Ab initio study of Ru-terminated and Ru-doped armchair graphene nanoribbons

Cataloged from PDF version of article.We investigate the effects of ruthenium (Ru) termination and Ru doping on the electronic properties of armchair graphene nanoribbons (AGNRs) using first-principles methods. The electronic band structures, geometries, density of states, binding energies, band gap information, and formation energies of related structures are calculated. It is well founded that the electronic properties of the investigated AGNRs are highly influenced by Ru termination and Ru doping. With Ru termination, metallic band structures with quasi-zero-dimensional, onedimensional and quasi-one-dimensional density of states (DOS) behavior are obtained in addition to dominant one-dimensional behavior. In contrast to Ru termination, Ru doping introduces small but measurable (12.4 to 89.6 meV) direct or indirect band gaps. These results may present an additional way to produce tunable band gaps in AGNRs

First-principles calculations of Pd-terminated symmetrical armchair graphene nanoribbons

Cataloged from PDF version of article.The effects of Palladium (Pd) termination on the electronic properties of armchair graphene nanoribbons (AGNRs) were calculated by using ab initio calculations. After a geometric optimization process, the electronic band structures, density of states, and binding energies of AGNRs with N-a = 5-15 were calculated. Pd-termination was found to significantly influence the electronic properties of AGNRs. In DOS, many Q0D and Q1D type states were observed. Binding energy (BE) for single-side or both-side Pd-terminated structures represents characteristic drops with the increasing GNR width. With the increasing GNR width, the BEs of these structures become similar to hydrogenated structures. Because of the GNR width, dependent BE also gave information on the possible stiffness information, in which all of this information can be used in studies where controlled binding to graphene is required. (C) 2012 Elsevier B.V. All rights reserved

Electronic properties of Li-doped zigzag graphene nanoribbons

Zigzag graphene nanoribbons (ZGNRs) are known to exhibit metallic behavior. Depending on structural properties such as edge status, doping and width of nanoribbons, the electronic properties of these structures may vary. In this study, changes in electronic properties of crystal by doping Lithium (Li) atom to ZGNR structure are analyzed. In spin polarized calculations are made using Density Functional Theory (DFT) with generalized gradient approximation (GGA) as exchange correlation. As a result of calculations, it has been determined that Li atom affects electronic properties of ZGNR structure significantly. It is observed that ZGNR structure exhibiting metallic behavior in pure state shows half-metal and semiconductor behavior with Li atom. © 2016 Elsevier B.V

Effect of substitutional As impurity on electrical and optical properties of β-Si3N4 structure

β-Si3N4 is used as the gate dielectric for surface passivation in GaN-based, high-electron mobility transistors(HEMTs). In this study, the electrical and optical characteristics of the hexagonal β-Si3N4 crystal structure were calculated using density functional theory (DFT) and local-density approximation (LDA). Calculations of the electronic band structure and the density of states (DOS) were made for the pure β-Si3N4 crystal structure and the β-Si3N4 crystal doped with an arsenic (As) impurity atom. In addition, the optical properties such as the static dielectric constant, refractive index, extinction coefficient, absorption coefficient and reflection coefficient were examined depending on the photon energy. As a result of these calculations, it was observed that the As impurity atom drastically changed the electrical and optical properties of the pure β-Si3N4 crystalline structure, and improvements are suggested for potential further studies. © 2016 Elsevier Ltd. All rights reserved

Grain boundary related electrical transport in Al-rich AlxGa1 - xN layers grown by metal-organic chemical vapor deposition

Electrical transport data for Al-rich AlGaN layers grown by metal-organic chemical vapor deposition (MOCVD) are presented and analyzed in the temperature range 135-300 K. The temperature dependence of electrical conductivity indicated that conductivity in the films was controlled by potential barriers caused by carrier depletion at grain boundaries in the material. The Seto's grain boundary model provided a complete framework for understanding of the conductivity behavior. Various electrical parameters of the present samples such as grain boundary potential, donor concentration, surface trap density, and Debye screening length were extracted. © 2011 Pleiades Publishing, Ltd

The effect of InxGa1-xN back-barriers on the dislocation densities in Al0.31Ga0.69N/AlN/GaN/InxGa1-xN/GaN heterostructures (0.05 <= x <= 0.14)

Cataloged from PDF version of article.Al0.31Ga0.69N/AlN/GaN/InxGa1-xN/GaN heterostructures grown with the metal-organic chemical vapor deposition (MOCVD) technique with different InxGa1-xN back-barriers with In mole fractions of 0.05 <= x <= 0.14 were investigated by using XRD measurements. Screw, edge, and total dislocations, In mole fraction of back-barriers, Al mole fraction, and the thicknesses of front-barriers and lattice parameters were calculated. Mixed state dislocations with both edge and screw type dislocations were observed. The effects of the In mole fraction difference in the back-barrier and the effect of the thickness of front-barrier on crystal quality are discussed. With the increasing In mole fraction, an increasing dislocation trend is observed that may be due to the growth temperature difference between ultrathin InxGa1-xN back-barrier and the surrounding layers. (C) 2012 Elsevier B.V. All rights reserved

Electronic Properties of a Novel Boron Polymorph: Ogee-Borophene

In this computational study, a novel borophene polymorph, Ogee-Borophene, characterized by irregular decagon-shaped hollows was reported. The structure involves a deviation from hexagonal configurations found in all other known borophene polymorphs. The decagon-shaped hollow is highly related to the anisotropy of the structure, which results in three types of boron atoms with different electronic properties in the structure. In the study, the electronic structure and density of states of this novel structure were investigated with the help of density functional theory calculations. The electronic structure of Ogee-Borophene shows Dirac cone formations near the Fermi level. The discovery of a novel borophene polymorph, Ogee-Borophene, with irregular-shaped hollows represents a different point of view in the 2D materials field. The unique electronic properties of this material suggest that Ogee-Borophene has the potential to be used in a variety of applications, including transistors, and selective sensor applications without the need for additional doping

Structural parameters and electronic properties of 2D carbon allotrope: Graphene with a kagome lattice structure

In this paper, the electronic properties of a carbon allotrope, graphene with a kagome lattice structure, are investigated. Spin-polarized density functional theory (DFT) calculations with Grimme dispersion corrections were done. Bond lengths, electronic band structure, and projected density of states were calculated. Electronic band structure calculations show kagome flat-band formation with higher d-orbital contributed bonding behavior than the pristine graphene structure. The structural parameters and electronic band results of this 2D carbon allotrope show wider possible usage in many applications from desalination membranes to possible high temperature superconductors

Electronic properties of Li-doped zigzag graphene nanoribbons

Zigzag graphene nanoribbons (ZGNRs) are known to exhibit metallic behavior. Depending on structural properties such as edge status, doping and width of nanoribbons, the electronic properties of these structures may vary. In this study, changes in electronic properties of crystal by doping Lithium (Li) atom to ZGNR structure are analyzed. In spin polarized calculations are made using Density Functional Theory (DFT) with generalized gradient approximation (GGA) as exchange correlation. As a result of calculations, it has been determined that Li atom affects electronic properties of ZGNR structure significantly. It is observed that ZGNR structure exhibiting metallic behavior in pure state shows half-metal and semiconductor behavior with Li atom. (C) 2016 Elsevier B.V. All rights reserved