arXiv subjects

Shoeib Babaee Touski

Publications and source records attributed to Shoeib Babaee Touski.

16 recordsLinked to original sources

arXiv2022

Hydrogen Storage Performance Enhancement and Bandgap Opening of M-Decorated ($\mathrm{M}=\mathrm{Li}$, Na and K) III\textsubscript{4}-V\textsubscript{4} Monolayer by Fluorine Functionalization

The effects of fluorine functionalization on the hydrogen storage capability of alkaline decorated III\textsubscript{4}-V\textsubscript{4} monolayers is studied. This structure can store up to two hydrogen molecules per alkaline atom. Here, we demonstrate that functionalizing alkaline decorated monolayer with a high electronegative element of fluorine can significantly enhance both binding energy and the maximum number of the stored hydrogen molecules. In this regard, the hydrogen molecule storage capability is notably improved from two to four and when absolute binding is considered. In addition, F-functionalization of M-decorated III\textsubscript{4}-V\textsubscript{4} can demonstrate bandgap opening effect, introduce semiconducting characteristics and forming a new two-dimensional semiconductor structure. The bandgap for Li-Al$_4$P$_4$-F is 1.23 eV which is very close to the solar peak. The resulted bandgap in the M-III\textsubscript{4}-V\textsubscript{4}-F structure is even significantly larger than that of pristine III\textsubscript{4}-V\textsubscript{4} monolayer. The binding of the hydrogen molecule to the alkaline atom is also improved from 0.114 to 0.272 eV by the fluorine functionalization.

cond-mat.mtrl-sci↗

arXiv2021

Field-Effect Transistor Based on MoSi$_2$N$_4$ and WSi$_2$N$_4$ Monolayers Under Biaxial Strain: A Computational Study of the Electronic Properties

The electronic properties of a field-effect transistor with two different structures of MoSi$_2$N$_4$ and WSi$_2$N$_4$ monolayers as the channel material in the presence of biaxial strain are investigated. The band structures show that these compounds are semiconductors with an indirect bandgap. Their band gaps can be adjusted by applying in-plane biaxial strain. In the following, the variation of the energies of the valleys and corresponding effective masses with respect to the strain are explored. Finally, the strained MoSi$_2$N$_4$ or WSi$_2$N$_4$ are used as the channel of a p-type FET and the corresponding current-voltage characteristic is explored. The results show this FET has an I$\mathrm{_{ON}}$/I$\mathrm{_{OFF}}$ ratio larger than $\mathrm{10^6}$ and subthreshold swing in the range of 96-98 mV/dec. The I$\mathrm{_{ON}}$/I$\mathrm{_{OFF}}$ ratio of these compounds with respect to strain are compared.

cond-mat.mtrl-sci↗

arXiv2021

Vertical Strain-Induced Modification of the Electrical and Spin Properties of Monolayer MoSi2X4 (X= N, P, As and Sb)

In this work, the electrical and spin properties of monolayer MoSi2X4 (X= N, P, As, and Sb) under vertical strain are investigated. The band structures state that MoSi2N4 is an indirect semiconductor, whereas other compounds are direct semiconductors. The vertical strain has been selected to modify the electrical properties. The bandgap shows a maximum and decreases for both tensile and compressive strains. The valence band at K-point displays a large spin-splitting, whereas the conduction band has a negligible splitting. On the other hand, the second conduction band has a large spin-splitting and moves down under vertical strain which leads to a large spin-splitting in both conduction and valence bands edges. The projected density of states along with the projected band structure clarifies the origin of these large spin-splittings. These three spin-splittings can be controlled by vertical strain.

cond-mat.mtrl-sci↗

arXiv2021

Structural and Electrical Properties of Bilayer SiX (X= N, P, As and Sb)

In this work, the structural, electrical, and optical properties of bilayer SiX (X= N, P, As, and Sb) are studied using density functional theory (DFT). Five different stacking orders are considered for every compound and their structural properties are presented. The band structure of these materials demonstrates that they are indirect semiconductors. The out-of-plane strain has been applied to tune the bandgap and its electrical properties. The bandgap increases with tensile strain, whereas, compressive strain leads to semiconductor-to-metal transition. The sensitivity of the bandgap to the pressure is investigated and bilayer SiSb demonstrates the highest bandgap sensitivity to the pressure. These structures exhibit Mexican hat-like valence band dispersion that can be approved by a singularity in the density of states. The Mexican-hat coefficient can be tuned by out-of-plane strain. Optical absorption of these compounds shows that the second and lower valence bands due to the high density of states display a higher contribution to optical transitions.

cond-mat.mtrl-sci↗

arXiv2020

The Effects of vertical electric field and charged impurities on the spin-polarized transport of $β$-antimonene armchair nanoribbons

The electronic properties of antimonene, single-layer Sb, are attracting great attention. In this paper, spin transport in armchair antimonene nanoribbon (ASbNR) is investigated. Following the tight-binding model, we calculate both the transmission probability and the conductance by means of the non-equilibrium Green's function (NEGF) method. The effects of an external electric field vertical to the ribbon plane are explored. Our results indicate that the spin-flip rate increases with the vertical electric field. Disorder effects on spin transport are addressed by considering the presence of charged impurities. It is found that charged impurities also enhance the spin-flip rate but to a lesser extent than the out-of-plane electric field.

cond-mat.mes-hall↗

arXiv2020

The Electrical and Spin Properties of Monolayer and Bilayer Janus HfSSe under Vertical Electrical Field

In this paper, the electrical and spin properties of mono- and bilayer HfSSe in the presence of a vertical electric field are studied. The density functional theory is used to investigate their properties. Fifteen different stacking orders of bilayer HfSSe are considered. The mono- and bilayer demonstrate an indirect bandgap, whereas the bandgap of bilayer can be effectively controlled by electric field. While the bandgap of bilayer closes at large electric fields and a semiconductor to metal transition occurs, the effect of a normal electric field on the bandgap of the monolayer HfSSe is quite weak. Spin-orbit coupling causes band splitting in the valence band and Rashba spin splitting in the conduction band of both mono- and bilayer structures. The band splitting in the valence band of the bilayer is smaller than a monolayer, however, the vertical electric field increases the band splitting in bilayer one. The stacking configurations without mirror symmetry exhibit Rashba spin splitting which is enhanced with the electric field.

cond-mat.mtrl-sci↗

arXiv2020

Ultra-Thin SiGe in the Source Modifies Performance of Thin-Film Tunneling FET

In this work, the source structure of an n-type thin-film tunneling FET is engineered to get better performance. An ultra-thin SiGe along with Si is used in the source of silicon-based TFET. Two structures are compared with conventional TFET, one, SiGe is located on the top of Si in the source and another one in reverse. Simulations approve these structures can reduce sub-threshold swing, OFF-current several times, and increase the ON-OFF ratio. Band diagram for conduction and valance bands are investigated and band to band tunneling (BTBT) generation rate is used to find better performance. We find current flows at Si in the source with the wider bandgap. Ge mole fraction of SiGe is varied and its effects on the performance of TFET are studied. The SiGe thickness for both structures is explored to obtain the best thickness for SiGe.

cond-mat.mes-hall↗

arXiv2020

Spin-Orbit and Strain Induced Modification in Electrical Properties of Monolayer InSb

In this work, the electrical properties of monolayer InSb in the presence of biaxial strain using density functional theory are investigated. Here, we first explore the band structure of InSb with and without spin-orbit coupling (SOC) consideration. The electron and hole effective mass modify with SOC consideration. The electron and hole effective masses lowered two and ten times, respectively. The location of valleys in conduction and valence band for various strains are explored, and the corresponding effective masses are reported. A lower effective mass is obtained for both electron and hole with applying tensile strain, whereas, the bandgap closes for large tensile strain. A numeric fitting has applied to effective mass versus strain, and an equation for every curve is reported. Finally, the work function of this material for different strains is obtained.

cond-mat.mes-hall↗

arXiv2020

Interplay Between Stacking Order and In-plane Strain on the Electrical Properties of Bilayer Antimonene

In this work, the electrical properties of bilayer Antimonene with different stacking orders are studied. Density functional theory with van der Waals (vdW) correction is used to investigate the electrical performances. Two configurations demonstrate considerable bandgaps, whereas, the bandgaps are close to zero for other structures. The in-plane biaxial strain is applied to modify the electrical properties. The bandgap reaches a maximum at a specific strain level and then closes at more enormous compressive and tensile strains. The energy of three valleys ($Γ$, Q, and K) in the conduction band are explored with the strain. The conduction band minimum switches between these valleys with the strain. Two bands also contribute to the valence band maximum, and the energy of these two bands for various strains is investigated. Finally, the effective mass for the valleys of the conduction band and the valence band are obtained. The effective mass at $Γ$-valley demonstrates the lowest effective mass.

cond-mat.mtrl-sci↗

arXiv2020

Strain Engineering of Spin and Rashba properties in Group-III Monochalcogenide MX (M=Ga, In and X=S, Se, Te) Monolayer

In this paper, spin properties of monolayer MX (M=Ga, In and X=S, Se, Te) in the presence of strain are studied. Density functional theory is used to investigate spin properties. The strain changes modification of bandgap due to spin-orbit coupling, the results indicate the spin-orbit coupling has a higher effect in the compressive regime. Also, spin splitting in the conduction and valence bands respect to strain are compared for six materials. The location of conduction band minimum (CBM) imposed a type of spin properties. These materials with mirror symmetry can display the Rashba effect while M valley is located at CBM. Strain tunes the conduction band minimum in three valleys (K, M and $Γ$ valleys) and determines which spin effect (spin splitting, Rashba splitting or no spin splitting) has occurred in each strain for every material. Lastly, the relation between the Rashba parameter and the atomic mass is explored and it is observed that there is a linear correlation between atomic mass and Rashba coefficient.

cond-mat.mtrl-sci↗

arXiv2019

Spin Relaxation at Graphene Nanoribbons in the presence of Substrate Surface Roughness

In this work spin transport in corrugated armchair graphene nanoribbons (AGNR) is studied. We survey combined effects of spin-orbit interaction and surface roughness, employing the non-equilibrium Green's function formalism and four orbitals tight-binding model. We modify hopping parameters regarding bending and distance of corrugated carbon atoms. The effects of surface roughness parameters, such as roughness amplitude and correlation length, on the spin transport of the graphene nanoribbons are studied. We show that increasing surface roughness amplitude breaks the AGNR symmetry and hybridize $\mathitσ$ and $\mathitπ$ orbitals, leading to more spin flipping and therefore decrease in polarization. Unlike the roughness amplitude, the longer correlation length makes AGNR surface smoother and increases polarization. Moreover, the Spin diffusion length of carriers is extracted and its dependency on the roughness parameters is investigated. We find the spin diffusion length for various surface corrugation amplitudes in order of 1 to 80 micrometers.

cond-mat.mes-hall↗

arXiv2019

A Comparative Study of Substrates Disorder on Mobility in the Graphene Nanoribbon: Charged Impurity, Surface Optical Phonon, Surface Roughness

The effects of substrate on the electronic properties of Graphene remains unclear. Many theoretical and experimental efforts have been done to clarify this discrepancy. In this work, we studied the electronic transport in armchair Graphene nanoribbons (AGNR) in the presence of substrate's disorder. The three main substrate's disorders -- surface roughness, charged impurity and surface optical phonon -- are investigated. Non-Equilibrium Green's function along with the tight-binding model is employed to investigate the electronic properties of Graphene Nanoribbons. The effects of these disorders are investigated individually, finally, the effects of them are compared to determine the dominant source of scattering.

cond-mat.mes-hall↗

arXiv2019

Electrical and ELectronic Properties of Strained Mono-layer InTe

In this paper, electrical and electronic properties of strained mono-layer InTe for two structures, $α$, and $β$ phases, is investigated. The band structure is obtained using density functional theory (DFT). The minimum energy and effective mass of the conduction band and second conduction band for different strains are calculated. A FET with using InTe as the channel material is investigated. Voltage-current characteristics of InTe FET is calculated and I$_{ON}$/I$_{OFF}$ ratio is obtained with respect to biaxial strain.

cond-mat.mes-hall↗

arXiv2019

Spin-Splitting and Rashba-Effect at Mono-Layer GaTe in the Presence of Strain

In this paper, spintronic properties of the mono-layer GaTe under biaxial and uniaxial strain is investigated. Here, spin properties of two structures of GaTe, one with mirror symmetry and the other with inversion symmetry, is studied. We have also calculated the band structure of GaTe with and without spin-orbit coupling to find out the importance of spinorbit interaction (SOI) on its band structure. We find band gap can be modified by applying spin-orbit coupling in the presence of strain. We explore Mexican-hat dispersion for different structures and different strain. We find Mexican-hat can be tuned however some cases shows any Mexican-hat. We calculate spin-splitting in conduction and valence band in the presence of strain where the structure with inversion symmetry doesn't show any splitting. We find in some cases, GaTe indicates Rashba dispersion that can be adjusted by strain. The amount of Rashba parameters may be in the order of other reported two-dimensional materials.

cond-mat.mtrl-sci↗

arXiv2019

Spin Transport in Armchair Silicene Nanoribbon on the Substrate: The Role of Charged Impurity

In this work, electrical and spin properties of armchair silicene nanoribbon (ASiNR) in the presence of charged impurity is studied. The non-equilibrium Green's function along with multi-orbital tight-binding is applied to obtain transmission probability. different type of spin transmission probability in the ASiNR on a substrate is investigated. The charged impurities are located in the underlying substrate. Spin-flip along the channel is calculated by using spin transmission probability. Spin diffusion length in ASiNR for differently charged impurities is obtained and compared with the mean free path

cond-mat.mes-hall↗

arXiv2017

Enhanced Spin-Flip Scattering by Surface Roughness in WS$_2$ and MoS$_2$ Armchair Nanoribbons

The band structures of single-layer MoS$_2$ and WS$_2$ present a coupling between spin and valley degrees of freedom that suppresses spin-flip scattering and spin dephasing. Here we show that out-of-plane deformations, such as corrugations or ripples, enhance spin-flip scattering in armchair MoS$_2$ and WS$_2$ nanoribbons. Spin transport in the presence of surface roughness is systematically investigated, employing the non-equilibrium Green's function method along with the tight-binding approximation. Both transmission and conductance have been calculated as a function of surface roughness. Our results indicate that the spin-flip rate, usually neglected in flat pristine samples, increases significantly with the surface roughness amplitude. These results are important for the design and fabrication of transition metal dichalcogenides based spintronic devices.

cond-mat.mes-hall↗