Electronic Properties Of Hydrogen Research Articles

Structural and electronic properties of hydrogen - functionalized armchair germanene nanoribbons: A first-principles study

Structural and electronic properties of armchair germanene nanoribbons functionalized by hydrogen atoms (H-AGeNR) are studied through density functional theory (DFT) method. The DFT quantities for analyzing the structural and electronic properties are fully developed through the DFT calculations, including the functionalization energy, relaxed geometric parameters, orbital- and atom-decomposed energy bands, electronic density of states, charge density, and charge density difference. Under hydrogen functionalization, the functionalization energy is achieved at -2.59 eV, and the structural parameters are slightly distorted. This provides evidence of good structural stability of the functionalized system. Besides, the very strong bonds of H-Ge are created because the electrons are transfered from Ge atoms to H adatoms, which induces hole density in the functionalized system, which is regarded as p-type doping. As a result, the π bonds of 4pz orbitals at low-lying energy are fully terminated by the strong H-Ge covalent bonds, in which the strong hybridizations of H-1s and Ge-(4s, 4px, 4py, and 4pz) orbitals have occurred at deep valence band. The termination of π bonds leads to the opened energy gap of 2.01 eV in the H-functionalized system that belongs to the p-type semiconductor. The enriched properties of the H-functionalized system identify that the H-functionalized system...

Tuning flexoelectricty and electronic properties of zig-zag graphene nanoribbons by functionalization

The flexoelectric and electronic properties of zig-zag graphene nanoribbons are explored under mechanical bending using state of the art first principles calculations. A linear dependence of the bending induced out of plane polarization on the applied strain gradient is found. The inferior flexoelectric properties of graphene nanoribbons can be improved by more than two orders of magnitude by hydrogen and fluorine functionalization (CH and CF nanoribbons). A large out of plane flexoelectric effect is predicted for CF nanoribbons. The origin of this enhancement lies in the electro-negativity difference between carbon and fluorine atoms, which breaks the out of plane charge symmetry even for a small strain gradient. The flexoelectric effect can be further improved by co-functionalization with hydrogen and fluorine (CHF Janus-type nanoribbon), where a spontaneous out of plane dipole moment is formed even for flat nanoribbons. We also find that bending can control the charge localization of valence band maxima and therefore enables the tuning of the hole effective masses and band gaps. These results present an important advance towards the understanding of flexoelectric and electronic properties of hydrogen and fluorine functionalized graphene nanoribbons, which can have important implications for flexible electronic applications.

Properties of hydrogen doped Cu nanowires and nanocontacts: a density-functional theory study

Using first-principles calculations based on density-functional theory, we systematically investigate the structural and electronic properties of hydrogen (hydrogen atoms and H2 molecule) doped Cu chain nanowires and nanocontacts. Various possible configurations of Cu chain nanowires and nanocontacts doped with hydrogen impurities are considered. These Cu chain nanowires and nanocontacts are stabilized by hydrogen impurities beyond their classical breaking point. The formed metal-impurity bond is much stronger than the metal–metal bond. Upon elongation, the doped Cu chain nanowire tends to break from the remote metal–metal bond and the doped Cu nanocontact will break from metal–metal chain bond. The interaction between hydrogen impurities and Cu atoms alters the interatomic bonding and hybridization of electronic states in Cu chain nanowires and nanocontacts. Additionally, the dissociation of H2 molecule is observed when H2 molecule doped in Cu nanocontact, which can be used in catalytic application.

Role of covalent and metallic intercalation on the electronic properties of epitaxial graphene on SiC(0001)

We present an orbital-resolved density functional theory study on the electronic properties of hydrogen and lithium intercalated graphene grown on the Si face of SiC. Starting from the $(6\sqrt3\times6\sqrt3)R30^{\circ}$ surface reconstruction of the graphene/SiC heterosystem, we find that both H and Li can restore the ideal structural characteristics of the two nonequivalent junction parts (i.e. graphene and the SiC substrate) when inserted at the interface. However, the chemical/electrostatic interactions remain different for the two cases. Hence, H-intercalated epitaxial graphene is subject to a sublattice symmetry-breaking electronic interference that perturbs the Dirac point, whereas Li intercalation gives rise to a highly $n$-doped system due to a nonuniform delocalization of Li charges. Results bring to discussion the role of substrate engineering in epitaxial graphene on SiC.

Theoretical Investigation on the Structure and Electronic Properties of Hydrogen- and Alkali-Metal-Doped Gold Clusters and Their Interaction with CO: Enhanced Reactivity of Hydrogen-Doped Gold Clusters

The electronic structure and properties of pristine gold clusters Aun as well as the alkali-metal- and hydrogen-atom-doped clusters Aun−1X, where n = 2−8 and X = Li, Na, and H, have been investigat...

Electronic properties of hydrogen- and oxygen-terminated diamond surfaces exposed to the air

The electronic properties of hydrogen- and oxygen-terminated diamond surfaces exposed to the air are investigated by scanning probe microscopy (SPM). The results indicate that for the hydrogen-terminated diamond surface a shallow acceptor above the valence-band-maximum (VBM) appears in the band gap. However, the oxygen-terminated diamond film exhibits a high resistivity with a wide band gap. Based on the density-functional-theory, the densities of states, corresponding to molecular adsorbate in hydrogenated and oxygenated diamond (100) surfaces, are studied. The results show that the shallow acceptor in the band gap for the hydrogen-terminated diamond film can be attributed to the interaction between the surface C–H bonding orbitals and the adsorbate molecules, while for the oxygen-terminated diamond film, the interaction between the surface C–O bonding orbitals and the adsorbate molecules can induce occupied states in the valence-band.

Hydrogen adsorption onRuO2(110): Density-functional calculations

The structural, vibrational, energetic, and electronic properties of hydrogen at the stoichiometric $\mathrm{Ru}{\mathrm{O}}_{2}(110)$ termination are studied using density-functional theory. The oxide surface is found to bind both molecular and dissociated ${\mathrm{H}}_{2}$. Apart from the most stable configuration in the form of hydroxyl groups (monohydrides) at the undercoordinated ${\mathrm{O}}^{\mathrm{br}}$ surface anions, we also identify a molecular state at the undercoordinated ${\mathrm{Ru}}^{\mathrm{cus}}$ atoms (dihydrogen) and a waterlike species (dihydride) at the ${\mathrm{O}}^{\mathrm{br}}$ sites. Hydrogen adsorption at ${\mathrm{O}}^{\mathrm{br}}$ sites increases the reactivity of the neighboring ${\mathrm{Ru}}^{\mathrm{cus}}$ sites, which are believed to play a key role in catalytic oxidation reactions.

Electronic properties of hydrogen and oxygen terminated surfaces of polycrystalline diamond films

The electronic properties of hydrogen and oxygen terminated surfaces of polycrystalline diamond films are investigated in the dark and under illumination by temperature dependent surface conductivity, field dependence of photocurrent and spectrally resolved photoelectron yield measurements. The as grown characteristics, as well as the observed changes induced by thermal annealing and sulphochromic treatment are interpreted in terms of surface band bending controlled by H-termination and by the presence of adsorbates, whose extention can be further modulated by illumination and by the laterally applied bias.

Electronic Properties of Hydrogen Exposed III–V Semiconductor Surfaces

Electronic Properties of Hydrogen Exposed III–V Semiconductor Surfaces

Charge-transfer states in dense hydrogenCharge-transfer states in dense hydrogen

THE electronic properties of hydrogen, from the gas phase to the solid state, are fundamental to our understanding of the chemical bond1. The strong covalent bond of diatomic hydrogen persists in low-density condensed phases, where the molecules interact very weakly through van der Waals forces2. At very high densities, molecular bonding has long been predicted to give way to a mon-atomic and presumably metallic lattice3. At intermediate densities, intermolecular interactions are expected to increase; however, the relative strengths of the intermolecular and intramolecular interactions, and their effect on physical and chemical properties, have received comparatively little attention theoretically. Recent diamond-anvil-cell studies have revealed a range of unexpected phenomena in solid hydrogen at these densities4. Here we show that marked changes in the infrared and Raman spectra of the intramolecular stretching modes (vibrons)5 with increasing pressure can be interpreted in a manner analogous to the behaviour of organic charge-transfer salts at ambient pressure, including those exhibiting pressure-induced neutral-to-ionic transitions6,7. Increased molecular overlap in dense hydrogen leads to symmetry breaking, which makes possible charge-transfer states between adjacent H2 molecules. The consequent changes in bond strength and in vibron frequencies are evident in the spectra. These findings present a new picture of dense hydrogen and highlight the advantages of a localized, 'chemical' description of the bonding.

Electronic properties of the hydrogen-carbon complex in crystalline silicon

The electronic properties of hydrogen in carbon-doped n-type silicon have been studied using deep-level transient spectroscopy. It is demonstrated that hydrogen (H) in the presence of substitutional carbon (C) forms an H-C complex with an energy level located ≊0.16 eV below the edge of the conduction band. The H-C complex is a deep donor which is only stable in the positively charged state and dissociates after capture of free electrons for temperatures T≥300 K. The H-C dissociation kinetics yield an activation energy of 0.73 eV.

A hydrogen-carbon related deep donor in crystalline n-Si:C

The electronic properties of hydrogen in phosphorus-doped monocrystalline silicon containing different amounts of carbon have been investigated by deep level transient spectroscopy. The experiments reveal that after a reverse bias annealing (RBA) treatment hydrogen, in the presence of carbon, forms a deep and charge-state-dependent carbon-hydrogen level located approximately 0.16 eV below the conduction band edge. This trap center is stable only in the positively charged state and vanishes after capture of electrons for temperatures greater than or equal to 300 K.

Charge-state-dependent hydrogen-carbon-related deep donor in crystalline silicon.

The electronic properties of hydrogen in carbon-doped n-type silicon have been studied using deep-level transient spectroscopy. The results show for the first time that hydrogen in the presence of carbon forms a deep and charge-state-dependent center located \ensuremath{\sim}0.16 eV below the edge of the conduction band. This trap center is a deep donor which is only stable in the positively charged state and anneals after capture of electrons for temperatures T\ensuremath{\ge}300 K.

Size effects in the electronic properties of hydrogen and helium embedded in small metal clusters: The self-consistent spherical-jellium-particle model

The electronic properties of H and He, as the simplest examples for reactive and inert atomic systems embedded in small metal clusters, are investigated within the self-consistent spherical-jellium-particle model. Physical properties of interest are the modification of the electronic properties of the jellium particle (as a model for real clusters of the sp-bonded metals) by light impurities and vice versa, the modification of the free-atom properties when the atom is embedded in a metallic host which exhibits size-dependent quantum-mechanical properties. Quantities investigated include size-dependent impurity ionization potentials, relaxation shifts and static screening properties, size-dependent impurity immersion energies, and size-dependent impurity-induced quenching of the collective modes in small metal particles. Among other predictions it is demonstrated how the so-called magic numbers are modified by impurity embedding. The experimental verification of these predictions could give additional evidence for the electronic shell model for these particles.

Structural and electronic properties of hydrogen in the potassium-hydrogen-graphite ternary intercalation compound C8KH

A proton NMR study was carried out on a second-stage potassium-hydrogen-graphite intercalation compound, ${\mathrm{C}}_{8}$${\mathrm{KH}}_{\mathrm{x}}$ (x=0.55), in a powder form within the temperature range 1.5--77 K. An inhomogeneously broadened NMR signal (around 40 kHz in full width at half maximum) was observed, but the intrinsic linewidth of the spin isochromat, about 3.6 kHz, was determined from the spin-echo envelope. The shape of the echo envelope was explained by assuming a regular two-dimensional structure of dissociated hydride ions. The inhomogeneous broadening may possibly be ascribed to localized electron spins of the order of 100 ppm. The spin-lattice relaxation mechanisms were divided into two contributions, the metallic process and the process due to localized electron spins. Analysis of the metallic relaxation component revealed the existence of a small local density of states at the Fermi level at hydrogen sites, N(${E}_{F}$${)}_{\mathrm{H}}$=0.014 states per eV per spin per hydrogen atom. The hydrogen atomic plane was revealed to be weakly metallic. A possible electronic structure is discussed.