Large Variety Of Electronic Properties Research Articles

Electronic band gap of van der Waals α-As2Te3 crystals

van der Waals materials offer a large variety of electronic properties depending on chemical composition, number of layers, and stacking order. Among them, As2Te3 has attracted attention due to the promise of outstanding electronic properties and high photo-response. Precise experimental determinations of the electronic properties of As2Te3 are yet sorely needed for better understanding of potential properties and device applications. Here, we study the structural and electronic properties of α-As2Te3. Scanning transmission electron microscopy coupled to energy x-ray dispersion and micro-Raman spectroscopy all confirm that our specimens correspond to α-As2Te3. Scanning tunneling spectroscopy (STS) at 4.2 K demonstrates that α-As2Te3 exhibits an electronic bandgap of about 0.4 eV. The valence-band maxima are located at −0.03 eV below the Fermi level, thus confirming the residual p-type character of our samples. The material can be exfoliated, revealing the (100) anisotropic surface. Transport measurements on a thick exfoliated sample (bulk-like) confirm the STS results. These findings allow for a deeper understanding of the As2Te3 electronic properties, underlying the potential of V-VI semiconductors for electronic and photonic technologies.

Functionalisation of hexagonal boron phosphide (h-BP) monolayer via atomic adsorption

ABSTRACTIn this study, we investigate the adsorption properties of Fe, Co, Ni, Cu, Zn, In, Tl, Ar atoms on hexagonal boron phosphide monolayer (h-BP) using density functional theory within both GGA and LDA functionals. Bare h-BP is a direct gap semiconductor with planar structure. The adsorption of the atoms on h-BP exhibits a large variety of electronic properties like semiconducting, metallic, and half-metallic states. Fe- and Ni-adsorbed h-BPs show semiconducting character with decreased band gaps. Ni atom is strongly adsorbed on the surface giving largest adsorption energy observed in this work. Fe-adsorbed system is a semiconducting ferromagnet with 1.95 magnetic moment. Co adsorption results in a half-metallic behaviour with 1.00 net magnetic moment and a perfect spin polarisation at Fermi level. Cu, In, and Tl adsorbed h-BP systems show metallic character. The results obtained show that h-BP surface can be functionalised via adsorption of related single atoms and can be suitable for various applications in optoelectronics and spintronics.

Novel two-dimensional silicon-carbon binaries by crystal structure prediction.

The semimetallic bandstructure of graphene and silicene limit their use in functional devices. Mixing silicon and carbon offers a rather unexplored pathway to build semiconducting sheets compatible with current Si-based electronics. We present here a complete theoretical study of the phase diagram of two-dimensional silicon-carbon binaries. To scan the composition range, we employ an ab initio global structural prediction method, complemented by exhaustive enumeration of two-dimensional structure prototypes. We find a wealth of two-dimensional low-energy structures, from standard honeycomb single- and double-layers, passing by dumbbell geometries, to carbon nanosheets bridged by Si atoms. Many of these phases depart from planarity, either through buckling, or by germinating three-dimensional networks with a mixture of sp2 and sp3 bonds. We further characterize the most interesting crystal structures, unveiling a large variety of electronic properties, that could be exploited to develop high-performance electronic devices at the nanoscale.

Evidence of direct electronic band gap in two-dimensional van der Waals indium selenide crystals

Metal monochalcogenide compounds offer a large variety of electronic properties depending on chemical composition, number of layers, and stacking order. Among them, the InSe has attracted much attention due to the promise of outstanding electronic properties, attractive quantum physics, and high photoresponse. Precise experimental determination of the electronic structure of InSe is sorely needed for better understanding of potential properties and device applications. Here, combining scanning tunneling spectroscopy (STS) and two-photon photoemission spectroscopy, we demonstrate that InSe exhibits a direct band gap of about 1.25 eV located at the \ensuremath{\Gamma} point of the Brillouin zone. STS measurements underline the presence of a finite and almost constant density of states (DOS) near the conduction-band minimum. This particular DOS is generated by a poorly dispersive nature of the top valence band, as shown by angle-resolved photoemission spectroscopy (ARPES) investigation. In fact, a hole effective mass of about ${m}^{*}/{m}_{0}=\ensuremath{-}0.95$ ($\overline{\mathrm{\ensuremath{\Gamma}}K}$ direction) was measured. Moreover, using ARPES measurements a spin-orbit splitting of the deeper-lying bands of about 0.35 eV was evidenced. These findings allow a deeper understanding of the InSe electronic properties underlying the potential of III-VI semiconductors for electronic and photonic technologies.

Structural and electronic properties of rare earth skutterudites EuRu4P12: a first principle study

Ternary skutterudites materials exhibit a large variety of electronic properties due to the unpaired 3d and 4f electronic configuration of the transition and rare-earth elements respectively. In this communication we have performed structural optimization and electronic structure calculation of the Rare Earth Skutterudite EuRu4P12, using FP-LAPW method. The optimized lattice parameter is in good agreement with the available experimental value. No band gap between the valence band and the conduction band has been observed which indicates that its character is metallic.

Complete analysis of a transmission electron diffraction pattern of a MoS2–graphite heterostructure

The combination of various 2D layered materials in multilayer heterostructures arises great interest in the current science. Due to the large variety of electronic properties of the group of 2D layered materials the combination opens a new pathway towards ultrasmall electronic devices. In this contribution we present a full mathematical description of multilayer heterostructure samples and their diffraction patterns including a proposal of a consistent assignment of the superstructure diffraction spots. A 27nm thick MoS2–graphite heterostructure was produced and fully analysed with the methods presented in this paper.

Broad HOMO–LUMO gap tuning through the coordination of a single phosphine, aminophosphine or phosphite onto a Ru(tpy)(bpy)2+ core

The synthesis of new ruthenium(II) terpyridine bipyridine complexes bearing a phosphorus(III) ligand is presented. The steric and electronic properties of the phosphorus ligand were varied using aminophosphines, alkyl and aryl phosphites and the bulky tri(isopropyl)phosphine. All complexes were characterized by multi-nuclear NMR spectroscopy, mass spectrometry and X-ray diffraction analysis. The electronic properties of the complexes were probed by cyclic voltammetry, absorption and luminescence spectroscopy. The complexes do not show luminescence at room temperature, whereas at 77 K in an alcoholic matrix, emission is observed in the range 600-650 nm with lifetimes of 3.5-5.5 micros, originating from 3MLCT states. The MLCT transition spans over 65 nm, which corresponds to a variation of 0.4 eV in the HOMO-LUMO gap. The oxidation potential of the ruthenium varies over a broad range of 290 mV, from +1.32 V vs. SCE with L = PiPr3 to +1.61 V vs. SCE with L = P(OPh)3. This range is unprecedented upon the variation of a single monodentate ligand coordinated by the same heteroatom in the same oxidation and charge states. This work underlines the specific capacity of phosphorus in bringing up a large variety of electronic properties by changing its substituents.

Stability and electronic structure ofBxNyCz nanotubes

We apply a first-principles method, based on the density functionaltheory, to calculate the structural stability and electronic properties ofBxNyCz nanotubes. We follow the evolution of the electronic and structural properties as a functionof the composition, atomic structure and nanotube diameter. The results indicate thatnanotubes present a large variety of electronic properties, showing a remarkabledependence on these parameters. The formation energy decreases with the tube diameter,D, and has a strong dependence on the tube stoichiometry. Additionally, the results show that thestrain energy of the tubes, relative to the corresponding unstrained sheet material, varies as1/Dn. ForBC2N the classicalstrain law (n = 2) is clearly obtained. Nevertheless, in the case of BCN, the exact value ofn is a matter of discussion.