedral-stacked bilayer (AB stacking) can be obtained by molecular beam epitaxy growth of tungsten diselenide (WSe2) on a gallium phosphide (GaP) substrate. We confirm the presence of 3R-stacking of the WSe2bilayer structure using scanning transmission electron microscopy (STEM) and micro-Raman spectroscopy. Also, we report high-resolution angle-resolved photoemission spectroscopy (ARPES) on our rhombohedral-stacked WSe2bilayer grown on a GaP(111)B substrate. Our ARPES measurements confirm the expected valence band structure of WSe2with the band maximum located at the Γ point of the Brillouin zone. The epitaxial growth of WSe2/GaP(111)B helps to understand the fundamental properties of these 2D/3D heterostructures, toward their implementation in future devices.

Epitaxial growth of WTe2offers significant advantages, including the production of high-quality films, possible long-range in-plane ordering, and precise control over layer thicknesses. However, the mean island size of WTe2grown by molecular beam epitaxy (MBE) in the literature is only a few tens of nanometers, which is not suitable for the implementation of devices at large lateral scales. Here we report the growth of Td-WTe2ultrathin films by MBE on monolayer (ML) graphene, reaching a mean flake size of ≃110 nm, which is, on overage, more than three times larger than previous results. WTe2films thicker than 5 nm have been successfully synthesized and exhibit the expected Td phase atomic structure. We rationalize the epitaxial growth of Td-WTe2and propose a simple model to estimate the mean flake size as a function of growth parameters that can be applied to other transition metal dichalcogenides (TMDCs). Based on nucleation theory and the Kolmogorov–Johnson–Meh–Avrami (KJMA) equation, our analytical model supports experimental data showing a critical coverage of 0.13 ML above which WTe2nucleation becomes negligible. The quality of monolayer WTe2films is demonstrated by electronic band structure analysis using angle-resolved photoemission spectroscopy (ARPES), which is in agreement with first-principles calculations performed on free-standing WTe2and previous reports. We found electron pockets at the Fermi level, indicating a n-type doping of WTe2with an electron density of n= 2.0 ± 0.5 × 1012cm–2for each electron pocket.

A new method was developed for the high precision measurement of Rb, Sr, Ba, and Pb concentrations in silicate rocks. This method is based on the combined use of isotope dilution and ICP quadrupole mass spectrometry, with matrix element removal. The concomitant separation of the analytes is achieved by extraction chromatography (Ba, Sr, Pb) and inorganic cation exchange chromatography (Rb), on two small tandem columns filled with 0.1 ml of “Sr resin” and 1 ml of zirconium (or titanium) phosphate, respectively. Compared to previous separation schemes based on cation- and anion-exchange, this method allows the rapid, concomitant isolation of four trace elements of great interest in geochemistry, with a greatly reduced volume of reagents. The capabilities of the method in terms of precision (equal to or better than 1% RSD) and accuracy are demonstrated by duplicate analyses of four international reference materials (BIR-1, BHVO-1, AGV-1 and RGM-1, from the US Geological Survey) representative of various silicate rock bulk compositions and spanning a large range (0.2–1000 µg g−1) of analyte concentrations.

Human multipotential hematopoietic progenitor cells can be assayed by their ability to form colonies of mixed cell lineages in vitro. These cells display la-like antigens and HLA-A,B,C antigens as evidenced by inhibition of colony formation by specific monoclonal antibodies and complement.

The radiogalaxy 3C324 has recently raised considerable interest as one of the most distant (redshift z = 1.206) and luminous known galaxies. Here we report new observations of this object at Canada–France–Hawaii Telescope which confirm our previous predictions of the presence of an intervening gravitational lens. First, a multiple structure is revealed by our charge-coupled device (CCD) broadband imagery. Second, following our previous identification in the 3C324 spectrum of an additional line system at z=0.84, subsequent CCD observation through interferential filters were planned. In a wavelength range corresponding to an emission line at z=0.84 only the central component is detected, while only outer components are seen in a range corresponding to a line redshifted by z=1.206. These observations are interpreted as the first example of gravitational multiple imaging of a giant radiogalaxy by a foregound object. So galaxy 3C324 seems to be a gravitational mirage—though further spectroscopic observations will be needed to establish whether the two images have similar spectra.

The Subaru Prime Focus Spectrograph (PFS) is a massively multiplexed fiber-fed optical and near-infrared three-arm spectrograph (Nfiber= 2400, 380 ≤ λ ≤ 1260 nm, 1 $_{.}^{\circ}$3 diameter field of view). Here, we summarize the science cases in terms of provisional plans for a 300-night Subaru survey. We describe plans to constrain the nature of dark energy via a survey of emission line galaxies spanning a comoving volume of 9.3 h−3Gpc3in the redshift range 0.8 < z< 2.4. In each of six redshift bins, the cosmological distances will be measured to 3% precision via the baryonic acoustic oscillation scale, and redshift-space distortion measures will constrain structure growth to 6% precision. In the near-field cosmology program, radial velocities and chemical abundances of stars in the Milky Way and M 31 will be used to infer the past assembly histories of spiral galaxies and the structure of their dark matter halos. Data will be secured for 106stars in the Galactic thick-disk, halo, and tidal streams as faint as V∼ 22, including stars with V< 20 to complement the goals of the Gaia mission. A medium-resolution mode with R= 5000 to be implemented in the red arm will allow the measurement of multiple α-element abundances and more precise velocities for Galactic stars. For the galaxy evolution program, our simulations suggest the wide wavelength range of PFS will be powerful in probing the galaxy population and its clustering over a wide redshift range. We plan to conduct a color-selected survey of 1 < z< 2 galaxies and AGN over 16 deg2to J≃ 23.4, yielding a fair sample of galaxies with stellar masses above ∼1010M⊙at z≃ 2. A two-tiered survey of higher redshift Lyman break galaxies and Lyman alpha emitters will quantify the properties of early systems close to the reionization epoch.