Silicene Nanoribbons Research Articles

Study of Antimony‐Doped Silicene Nanoribbons in the Electric Field

AbstractSilicene is a structure made of silicon atoms with a honeycomb hexagonal configuration. Silicene is not a flat structure like graphene, it has buckling. Silicene nanoribbons (SiNRs) are low‐dimensional structures built from silicene with chemically modified edges. The electronic properties of SiNRs also depend on the modification elements at the two edges. The antimony element will be doped in the SiNRs, and the electric field acting on the system is a constant electric field 0.3 V Å‐1. The configurations are stable after optimization by density function theory (DFT), and the energies of formation of the systems will also be calculated. The energy bands, states of the configurations will be plotted, analyzed, and compared. The structures after doping are all semi‐metallic, the band gap has disappeared. The partial states are also investigated, which depends on the density of particles per unit cell.

Performance analysis of fluorinated silicene based magnetic tunnel junction

Two-dimensional material based Spintronic devices are considered to be the promising next generation nano-electronic devices due to their low power, high speed and enhanced data storage capabilities. In this work, firstly we have investigated the effect of fluorination on the electronic/structural properties of zigzag/armchair silicene. Next, we have modelled a magnetic tunnel junction (MTJ) device consisting of CrO2 electrodes and fluorine passivated armchair silicene nanoribbon as scattering region. The spin dependent transport properties are calculated via first principles calculations combined with non-equilibrium Green's function formalism. The modeled MTJ device shows very large magnetoresistance as compared to the state of art reported devices and high spin injection efficiency. The spin-dependent transmission spectrum and density of states were calculated to elucidate the obtained transport characteristics.

Pristine and modified silicene based volatile organic compound toxic gas sensor: a first principles study

In this work, we have investigated the sensitivity of two Volatile Organic Compounds (VOCs), formaldehyde (FD) and acetaldehyde (AD) on the surface of two-dimensional (2D) Armchair Silicene Nanoribbon (ASiNR) by analysing the structural, electronic and transport properties using density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalism. Different models of ASiNR have been considered viz; pristine, Al-doped, P-doped, Al/P co-doped and vacancy-defected ASiNR. The findings revealed that the vacancy-defected models shows a significant increase in the adsorption energies for both VOCs compared to other models. Apart from that, in all the models, the current increases with the applied voltage and the maximum value of current was found in Al/P co-doped model at a higher bias voltage of 2 V. The variation of the computed transmission spectrum peaks from −2 to 2 eV of energy values also confirms the sensitivity of the proposed models towards the VOC molecules. Moreover, the projected device density of states (PDDOS) revealed that all the models remain semiconducting before and after adsorption, which completely agrees with the transmission spectrum. Furthermore, Al/P co-doped model shows high sensitivity of 68% and77% towards FD and AD molecules respectively. Thus, it is concluded that the modeled ASiNR VOC gas sensors will aid in sensing cancer.

Electronic and Thermoelectric Properties of Armchair-Edge Silicene Nanoribbons: Role of Quantum Antidot Arrays

Electronic and Thermoelectric Properties of Armchair-Edge Silicene Nanoribbons: Role of Quantum Antidot Arrays

Electrical and optical properties of C, Ge-doped armchair silicene nanoribbons applied in optoelectronics

With the continuous development of nanotechnology, the search for new material structures plays a crucial role. Silicene nanoribbons (SiNRs) are one-dimensional materials that hold promise for numerous potential applications in the future. The electric and optical properties of C, Ge-doped armchair SiNRs are investigated in this study using density functional theory. All the doped configurations are stable and maintain the honeycomb hexagonal structure after optimization. Doping with C yields flatter structures, while doping with Ge yields larger buckling heights. The C 1–1 doping configuration is highlighted because its band gap is extended up to 2.35 eV, making it an ideal candidate for potential optoelectronic applications. The charge distribution, charge density difference, and hybridization of multiple orbitals are also systematically studied. The optical properties reveal the differences between C and Ge doping, with a clear anisotropy observed. Strong absorption occurs at high electromagnetic wave energies, while the absorption coefficient rapidly decreases in the long-wavelength range. The study of electron–hole density shows good agreement with the energy band structure, where electron–hole pairs only exist when the excitation energy is greater than the bandgap width, and not all excitation energy values give rise to electron–hole pairs. This study contributes a small part to creating potential applications in nanotechnology.

Research on the structural and electronic properties of silicene nanoribbon material adsorpted lithium

This paper presents these results of studying about the structure and electronic properties of armchair silicene nanoribbon materials (ASiNR), with pristine and as adsorbing a Li atom. The adsorpted positions investigated include “top”, “hollow”, “bridge” and “valley”. The results has shown that the optimal adsorption position is “hollow”. By the calculations of charge difference, the Bader charge, energy band structure, the orbitals in the ×, y, z directions. These results has shown that ASiNR has semiconducting properties, the band gap about 0.4 eV; ASiNR when adsorbing a Li in the “hollow” position, the structure again exhibits metallic properties, there is no longer any band gap energy.

First-principles study on adsorption of oxygen on H-terminated armchair silicene nanoribbon

This work systematically studies the electronic and optical properties of H-terminated armchair silicene nanoribbon (HASiNR) for oxygen (O2) adsorption using first-principles calculations. The results show that the most stable site for O2 adsorption is the edge of the ribbon, which possesses relatively low adsorption energy of −2.46[Formula: see text]eV, indicating good stability. Particularly, the adsorption energy decreases gradually with the increase of the oxygen concentration. It was also found that the direct bandgap of HASiNR can be effectively tuned by changing the adsorption concentration of O2 gas. Additionally, the analysis of the density of states shows that the adsorption of O2 on HASiNR is chemisorption due to the apparent charge transfer from the ribbon to O2 gas. Besides, the work function, absorption coefficient and refractive index of the HASiNR are sensitive to O2 gas adsorption. Therefore, our studies prove that oxygen gas adsorption allows the HASiNR to modulate its electronic and optical properties.

Role of Linear Defects on the Electronic, Transport, and Thermoelectric Properties of Armchair Edge Silicene Nanoribbons

Role of Linear Defects on the Electronic, Transport, and Thermoelectric Properties of Armchair Edge Silicene Nanoribbons

Hydrogenated cove-edge aluminum nitride nanoribbons for ultrascaled resonant tunneling diode applications: a computational DFT study

While synthesizing quasi-one-dimensional nanoribbons, there is a finite probability that edges have cove-edge defects. This paper focuses on the structural, electronic, and transport properties of cove-edge aluminum nitride nanoribbons (AlNNR) using density functional theory and the non-equilibrium Green’s function (NEGF) method. The cove-edge AlNNRs are thermodynamically stable and exhibit metallic behavior. Interestingly, the calculated current–voltage characteristics of the cove-edge AlNNR-based nanodevices show negative differential resistance (NDR). The H-AlN-Cove nanodevice exhibits high peak-to-valley current ratio (PVCR) of the order of 107. The calculated PVCR of the H-AlN-Cove nanodevice is 106 times higher than that of the silicene nanoribbon (SiNR) and graphene nanoribbon (GNR), and 104 times higher than that of the phosphorene nanoribbon (PNR) and arsenene nanoribbons (ANR)-based devices respectively. The NDR feature with high PVCR provides a prospect for the cove-edge AlNNR in nanodevice applications.

Molecular dynamics study of the finite-size effect in 2D nanoribbon silicene

ABSTRACT We present the molecular dynamics (MD) simulation of the finite-size effect in 2D silicene nanoribbons (SiNRs). Five silicene nanoribbon structures were modelled with the same length and buckling, but different width sizes. All models were melted from the perfect honeycomb silicene structure and then cooled from the disordered liquid state. Structural properties such as ring sizes, radial distribution function, coordination numbers, and interatomic distances have been carefully analysed. All models’ critical melting and cooling temperature were determined via total energy per atom. We found that 2D SiNRs transition temperature is lower than the pristine silicene. Particularly, the SiNRs present a noticeable finite-size effect on nanoribbons, resulting in a domain-type structure of 4, 5, and 6-fold rings.

Effects of Stone-Wales and applied electric fields on the structure and electrical properties of silicene nanoribbons by SCC-DFTB calculations

Effects of Stone-Wales and applied electric fields on the structure and electrical properties of silicene nanoribbons by SCC-DFTB calculations

Switching modulation of spin transport in ferromagnetic tetragonal silicene

We study the band structure and transport properties of ferromagnetic tetragonal silicene nanoribbons by using the non-equilibrium Green's function method. The band structure and spin-dependent conductance are discussed under the combined effect of the external electric field, potential energy, exchange field and the spin-orbit coupling. One can easily realize a phase transition from a semimetallic to a semiconducting state by changing the transverse width of the nanoribbon. Separation of spin-dependent conductances arises from the effect of exchange field and the spin-orbit coupling, while zero-conductance behaviors exhibit spin-dependent band gaps induced by the electric field. We propose a device configuration of four-terminal tetragonal silicene nanoribbon with two central channels. It is found that spin current can be controlled by utilizing two switches. The switch with a high potential barrier can block electrons flowing from the central scattering region into other terminals. Interestingly, applying only one switch can realize spin-dependent zero conductance and large spin polarization. Two switches can provide multiple operations for controlling spin-dependent transport properties. The two-channel ferromagnetic tetragonal silicene nanoribbon can realize an effective separation of spin current, which may be a potential candidate for spintronic devices.

Tuning the thermoelectric properties of doped silicene nanoribbon heterostructures

In this work, we investigate the thermoelectrical properties of a silicene nanoribbon heterostructure composed of a central conductor fully doped with ad-atoms and connected to two pristine leads of the same material. Using a tight-binding Hamiltonian, we have calculated the system’s thermoelectric properties as a function of the geometrical confinement and external field. Our results exhibit an enhancement of the thermopower when a transverse electric field is applied to the conductor region for different temperatures. In addition, a violation of the Wiedemann–Franz law is observed around the ad-atom energy. Our results suggest the thermoelectric properties of doped silicene nanoribbons can be efficiently tuned with external perturbations.

Controllable Low-Bias Rectifying Behaviors Induced by AA-P2 Dopants in Armchair Silicene Nanoribbons with Different Widths

The electronic transport properties and rectifying behaviors of armchair silicene nanoribbons (ASiNRs) were investigated by using first-principles density functional theory, in which the left lead was pristine ASiNR and the right lead was doped ASiNR where two phosphorus (P) atoms replaced a pair of adjacent silicon atoms in the same sublattice A (AA-P2). Two types of AA-P2-doped models were considered for P dopant-substitute silicon atoms at the center or edges. The results showed that the rectification behavior of the system with a large rectifying ratio could be found, which could be modulated by changing the width of the silicene nanoribbons or the position of the AA-P2 dopant. Mechanisms were revealed to explain the rectifying behaviors and provide a theoretical basis for semiconductor rectifier devices.

Molecular dynamics simulation of pressure effect on silicene nanoribbons

Molecular dynamics simulation of pressure effect on silicene nanoribbons

Enhanced thermoelectric efficiency in armchair silicene nanoribbons decorated by Mn

In this study, we use density functional theory to investigate the structural stability as well as the magnetic and thermoelectric properties of Mn-passivated armchair silicene nanoribbons (Mn-ASiNRs). All structures considered in this study were thermodynamically stable, and existed in ferromagnetic ground states with a Curie temperature greater than 400 K. The Mn-ASiNRs showed spin-polarized electronic properties that were tunable with respect to their width (N). Mn-ASiNRs with N = 4, 5, and 7 (4-, 5- and 7-Mn-ASiNRs) were semiconducting, while 6-Mn-ASiNR was half-metallic and 8-Mn-ASiNR was metallic. We simulated N-Mn-ASiNR-based devices to evaluate their thermoelectric properties, and observed a high-spin Seebeck coefficient (SS) of 1800 μV/K at μ=0 and a charge Seebeck coefficient (SC) of 1350 μV/K at μ=−0.17 eV for 4-Mn-ASiNRs. We obtained significantly enhanced charge and spin thermoelectric figures of merit (ZCT and ZST) compared with those of pristine nanoribbons (H-ASiNRs) that had maximum values of 25 and 18 at room temperature for 4- and 7-Mn-ASiNRs, respectively. ZCT and ZST further improved to values of 150 and 190, respectively, at temperatures lower than 100 K owing to a rapid increase in SC and SS, and exhibited decreased thermal conductance (Kt). Moreover, we showed that a thermally driven spin current with a negligibly small charge current can be generated by our devices. The results of this theoretical study indicate that Mn-ASiNR can be used to develop effective thermoelectric energy conversion devices.

Highly Thermoelectric Efficient Armchair Silicene Nanoribbons With Silicon Adatom Defects

In this work, we propose armchair silicene nanoribbons with silicon (Si) adatom defect (ASiNR-Ad) for efficient thermoelectric devices. Using density functional theory (DFT) and nonequilibrium Green’s function method, we investigated the spin caloritronic effect on ASiNR-Ad of different widths ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}={4}$ </tex-math></inline-formula> , 5, 6, and 7). We observed that all ASiNR-Ads are magnetic semiconductors with a variable spin gap. Our results showed that the presence of adatom defect on armchair silicene nanoribbons (ASiNRs) significantly lowers phonon thermal conductance at ambient temperature. The ASiNR-Ads also exhibit large spin and charge Seebeck coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}_{s}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}_{c}$ </tex-math></inline-formula> ) values of 1200 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1120 ~\mu \text{V}$ </tex-math></inline-formula> /K, respectively. The large value of Seebeck coefficients and reduced phonon thermal conductance results in the high value of spin and charge thermoelectric figure of merit ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z}_{s}{T}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z}_{c}{T}$ </tex-math></inline-formula> ) of ~64 and ~58, respectively, in the narrow device which is substantially higher than pristine ASiNRs having a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z}_{s}{T}={0}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z}_{c}{T}={2.8}$ </tex-math></inline-formula> . Spin current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{s}$ </tex-math></inline-formula> ) dominates charge current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{c}$ </tex-math></inline-formula> ) in all the considered devices. A zero charge current was achieved by modulating temperature drop across the ASiNR-Ad based device, thus eliminating the Joule heating effect. Moreover, we observed an unprecedented giant thermal magnetoresistance (MR) of ~ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4.3}\times{10}^{{6}}\%$ </tex-math></inline-formula> in the ASiNR-Ad based device. These findings suggest that ASiNR-Ad can be employed effectively for energy harvesting and low-power applications utilizing spin current.

Effects of edge hydrogenation and applied electric field on the structure and electrical properties of zigzag silicene nanoribbons by SCC-DFTB calculations

The effects of edge hydrogenation and applied electric field in different directions on the geometrical structure and electrical properties of zigzag silicene nanoribbons (ZSiNRs) with different period widths (width = 2,3,4) were investigated by using a self-consistent charge density functional tight-binding (SCC-DFTB) method. The results show that the degree of warpage of the ZSiNRs is significantly changed by hydrogenation, while the bond length and bond angle are less affected. The edge hydrogenation reduces the Si-dangling bonds in the nanoribbons, which increased the binding energy of nanoribbon and enhanced system stability. In the absence of an electric field, the unhydrogenated nanoribbons with different period widths all exhibit semiconducting properties, and the hydrogenated nanoribbons exhibit metallic or semi-metallic properties. Under the vertical external electric field in the z-direction, the stability and energy gap of the unhydrogenated nanoribbons are sensitive to the change of strength, and the oscillation fluctuation is large. With the increase of strength, the atoms in the outermost four layers of the nanoribbons show obvious charge gain and loss. When the vertical electric field is applied to the hydrogenated nanoribbons, the energy gap changes are related to the period width. Their electrical properties realized the conversion between the semi-metal properties and the direct band gap semiconductor properties. Charge transfer occurs between the adjacent two layers of atoms. Under the same electric field strength, the amount of charge transfer increases from left to right along the direction of the width of the nanoribbon; at the same time, with the increase of the electric field strength, the amount of charge transfer also presents an increasing trend.

Study of Cu-doped silicene nanoribbons in the electric field

This work studies copper doping in silicene nanoribbons. The electric field acting on the system has a constant magnitude of 0.4V/Å. The unit lattice studied here consists of twelve silicon atoms and four hydrogen atoms in one unit cell, hydrogen atoms to modify two edges. There are two doped structures studied, the top stucture and the valley structure, each with one substitution doped Cu atom per unit cell. The theory used to study computation here is density functional theory (DFT). The formation energies, state bands and energy regions of the doped system are calculated and plotted. Thanks to the copper doping process and the influence of the electric magnetic field, the system after doping becomes semi-metallic. The top doped structure shows more optimization and stability. In the quest to find new materials with features that match the requirements of practice, this is a promising study. This study lays the groundwork for future applications in electronic technology.

DFT Analysis of Hydrogenated Zigzag Aluminum Nitride Nanoribbons for Spintronic Devices

Density functional theory (DFT) and nonequilibrium Green’s function (NEGF) framework are used to explore the structural, spin-polarized electronic, and spin-based transport properties of edge-hydrogenated zigzag aluminum nitride nanoribbons (ZAlNNRs). The proposed ZAlNNR is observed to be structurally stable and exhibits half-metallic nature in the magnetic state. The quantum transport property of the proposed two-terminal device model of 1H-AlN-1H demonstrates the bipolar spin-filter characteristics along with giant magnetoresistance (GMR), spin-based peak to valley current ratio (spin-PVCR), and spin-based rectification ratio (spin-RR) of the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> , 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> , and 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> , respectively. The calculated GMR and spin-RR of the 1H-AlN-1H device are 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> and 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> times higher than zigzag silicene nanoribbon (ZSiNR) and doped-zigzag graphene nanoribbon (doped ZGNR), respectively. The observed GMR, spin-PVCR, and spin-rectifying behavior of the reported ZAlNNR device could be deployed for multifunctional spintronic device applications.