Armchair Silicene Nanoribbons Research Articles

Applying the first principle to study the structure, electrical and magnetic properties of ASiNRs-doped Neodymium

In this project, we investigated and investigated the optimal sites in the chemisorption of Neodymium (Nd) on armchair silicene nanoribbons (ASiNRs) to learn about the geometrical and electronic properties of the structures by applying these properties with first principle math. The survey has three steps. The first was to change the top, valley, bridge, and hollow positions to find optimazed positionThe results show that the Bridge position has the lowest absorbed energy value of -2.6eV, has the most stable structure, with the strongest magnetic moment of 4.68 μB, and a buckl degree of 0.69 Å; The Si-Si-Si bond angle at this time is 115053’ almost like the pristine case. The second was to change the Si-Si bondlength of ASiNRs the same purpose. Finally, we survey the distance from Nd atom to pristine adsorbent surface was decreased. The calculation results show that the valley position is the most ideal location, corresponding to the bond length of 2.26 Å and the optimal height of 2.11 Å resulting in a single material adsorption system for the new materials, different from other positions with bandgap changed. This result shows that the absorption method between metals and pristine semiconductor ASiNRs has opened up a very good direction, contributing to enriching the source of materials applied to the field of manufacturing electronic, optoelectronic, and spintronic components in the future.

DFT Calculations on Defect Induced and Doped ASiNR for Sensing the COPD Breath Biomarker

COPD is a respiratory disease with a high mortality rate worldwide. The major cause of death in COPD patients is due to late diagnosis. Early detection of COPD is crucial for significantly reducing the risk of death but is challenging to attain. A distinguished way to early diagnosis is by using the nanosensor for sensing the COPD breath biomarkers. For the first time, we report an armchair silicene nanoribbon (ASiNR) as a promising sensing material for the diagnosis of hexanal a COPD breath biomarker. In this present study, the density functional theory (DFT) with Grimme D2 corrected approach was incorporated to observe the ground state electronic properties and adsorption mechanism of hexanal on the pristine, defect induced (D) and B, C, and N-doped ASiNR systems. N-ASiNR systems show the highest adsorption energy value among previously reported works due to the presence of strong covalent interaction, and it does not show recovery at room temperature. The B-ASiNR system with higher charge transfer exhibits large work function change with the fastest recovery at room temperature in 1.81 s. Our results confirms B-doped ASiNR system acts as an efficient reusable work function-based sensor for the early diagnosis of COPD at room temperature.

Simulation of the Xenes nanoribbons for sensing CO, CO2, and CH4 gases

Xenes emerge as promising materials for sensing applications. The capabilities of armchair Graphene, Silicene, and Phosphorene nanoribbons (AGNR, ASiNR, and APNR) as gas sensors have been investigated using tight-binding approximation and non-equilibrium Green’s function approach. These Xenes have been used for sensing CO, CO2, and CH4 at different concentrations. The results revealed that the AGNR has an excellent sensitivity and selectivity to CO and CO2 gases than other sensors. Although ASiNR has considerable sensitivity to CO and CH4 gas molecules at all concentrations, it can select CO from others. The APNR just can detect CO2 gas molecules and shows poor selectivity, furthermore, it has shorter recovery time than AGNR and ASiNR, due to gas-Xene bond type.

Effect of Vertical Magnetic Field on the Electronic and Transport Properties of Armchair Silicene Nanoribbons

Effect of Vertical Magnetic Field on the Electronic and Transport Properties of Armchair Silicene Nanoribbons

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.

Non-equilibrium Green’s function approach for simulation asymmetric source-drain silicene-based photodetectors

Photodetectors based on Armchair-Silicene-Nanoribbons (ASiNR) with asymmetric source (Ir-doped silicene) and drain (Cu-, Ag-, or Au-doped silicene) contacts have been simulated employing tight-binding approximation coupling to Non-Equilibrium Green’s Function (NEGF) approach. Monochromatic 1 kW cm−2 illumination in the range of 0.1–10 eV has been used for the simulation of the photocurrent, photoresponsivity, quantum efficiency, and detectivity. It is shown that the highest peak in the photocurrent spectrum occurs at the 273 nm incident wavelength for all devices, and the Ir-Cu device has presented enhanced photodetector characteristics than Ir-Ag and Ir-Au devices. It is also found that only transitions between two subbands with identical indexes are allowed. Moreover, the first peak in the photocurrent spectrum is related to the main band gap of ASiNR. Additionally, the simulated dark and total currents versus source-drain voltage reveal that photocurrent caused a negative shift in the total current proportional to incident light intensity.

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.

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.

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.

Diverse structural and electronic properties of carbon-substituted armchair silicene nanoribbons: A first-principles study

The structural and electronic properties of the armchair silicene nanoribbons (ASiNRs) under various C substitutions are investigated using the first-principles calculations. The C substitution-diversified structural and electronic properties are fully identified by the developed first-principles quantities, including the formation energies, phonon calculations, optimal structural parameters, orbital- and atom-projected density of states, and direction-projected spatial charge density distributions. The C substitutions at various adatom concentrations and distributions form the typical C substitution configurations of the single C, ortho-2C, meta-2C, para-2C, and 100% C, whereas the lower buckling height is found at the higher concentrations that become the flat 1D structure at 100% C substitution. The reshaped bandgaps are larger under shorter Si–C bond lengths. The largest opened bandgap of 2.37 eV is found at the highest adatom concentration of the 100% C configuration. The C substitutions generate the quasi σ bonds of the Si-(3s, 3p x , and 3p y ) and C-(2s, 2p x , and 2p y ) orbitals and the quasi π bonds of the Si-3p z and C-2p z orbitals, in which the quasi π orbitals create the long-range quasi π bands that determine the reshaped bandgaps. The quasi σ and π orbitals are hybridized at the middle valence energies that only separate at the deeper valence energies. The weak separation of the σ and π orbitals is responsible for the hybridization mechanism of the mixed sp 2 /sp 3 quasi in the C-substituted systems. The diverse electronic properties of the C-substituted ASiNRs will be very compatible with electronic and optoelectronic applications.

Thermoelectric performance of biased silicene nanoribbon in the presence of magnetic field

In this study with the tight binding model, we investigated the electronic and thermal properties of biased Armchair Silicene nanoribbon (AN-SiNR) in the presence of the perpendicular magnetic field. The band gap of AN-SiNRs decreases and increases with applying the vertical magnetic field and bias voltage, respectively. In the presence of magnetic field the DOS spectrum shows significant modifications such as splitting the DOS peak and changing the number of DOS peaks. The thermal properties of unbiased A16-SiNR in absence of external fields is negligible in low temperature and increases rapidly with temperature because the thermal energy increases with T. The bias voltage and magnetic field have opposite effects on the electronic and thermal properties of SiNRs. The increasing rate of thermal properties in terms of temperature decreases (increases) with bias voltage U (magnetic field Π) and the stronger U (Π) has smaller (larger) thermal properties due to increasing (decreasing) the band gap. The Lorenz coefficient has peak for each AN-SiNRs and it decreases by increasing the magnetic field and their peak positions move to lower temperature range. By comparing the thermal properties of A16-SiNR and A19-SiNR, we found that A19-SiNR has higher thermal properties because it has a smaller band gap in the present magnetic field and bias voltage and its charge carriers can be excited to conduction bands by lower thermal energy.

The spectral detectivity analysis of intrinsic, n-type and p-type A-SiNRs IR-photodetectors

In the present paper, the results of the performance of armchair silicene nanoribbons (A-SiNR) based Infrared (IR) photodetector using density functional theory (DFT) method are presented. A-SiNRs in different widths of group NA = 3 m in pure state and in the state applied by aluminum (Al) and phosphorus (P) atoms in optimize position as impurities have been studied. The results show that with increasing width and increasing temperature in the presence of impurity atoms, the spectral responsivity increases but the specific detectivity (D*) decreases due to increasing dark current. The maximum specific detectivity for the group NA = 3 m is observed in pure state, which the maximum specific detectivity value is related to the width NA = 6 and is equal to 3.7 × 1010 (cmHz1/2/W). The maximum spectral responsivity is observed in the width NA = 12 and the state in which the impurity Al atoms are applied, that is equal to 0.045 A/W.

Structural and electronic properties of silver-adsorbed silicene nanoribbons: A first-principles study

The geometrical and electrical features of Ag adsorption armchair silicene nanoribbons structure have been investigated using first-principles calculations. The findings reveal that the bandgap of doped Ag has changed, as it does for chemical adsorption on the surface of ASiNRs; this material became metallic at the valance band contact fermi level, with a mean bandgap of 0 eV. Furthermore, the survey to discover the best height 6.39 of Ag and 2.26 bond length Si-Si and Si-Si-Si bond angle 115015’ with structural stability near to the pristine situation has shown promising results for developing novel spintronic and optoelectronic materials in the future.

First-Principles Investigations of Al/P Co-doping Effect on Disconnected Armchair Silicene Nanoribbon for Switching Device Applications

First-Principles Investigations of Al/P Co-doping Effect on Disconnected Armchair Silicene Nanoribbon for Switching Device Applications

The effects of Co/Ni-vacancy complex defects on the electronic and transport properties of armchair silicene nanoribbon

The effects of Co/Ni-vacancy complex defects on the electronic and transport properties of armchair silicene nanoribbon

Applying first principles to study the structural, electronic, and magnetic properties of Pr adsorbed ASiNRs

Applying first-principles calculations, the investigation of the geometrical and electronic properties of Pr adsorption armchair silicene nanoribbons structure has been established. The results show that the bandgap doped Pr has been changed, which is the case for chemical adsorption on the surface of ASiNRs; this material became metallic with the peak of valance band contact fermi level. Moreover, the survey to find the optimal height 1.82 Å of Pr and 2.24 Å bond length Si-Si, and Si-Si-Si bond angle 108005’, energy adsorption is -7.65 eV, buckling is 0.43 Å with structure stability close to the pristine case, has brought good results for actively creating newly applied materials for the spintronic and optoelectronics field in the future.