Search results for "GaP"
showing 10 items of 1144 documents
Norvège et Singapour, des écoles modèles
2018
National audience; L'école de Norvège et celle de Singapour sont régulièrement citées en exemple. Elles ont en commun d'être parfaitement en phase avec les grandes priorités nationales : l'égalité et la démocratie pour l'une, la performance et la prospérité pour l'autre.
Modelling the labour market of minority ethnic groups
2012
Abstract This paper investigates the effects, in terms of labour and macroeconomic indicators, of closing the gap between the ethnic minority employment rate and the overall population rate using a computable general equilibrium modelling framework. The labour market has been integrated by indicators related to ethnicity, employment status and occupational class. The policy test has been designed for the UK. According to the results, the policy actions aimed to remove the barriers that contribute to the unemployment of the minority ethnic groups improve not only the employment and occupational status of these groups, but the effects are also positive in terms of aggregate employment, GDP, t…
Should I use touchscreen tablets rather than computers and mice in TDS trials?
2016
International audience; Internet technologies are increasingly used as tools in sensory analysis. Thus, it would be a natural step forward for sensory science to move beyond the laboratory, into people's homes. Therefore, working with consumer IT devices like touchscreen tablets in sensory science should be taken into consideration. Working with the intuitive concept of dominance, Temporal Dominance of Sensations (TDS) requires a non-analytical answer from the subject. Using a touchscreen tablet instead of a classic mouse could reduce the cognitive load and favor a more instinctive answer. Indeed, it was proven that touch interaction is natural and efficient, and that finger pointing is fas…
Quantum Monte Carlo study of high pressure solid molecular hydrogen
2013
We use the diffusion quantum Monte Carlo (DMC) method to calculate the ground state phase diagram of solid molecular hydrogen and examine the stability of the most important insulating phases relative to metallic crystalline molecular hydrogen. We develop a new method to account for finite-size errors by combining the use of twist-averaged boundary conditions with corrections obtained using the Kwee-Zhang-Krakauer (KZK) functional in density functional theory. To study band-gap closure and find the metallization pressure, we perform accurate quasi-particle many-body calculations using the $GW$ method. In the static approximation, our DMC simulations indicate a transition from the insulating…
Optical and dielectric properties of MoO 3 nanosheets for van der Waals heterostructures
2021
Two-dimensional (2D) insulators are a key element in the design and fabrication of van der Waals heterostructures. They are vital as transparent dielectric spacers whose thickness can influence both the photonic, electronic, and optoelectronic properties of 2D devices. Simultaneously, they provide protection of the active layers in the heterostructure. For these critical roles, hexagonal Boron Nitride (hBN) is the dominant choice due to its large bandgap, atomic flatness, low defect density, and encapsulation properties. However, the broad catalogue of 2D insulators offers exciting opportunities to replace hBN in certain applications that require transparent thin layers with additional opti…
Systematical, experimental investigations on LiMgZ (Z= P, As, Sb) wide band gap semiconductors
2011
This work reports on the experimental investigation of the wide band gap compounds LiMgZ (Z = P, As, Sb), which are promising candidates for opto-electronics and anode materials for Lithium batteries. The compounds crystallize in the cubic (C1_b) MgAgAs structure (space group F-43m). The polycrystalline samples were synthesized by solid state reaction methods. X-ray and neutron diffraction measurements show a homogeneous, single-phased samples. The electronic properties were studied using the direct current (DC) method. Additionally UV-VIS diffuse reflectance spectra were recorded in order to investigate the band gap nature. The measurements show that all compounds exhibit semiconducting be…
Prediction of Weak Topological Insulators in Layered Semiconductors
2012
We report the discovery of weak topological insulators by ab initio calculations in a honeycomb lattice. We propose a structure with an odd number of layers in the primitive unit-cell as a prerequisite for forming weak topological insulators. Here, the single-layered KHgSb is the most suitable candidate for its large bulk energy gap of 0.24 eV. Its side surface hosts metallic surface states, forming two anisotropic Dirac cones. Though the stacking of even-layered structures leads to trivial insulators, the structures can host a quantum spin Hall layer with a large bulk gap, if an additional single layer exists as a stacking fault in the crystal. The reported honeycomb compounds can serve as…
Patterning and tuning of electrical and optical properties of graphene by laser induced two-photon oxidation
2015
Graphene, being an ultrathin, durable, flexible, transparent material with superior conductivity and unusual optical properties, promises many novel applications in electronics, photonics and optoelectronics. For applications in electronics, patterning and modification of electrical properties is very desirable since pristine graphene has no band gap. Here we demonstrate a simple all-optical patterning method for graphene, based on laser induced two-photon oxidation. By tuning the intensity of irradiation and the number of pulses the level of oxidation can be controlled to high precision and, therefore, a band gap can be introduced and electrical and optical properties can be continuously t…
Nonmagnetic and magnetic thiolate-protected Au25superatoms on Cu(111), Ag(111), and Au(111) surfaces
2012
Geometry, electronic structure, and magnetic properties of methylthiolate-stabilized Au$_{25}$L$_{18}$ and MnAu$_{24}$L$_{18}$ (L = SCH$_3$) clusters adsorbed on noble-metal (111) surfaces have been investigated by using spin-polarized density functional theory computations. The interaction between the cluster and the surface is found to be mediated by charge transfer mainly from or into the ligand monolayer. The electronic properties of the 13-atom metal core remain in all cases rather undisturbed as compared to the isolated clusters in gas phase. The Au$_{25}$L$_{18}$ cluster retains a clear HOMO - LUMO energy gap in the range of 0.7 eV to 1.0 eV depending on the surface. The ligand layer…
Ab initiolattice dynamical studies of silicon clathrate frameworks and their negative thermal expansion
2014
The thermal and lattice dynamical properties of seven silicon clathrate framework structures are investigated with ab initio density functional methods (frameworks I, II, IV, V, VII, VIII, and H). The negative thermal expansion (NTE) phenomenon is investigated by means of quasiharmonic approximation and applying it to equal time displacement correlation functions. The thermal properties of the studied clathrate frameworks, excluding the VII framework, resemble those of the crystalline silicon diamond structure. The clathrate framework VII was found to have anomalous NTE temperature range up to 300 K and it is suitable for further studies of the mechanisms of NTE. Investigation of the displa…