/Tag: Silicene

Computational insights and the observation of SiC nanograin assembly: towards 2D silicon carbide. (arXiv:1701.07387v2 [cond-mat.mtrl-sci] UPDATED)

2018-11-16T02:29:21+00:00November 16th, 2018|Categories: Publications|Tags: , , , , |

While an increasing number of two-dimensional (2D) materials, including graphene and silicene, have already been realized, others have only been predicted. An interesting example is the two-dimensional form of silicon carbide (2D-SiC). Here, we present an observation of atomically thin and hexagonally bonded nanosized grains of SiC assembling temporarily in graphene oxide pores during an atomic resolution scanning transmission electron microscopy experiment. Even though these small grains do not fully represent the bulk crystal, simulations indicate that their electronic structure already approaches that of 2D-SiC. This is predicted to be flat, but some doubts have remained regarding the preference of Si for sp$^{3}$ hybridization. Exploring a number of corrugated morphologies, we find completely flat 2D-SiC to have the lowest energy. We further compute its phonon dispersion, with a Raman-active transverse optical mode, and estimate the core level binding energies. Finally, we study the chemical reactivity of 2D-SiC, suggesting it is like silicene unstable against molecular absorption or interlayer linking. Nonetheless, it can form stable van der Waals-bonded bilayers with either graphene or hexagonal boron nitride, promising to further enrich the family of two-dimensional materials once bulk synthesis is achieved.

Published in: "arXiv Material Science".

Composition and Stacking Dependent Topology in Bilayers from the Graphene Family. (arXiv:1811.05525v1 [cond-mat.mtrl-sci])

2018-11-15T02:29:17+00:00November 15th, 2018|Categories: Publications|Tags: , , |

We present a compositional and structural investigation of silicene, germanene, and stanene bilayers from first-principles. Due to the staggering of the individual layers, several stacking patterns are possible, most of which are not available to the bilayer graphene. This structural variety, in conjunction with the presence of the spin-orbit coupling, unveil a diversity of the electronic properties, with the appearance of distinct band features, including orbital hybridization and band inversion. We show that for particular cases, the intrinsic spin Hall response exhibits signatures of non-trivial electronic band topology, making these structures promising candidates to probe Dirac-like physics.

Published in: "arXiv Material Science".

Compelling experimental evidence of a Dirac cone in the electronic structure of a 2D Silicon layer. (arXiv:1811.01291v1 [cond-mat.mtrl-sci])

2018-11-06T05:29:38+00:00November 6th, 2018|Categories: Publications|Tags: , , |

The remarkable properties of graphene stem from its two-dimensional (2D) structure, with a linear dispersion of the electronic states at the corners of the Brillouin zone (BZ) forming a Dirac cone. Since then, other 2D materials have been suggested based on boron, silicon, germanium, phosphorus, tin, and metal di-chalcogenides. Here, we present an experimental investigation of a single silicon layer on Au(111) using low energy electron diffraction (LEED), high resolution angle-resolved photoemission spectroscopy (HR-ARPES), and scanning tunneling microscopy (STM). The HR-ARPES data show compelling evidence that the silicon based 2D overlayer is responsible for the observed linear dispersed feature in the valence band, with a Fermi velocity of v_F ~10^(+6) m.s^(-1) comparable to that of graphene. The STM images show extended and homogeneous domains, offering a viable route to the fabrication of silicene-based opto-electronic devices.

Published in: "arXiv Material Science".

Silicene on IrSi3 crystallites. (arXiv:1810.12373v1 [cond-mat.mtrl-sci])

2018-10-31T02:29:13+00:00October 31st, 2018|Categories: Publications|Tags: , |

Recently, silicene, the graphene equivalent of silicon, has attracted a lot of attention due to its compatibility with Si-based electronics. So far, silicene has been epitaxy grown on various crystalline surfaces such as Ag(110), Ag(111), Ir(111), ZrB2(0001) and Au(110) substrates. Here, we present a new method to grow silicene via high temperature surface reconstruction of hexagonal IrSi3 nanocrystals. The h-IrSi3 nanocrystals are formed by annealing thin Ir layers on Si(111) surface. A detailed analysis of the STM images shows the formation of silicene like domains on the surface of some of the IrSi3 crystallites. We studied both morphology and electronic properties of these domains by using both scanning tunneling microscopy/spectroscopy and first-principles calculation methods.

Published in: "arXiv Material Science".

Shot noise in electrically-gated silicene nanostructures

2018-10-30T14:33:28+00:00October 30th, 2018|Categories: Publications|Tags: , |

We have theoretically studied fundamental shot noise properties in single- and dual-gated silicene nanostructures. It is demonstrated here that due to the intrinsic spin–orbit gap, the Fano factor ( F ) in the biased structures does not coincide with the characteristic value F = 1/3, a value frequently reported for a graphene system. Under gate-field modulations, the F in the gated structure can be efficiently engineered and the specific evolution of the F versus the field strength is symmetric with the center of spectra oppositely shifting away from the zero field condition for the valley or spin-coupled spinor states. This field-dependent hysteretic loop thus offers some flexible methods to distinguish one spinor state from its valley or spin-coupled state via their numerical difference in the F once the incident beam is spin or valley-polarized.

Published in: "Nanotechnology".

Spin and valley control in single and double electrostatic silicene quantum dots

2018-10-10T16:33:09+00:00October 10th, 2018|Categories: Publications|Tags: |

Author(s): Bartłomiej Szafran and Dariusz ŻebrowskiWe study quantum dots defined electrostatically in silicene. We determine the spin-valley structure of confined single- and two-electron systems, and quantify the effects of the intervalley scattering by the electron-electron interaction potential and the crystal edge. The double quantum dots are di…[Phys. Rev. B 98, 155305] Published Wed Oct 10, 2018

Published in: "Physical Review B".

Two-dimensional honeycomb borophene oxide: Strong anisotropy and nodal loop transformation. (arXiv:1810.03009v1 [cond-mat.mtrl-sci])

2018-10-09T02:29:27+00:00October 9th, 2018|Categories: Publications|Tags: , |

The search for topological semimetals is mainly focused on heavy-element compounds as following the footsteps of previous research on topological insulators, with less attention on light-element materials. However, the negligible spin orbit coupling with light elements may turn out to be beneficial for realizing topological band features.Here, using first-principles calculations, we propose a new two-dimensional light-element material-the honeycomb borophene oxide (h-B2O), which has nontrivial topological properties.The proposed structure is based on the recently synthesized honeycomb borophene on Al (111) substrate [Sci. Bull. 63, 282 (2018)]. The h-B2O monolayer is completely flat, unlike the oxides of graphene or silicene. We systematically investigate the structural properties of h-B2O, and find that it has very good stability and exhibits significant mechanical anisotropy. Interestingly, the electronic band structure of h-B2O hosts a nodal loop centered around the Y point in the Brillouin zone, protected by the mirror symmetry. Furthermore, under moderate lattice strain, the single nodal loop can be transformed into two loops, each penetrating through the Brillouin zone. The loops before and after the transition are characterized by different Z*Z topological indices. Our work not only predicts a new two-dimensional material with interesting physical properties, but also offers an alternative approach to search for new topological phases in 2D light-element systems.

Published in: "arXiv Material Science".

Ab initio quantum transport in AB-stacked bilayer penta-silicene using atomic orbitals

2018-10-03T10:32:15+00:00October 3rd, 2018|Categories: Publications|Tags: |

RSC Adv., 2018, 8,34041-34046DOI: 10.1039/C8RA05652H, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Eleni Chatzikyriakou, Padeleimon Karafiloglou, Joseph KioseoglouA methodology for parameter-free calculations of current density from first-principles using density functional theory, Wannier functions and scattering

Published in: "RSC Advances".

Influence of edge magnetization and electric fields on zigzag silicene, germanene and stanene nanoribbons. (arXiv:1810.00628v1 [cond-mat.mes-hall])

2018-10-02T04:30:59+00:00October 2nd, 2018|Categories: Publications|Tags: , , |

Using a multi-orbital tight-binding model, we have studied the edge states of zigzag silicene, germanene, and stanene nanoribbons (ZSiNRs, ZGeNRs and ZSnNRs, respectively) in the presence of the Coulomb interaction and a vertical electric field. The resulting edge states have non-linear energy dispersions due to multi-orbital effects, and the nanoribbons show induced magnetization at the edges. Owing to this non-linear dispersion, ZSiNRs, ZGeNRs and ZSnNRs may not provide superior performance in field effect transistors, as has been proposed from single-orbital tight-binding model calculations. We propose an effective low-energy model that describes the edge states of ZSiNRs, ZGeNRs, and ZSnNRs. We demonstrate that the edge states of ZGeNR and ZSnNR show anti-crossing of bands with opposite spins, even if only out-of-plane edge magnetization is present. The ability to tune the spin polarizations of the edge states by applying an electric field points to future opportunities to fabricate silicene, germanene and stanene nanoribbons as spintronics devices.

Published : "arXiv Mesoscale and Nanoscale Physics".

The Understanding of SiNR and GNR TFETs for Analog and RF Application With Variation of Drain-Doping Molar Fraction

2018-09-21T00:34:24+00:00September 21st, 2018|Categories: Publications|Tags: , , |

The 1-D nanoribbon (NR) of monolayer materials has gained immense interest due to their unique properties qualitatively distinct from their bulk properties and the demand for nanoscale applications. In this paper, the quantum transport properties of two most prominent 2-D materials, i.e., silicene NR (SiNR) and a graphene NR (GNR) tunnel field-effect transistor (TFET) with the effect of different dopant molar fractions in the drain region are studied numerically using nonequilibrium Green’s function formalism. In SiNR TFET, higher on-state current (${I}_{ mathrm{scriptscriptstyle ON}}$ ) is observed due to wider tunneling energy window and high transmission probability of carriers. In order to observe the effect of variation of doping density in the drain region, we have studied analog figures of merit such as the transconductance (${g}_{m}$ ), output resistance (${r}_{o}$ ), transconductance generation factor (${g}_{m}/{I}_{D}$ ), and the intrinsic gain (${g}_{m}{r}_{o}$ ) for different molar fractions. Similarly, we have evaluated the RF performance of the SiNR and GNR TFETs as a function of cutoff frequency (${f}_{T}$ ), gate capacitance (${C}_{G}$ ), and transport delay ($tau$ ).

Published in: "IEEE Transactions on Electron Devices".

Electronic transport and dynamical polarization in bilayer silicene-like system. (arXiv:1809.05983v1 [cond-mat.mes-hall])

2018-09-18T02:29:23+00:00September 18th, 2018|Categories: Publications|Tags: , |

We investigate the semiclassical electronic transport properties of the bilayer silicene-like system in the presence of charged impurity. The trigonal warping due to the interlayer hopping, and its effect to the band structure of bilayer silicene is discussed. Besides the trigonal warping, the external field also gives rise to the anisotropic effect of the mobility (at finite temperature) which can be explored by the Boltzmann theory. The dynamical polarization as well as the scattering wave vector-dependent screening within random phase approximation are very important in determining the scattering behavior and the self-consistent transport. We detailly discuss the transport behavior under the short- or long-range potential. The phonon scattering with the acoustic phonon mode which dominant at high temperature is also studied within the density functional theory (DFT). Our results are also valid for the bilayer graphene or bilayer MoS$_{2}$, and other bilayer systems with strong interlayer coupling.

Published in: "arXiv Material Science".

Orbital projected quantum transport in AB-stacked bilayer penta-silicene. (arXiv:1809.03477v1 [cond-mat.mtrl-sci])

2018-09-11T02:29:16+00:00September 11th, 2018|Categories: Publications|Tags: |

A novel methodology for quantum transport calculations from first principles that can be applied to nanoscale materials used for electronic device engineering is presented. The methodology is used to simulate quantum transport on free-standing AB-stacked bilayer penta-silicene. This new Si allotrope has been proposed to have a higher stability than any of its hexagonal bilayer counterparts. Furthermore, its semiconducting properties make it ideal for use in electronic components. We unveil the role of the pz orbitals in the transport through the quantum wire using Density Functional Theory calculations, Wannier functions and the Landauer formula with the use of scattering matrices. This work reveals the great potential of from first-principles calculations for studies of extremely scaled device configurations and the novel phenomena that arise at the atomic scale and can be expanded to accommodate many electron degrees of freedom.

Published in: "arXiv Material Science".

Optical properties of excitons in buckled two-dimensional materials in an external electric field

2018-09-07T14:33:38+00:00September 7th, 2018|Categories: Publications|Tags: , , |

Author(s): Matthew N. Brunetti, Oleg L. Berman, and Roman Ya. KezerashviliWe study the binding energies and optical properties of direct and indirect excitons in monolayers and double-layer heterostructures of Xenes: silicene, germanene, and stanene. It is demonstrated that an external electric field can be used to tune the eigenenergies and optical properties of excitons…[Phys. Rev. B 98, 125406] Published Fri Sep 07, 2018

Published in: "Physical Review B".

Characterization of epitaxial silicene with Raman spectroscopy

2018-08-30T16:33:52+00:00August 30th, 2018|Categories: Publications|Tags: , |

Author(s): G. Kukucska, V. Zólyomi, and J. KoltaiSilicene, the silicon equivalent of graphene, is most commonly grown on Ag(111) substrates where it undergoes reconstruction due to the strong interaction between the Si and Ag atoms. We demonstrate through first-principles density functional theory for eight reconstructions that the Raman spectrum …[Phys. Rev. B 98, 075437] Published Thu Aug 30, 2018

Published in: "Physical Review B".

Fully spin-polarized current in gated bilayer silicene

2018-08-28T14:34:19+00:00August 28th, 2018|Categories: Publications|Tags: |

Author(s): Xiao-Fang Ouyang, Ze-Yi Song, and Yu-Zhong ZhangBy applying density functional theory calculations, we predict that the ground state of bilayer silicene at certain interlayer distances can be antiferromagnetic. At small electron or hole doping, it becomes half metallic under applied out-of-plane electric field, which can be used to produce a full…[Phys. Rev. B 98, 075435] Published Tue Aug 28, 2018

Published in: "Physical Review B".

Tuning the mechanical properties of silicene nanosheet by auxiliary cracks: a molecular dynamics study

2018-08-28T14:32:56+00:00August 28th, 2018|Categories: Publications|Tags: |

RSC Adv., 2018, 8,30354-30365DOI: 10.1039/C8RA04728F, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.Shahriar Muhammad Nahid, Shahriar Nahian, Mohammad Motalab, Tawfiqur Rakib, Satyajit Mojumder, Md Mahbubul IslamInclusion of auxiliary cracks increases the fracture stress of silicene

Published in: "RSC Advances".

Many-electron effect to the dynamical polarization of silicene-like two-dimension Dirac materials. (arXiv:1808.06263v1 [cond-mat.mtrl-sci])

2018-08-21T02:29:28+00:00August 21st, 2018|Categories: Publications|Tags: , |

We discuss the dynamical polarization with finite momentum and frequency in the presence of many-electron effect, including the screened Coulomb interaction, self-energy and vertex correction. The longitudinal conductivity, screened Coulomb interaction, and the response function are calculated. The behavior of the Dirac Fermions, including the propagation of the charge density which exhibits the causality, affects largely the low-temperature physical properties of the Dirac semimetal, like the silicene. For the polarization-related quantities (like the dielectric function), the method of standard random phase approximation (RPA) provides the non-interaction results (ignore the many electron effect), for a more exact result, we discuss the self-energy and the vertex correction for the two-dimension Dirac model. We found that, after the self-energy correction, the longitudinal conductivity increase compared to the noninteracting one in optical limit. For the renormalization treatment, the ultraviolet cutoff is setted as $Lambda=t$ in our calculations, i.e., within the range between two Van Hove singularities where the density of states divergent logarithmically. %The $Lambda$ is indeed a non-universal parameter and can also be choiced larger than arbitary ${bf q}$ or $omega$. The (corrected) screened Coulomb interaction and the response function are also discussed. Our results are helpful to the application of the Dirac materials (or the Weyl semimetal) in spintronics or valleytronics.

Published in: "arXiv Material Science".

Electron spin inversion in gated silicene nanoribbons

2018-08-15T16:33:20+00:00August 15th, 2018|Categories: Publications|Tags: , |

Author(s): Bartłomiej Rzeszotarski and Bartłomiej SzafranWe study locally gated silicene nanoribbons as spin active devices and we solve the quantum scattering problem in the atomistic tight-binding formalism. Particular attention is paid to the low energy range for which only four subbands appear at the Fermi level. We find that the gated segments of zig…[Phys. Rev. B 98, 075417] Published Wed Aug 15, 2018

Published in: "Physical Review B".

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