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Borophenes have sparked considerable interest owing to their fascinating physical characteristics and diverse polymorphism. However, borophene nanoribbons (BNRs) with widths less than 2 nm have not been achieved. Herein, we report the experimental realization of supernarrow BNRs. Combining scanning tunneling microscopy imaging with density functional theory modeling and ab initio molecular dynamics simulations, we demonstrate that, under the applied growth conditions, boron atoms can penetrate the outermost layer of Au(111) and form BNRs composed of a pair of zigzag (2,2) boron rows. The BNRs have a width self‐contained to ∼1 nm and dipoles at the edges to keep them separated. They are embedded in the outermost Au layer and shielded on top by the evacuated Au atoms, free of the need for post‐passivation. Scanning tunneling spectroscopy reveals distinct edge states, primarily attributed to the localized spin at the BNRs' zigzag edges. This work adds a new member to the boron material family and introduces a new physical feature to borophenes. [ABSTRACT FROM AUTHOR]

Binary antimonene-phosphorene, a novel 2D semiconductor material, shows potential applications in gas sensing due to its favorable properties. In this work, the sensing properties of binary antimonene-phosphorene nanoribbons by varying the phosphorus mole fraction for the adsorption of NO, CO, NO2, CO2, SO2, SO3, H2S, NH3, O2, and N2 gas molecules are theoretically investigated with first-principles method based on the density function theory. The adsorption distance, adsorption energy, charge transfer, work function, and recovery time of gas molecules adsorbed on the different substrates of phosphorus mole fraction are calculated and compared to evaluate the sensing performance of these structures. The results demonstrate that all the examined gas molecules form stable physisorption with binary nanoribbons (except O2 molecule). Through the analysis of adsorption energy and charge transfer, it can be seen that binary nanoribbons with mole fractions of 25 and 75% have higher selectivity and sensitivity to gas molecules. For example, the charge transfer results show that there is more charge transfer from SO3 (0.456 e) and O2 (0.4 e) gas molecules to 25 and 75% phosphorus substrates than other substrates of mole fraction, respectively. Moreover, for a better comparison, the I–V characteristics of different phosphorus mole fraction are calculated for SO3 and O2 gases. The calculated current–voltage curves confirm the charge transfer results. As a result, our theoretical studies show that binary nanoribbons with some mole fractions can offer promising platform for gas sensing applications. [ABSTRACT FROM AUTHOR]

Although the transport of topological edge states may be insensitive to impurities, impurities may induce the interedge scattering and backscattering in topological nanoribbons due to the finite size effect. It may be interesting to compare the transport of topological edge states with that of trivial edge states in nanoribbons. Here, the quantum transport of edge states in the Sn-doped SbH nanoribbons using the density functional theory combined with nonequilibrium Green's function method is studied. Both topological and trivial edge states can be found in the zigzag SbH nanoribbons. The impurity generates a higher barrier near the doping position and leads to the scattering of the states. From calculations, the transmission of topological edge states can be smaller than that of trivial edge states due to the antiresonance behavior. Compared with topological edge states, the transport of trivial edge states is more sensitive to the impurity position. Besides, the edge impurity is more likely to induce scattering for both topological and trivial edge states than the central impurity in narrow SbH nanoribbons, since the transport channels are limited to the edges. This study may be helpful for understanding the transport of edge states in nanoribbons. [ABSTRACT FROM AUTHOR]

Based on density functional theory (DFT) and nonequilibrium Green's function (NEGF) framework, to study the monolayer (ML) blue phosphorene (BlueP) doped with C along zigzag direction, such as the structural stability, and electronic and transport properties. Interestingly, we found that doping engineering strategies can effectively transform monolayer ML ZBlueP doped with C into a spintronic nanodevice with a few unique transport properties. Firstly, our model showed a magnificently giant magnetoresistance (GMR) up to 10 $ ^4 $ 4 under low bias. Secondly, a rectifier with a large rectification ratio (RR) of 10 $ ^5 $ 5 was observed. Lastly, negative differential resistance with a peak-to-valley current ratio (PVCR) of 10 $ ^4 $ 4 was observed. Our research shows a promising route towards the development of high-performance ML ZBlueP spintronics technology by doping with C atom. Our results indicate that our models have immense potential for application in nanoscale spintronic devices. [ABSTRACT FROM AUTHOR]

This study's methodology employs the pristine Armchair Boron Nitride Nanoribbons (ABNNR) and Armchair Boron Nitride Nanoribbons Stone–Wales (ABNNR-SW) defects as carriers for the fluorouracil (FU), Nitrosourea (NU), and Thiotepa (TP) anticancer medicines. Utilizing density functional theory (DFT), the electrical properties of the interaction of FU, NU, and TP anticancer drugs with ABNNR and ABNNR-SW defects were studied. Our results show that ABNNR exhibits isolator behavior with a 6.155 eV energy gap, while the ABNNR-SW defect exhibits semiconductor behavior with a 3.862 eV energy gap. In addition, the energy gap was significantly reduced after the interaction of medicinal molecules with ABNNR and the ABNNR-SW defect substrate. The non-covalent interactions between the ABNNR and ABNNR-SW defects and anticancer medicines, which are important to the delivery process, were investigated in depth. The adsorption energies of the NU and TP drug molecules on the ABNNR-SW defect are much greater than those of the other complex structures with the Eads, which are − 30.667 and − 30.473 eV, respectively. This is a consequence of the Stone-Wales impact on the ABNNR structure, according to the results. In terms of specific drug delivery and biomedicine, the recovery period value indicates that ABNNR-SW is more suitable as a carrier for the NU and TP drugs, respectively. [ABSTRACT FROM AUTHOR]

The priority of research efforts over the past two decades has been focused on the effective detection of harmful gases and the development of small, efficient, and reliable nanodimensional sensors. The adsorption of carbon monoxide (CO) gas molecules on zigzag gallium phosphide nanoribbons (zGaPNRs) has been studied using first-principle calculations within the context of Density Functional Theory (DFT). Here, we have evaluated the potential of single-atom thick zGaPNRs in different configurations of nanoribbons for the detection of CO. Many possible configurations of studying the CO molecule adsorption on zGaPNRs have been explored. It is established that the interaction of CO molecules has an impact on the electrical and transport properties of zGaPNRs. The H-GaP-H is the most stable structure with the binding energy (Eb) of −5.70eV. The stability is compromised with CO adsorption with CO-GaP-CO being the least stable structure. Pristine structure is semiconducting with the energy band gap (EG) of −3.95eV. The computed sensitivity (S) values are found to be highest for Co-GaPNRs with the S value of 1.77×1018 and the least sensitive structure is H-GaP-CO with the computed S as 3.84×1017. Additionally, it is noted that CO molecules always establish a stable chemical bond with the nanoribbon edges through the C-side. The unique behavior is revealed by the transport characteristics, which demonstrates that when CO adsorption occurs near the Ga edge, the current magnitude is noticeably greater. Our research demonstrates the potential of specific CO adsorption and detection for the development of nanosensors. [ABSTRACT FROM AUTHOR]

First-principles calculations, using density functional theory, have been studied to investigate the sensing of NO2, NO, N2, CO2, CO, O2, NH3 and SO2 gases on bare and Fe-doped antimonene armchair nanoribbons (Fe-doped ASbNRs). The sensing behaviors of these gases on bare and Fe-doped ASbNRs have been analyzed in terms of band structure, the density of states, adsorption energy, charge transfer, magnetic moments and I–V characteristics. We showed that doping the magnetic Fe atom increases the sensing ability of antimonene nanoribbon where the gas molecules are chemisorption on Fe-doped ASbNR. This chemisorption induces dramatic change in the adsorption energy and electronic structures, and injects magnetic moments into the nanoribbon system. The NO molecule depicts the tightest binding in the Fe-doped ASbNRs. Charge transfer analysis of adsorbates demonstrates that all gas molecules, except NO, NH3 and CO are electron donors to nanoribbon. Transport properties of Fe-doped ASbNRs transistor, display desirable I–V characteristics and spin filter efficiency for the NO2, N2, and NH3 gases. These two-dimensional systems may possess the potential in the promising application of gas sensing. [ABSTRACT FROM AUTHOR]

Edge magnetism in zigzag nanoribbons of monolayer MoS 2 has been investigated with both density functional theory and a tight-binding plus Hubbard (TB+U) Hamiltonian. Both methods revealed that one band crossing the Fermi level is more strongly influenced by spin polarization than any other bands. This band originates from states localized on the sulfur edge of the nanoribbon. Its dispersion closely resembles that of the energy branch obtained in a linear chain of atoms with first-neighbor interaction. By exploiting this resemblance, a toy model has been designed to study the energetics of different spin configurations of the nanoribbon edge. [ABSTRACT FROM AUTHOR]

Molecular switches based on functionalized graphene nanoribbons (GNRs) are of great interest in the development of nanoelectronics. In experiment, it was found that a significant difference in the conductance of an anthraquinone derivative can be achieved by altering the pH value of the environment. Building on this, in this work we investigate the underlying mechanism behind this effect and propose a general design principle for a pH based GNR-based switch. The electronic structure of the investigated systems is calculated using density functional theory and the transport properties at the quasi-stationary limit are described using nonequilibrium Green's function and the Landauer formalism. This approach enables the examination of the local and the global transport through the system. The electrons are shown to flow along the edges of the GNRs. The central carbonyl groups allow for tunable transport through control of the oxidation state via the pH environment. Finally, we also test different types of GNRs (zigzag vs. armchair) to determine which platform provides the best transport switchability. [ABSTRACT FROM AUTHOR]

The aim is to tune the stability, as well as electronic and magnetic characteristics of zigzag α‐borophene nanoribbons (ZαBNRs) based on density functional theory. For this reason, the bare ZαBNR and its passivated edges by a single nitrogen atom (N‐ZαBNR) and also Mn‐ and Cr‐doped N‐ZαBNR is investigated. The results indicate that the nanoribbon becomes more stable by passivating the edges of the structure. Furthermore, the calculated electronic structures show that the Cr atom can remove the band gap of N‐ZαBNRs and turn it into metal. Besides, it can create magnetic properties in this structure. The Cr‐ and Mn‐doped N‐ZαBNR turn it into magnetic metal and diluted magnetic semiconductors, respectively. The results reveal a high Curie temperature of more than 700K for Cr‐ and Mn‐doped N‐ZαBNRs, indicating maybe good room‐temperature ferromagnetic material for spintronic applications in the future. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the potential of zigzag phosphorene antidot nanoribbons (ZPANRs) for biosensing applications. ZPANRs were created from the optimized structures of phosphorene nanoribbons by using a density functional theory tool. Utilizing the generalized gradient approximation half method for improving the accuracy of calculations, we have studied the electronic and sensing behavior of ZPANRs based devices wherein nucleobases were inserted into the device. We have compared the device performance of ZPANRs with and without nucleobases and found that using ZPANRs devices, we are able to identify different nucleobases with considerable sensitivity. In a quantitative manner, a max sensitivity of 45 % is achieved while identifying adenine nucleobase using the ZPANRs based devices. From these simulation results, it is predicted that the ZPANR based two-terminal device can work as a possible biosensor. [ABSTRACT FROM AUTHOR]

Based on an empirical approach, we present a relation for the bandgaps of armchair graphene nanoribbons (aGNRs) as a function of their widths and number of armchair chains. Experimental bandgaps of a number of atomically well-defined aGNRs are studied here. It is found that experimentally reported bandgaps are underestimated or overestimated by existing theoretical models. Experimental data reveal that the bandgaps of N = 3p and N = 3p + 1 families of aGNR are directly related to the width and number of armchair chains. An empirical model for calculating the bandgaps of aGNRs is devised based on theoretical and experimental observations. Calculated bandgaps offer significant corrections for armchair aGNRs compared with previous tight-binding and density functional theory studies, and the amount of correction is represented by a semi-empirical correction term. The proposed relation indicates that not only the ribbon width but also the number of armchair chains plays a crucial role in determining the values and scaling rule for the bandgaps. Compared with previous models, our estimated bandgaps from the proposed empirical model can track qualitative and quantitative patterns of the experimental bandgaps very precisely, thus helping predict the bandgap of an aGNR for potential electronic and optoelectronic applications. The proposed empirical relation also gives insight into the correlation between the physical structure and electronic properties of a GNR. Furthermore, this model can be taken as a guide for devising a similar empirical model for calculating the bandgaps of other types of GNRs. [ABSTRACT FROM AUTHOR]

In this study, armchair graphene nanoribbons (AGNRs) and AGNRs Stone–Wales defects-based delivery nanomaterials were developed via QuantumATK and used to deliver four anticancer drugs (Hydroxyurea (HU), Thiotepa (TP), Nitrosourea (NU), and Fluorouracil (FU)). Using density functional theory (DFT), the electrical and optical characteristics of the interaction of HU, TP, NU, and FU molecules on AGNRs and AGNRs-SW defects were investigated. The results indicate that AGNRs and AGNRs-SW are more stable and less reactive after interaction with HU, TP, NU, and FU anticancer drugs, as a consequence of the rise in total energy values. The highest Eads values for the HU/AGNRs-SW, TP/AGNRs-SW, NU/AGNRs-SW, and FU/AGNGs-SW structures are −7.534, −5.917, −8.972, and −6.027 eV, respectively. On the basis of these values, it has been determined that AGNRs-SW has a greater attraction for HU, TP, NU, and FU molecule adsorption than other structures. [ABSTRACT FROM AUTHOR]

The edge elasticity and its effect on flexoelectric response of the Janus MoSSe nanoribbons are systematically explored by means of density functional theory based first-principles calculations. We report edge stresses, edge elastic moduli, and structural deformations of the Janus MoSSe nanoribbons with various widths. It is shown that both armchair and zigzag terminated edges of the MoSSe nanoribbons are essentially subjected to tension, due to the existence of the edge stresses. The magnitude of average zigzag edge stresses is much larger than that of the average armchair ones. Furthermore, our results show that both misfit strain induced by asymmetric chalcogen atomic layers, and the edge stresses cause the spontaneous bending deformation of such Janus nanoribbons. More importantly, flexoelectronic properties of semiconducting armchair MoSSe nanoribbons are carefully evaluated and compared with those of armchair MoS 2 and MoSTe nanoribbons. In particular, it is found that the out-of-plane flexoelectronic coefficients strongly depend on their widths. Additionally, the flexoelectric response resulting from spontaneous bending is weaker than that from the opposite one. The implicit mechanisms on deformations and flexoelectronic properties of such Janus nanoribbons have been carefully explored. The results in this work provide useful insights into their potential applications in nanoscale electromechanical systems. [ABSTRACT FROM AUTHOR]

The dimensions of nanoribbons have a significant impact on their material properties. In the fields of optoelectronics and spintronics, one-dimensional nanoribbons exhibit distinct advantages due to their low-dimensional and quantum restrictions. Novel structures can be formed by combining silicon and carbon at different stoichiometric ratios. Using density functional theory, we thoroughly explored the electronic structure properties of two kinds of silicon–carbon nanoribbons (penta-SiC2 and g-SiC3 nanoribbons) with different widths and edge conditions. Our study reveals that the electronic properties of penta-SiC2 and g-SiC3 nanoribbons are closely related to their width and orientation. Specifically, one type of penta-SiC2 nanoribbons exhibits antiferromagnetic semiconductor characteristics, two types of penta-SiC2 nanoribbons have moderate band gaps, and the band gap of armchair g-SiC3 nanoribbons oscillates in three dimensions with the width of the nanoribbon. Notably, zigzag g-SiC3 nanoribbons exhibit excellent conductivity, high theoretical capacity (1421 mA h g−1), moderate open circuit voltage (0.27 V), and low diffusion barriers (0.09 eV), making them a promising candidate for high storage capacity electrode material in lithium-ion batteries. Our analysis provides a theoretical basis for exploring the potential of these nanoribbons in electronic and optoelectronic devices as well as high-performance batteries. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron oxygen reduction reaction (2 e− ORR) to produce hydrogen peroxide (H2O2) is a promising alternative to the energetically intensive anthraquinone process. However, there remain challenges in designing 2 e− ORR catalysts that meet the application criteria. Here, we successfully adopt a microwave‐assisted mechanochemical‐thermal approach to synthesize hexagonal phase SnO2 (h‐SnO2) nanoribbons with largely exposed edge structures. In 0.1 M Na2SO4 electrolyte, the h‐SnO2 catalysts achieve the excellent H2O2 selectivity of 99.99 %. Moreover, when employed as the catalyst in flow cell devices, they exhibit a high yield of 3885.26 mmol g−1 h−1. The enhanced catalytic performance is attributed to the special crystal structure and morphology, resulting in abundantly exposed edge active sites to convert O2 to H2O2, which is confirmed by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron oxygen reduction reaction (2 e− ORR) to produce hydrogen peroxide (H2O2) is a promising alternative to the energetically intensive anthraquinone process. However, there remain challenges in designing 2 e− ORR catalysts that meet the application criteria. Here, we successfully adopt a microwave‐assisted mechanochemical‐thermal approach to synthesize hexagonal phase SnO2 (h‐SnO2) nanoribbons with largely exposed edge structures. In 0.1 M Na2SO4 electrolyte, the h‐SnO2 catalysts achieve the excellent H2O2 selectivity of 99.99 %. Moreover, when employed as the catalyst in flow cell devices, they exhibit a high yield of 3885.26 mmol g−1 h−1. The enhanced catalytic performance is attributed to the special crystal structure and morphology, resulting in abundantly exposed edge active sites to convert O2 to H2O2, which is confirmed by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide has attracted significant research attention as a nanocatalyst for hydrogen evolution reaction. In this study, the effects of nanoribbons on the catalytic performance of molybdenum disulfide in the hydrogen evolution reaction are evaluated via the density functional theory. Co is considered to be an effective promoter of Mo-based catalysts. Thus, the promotion of the Mo-edge was studied here in a number of Co-substituted surface models. The results show that the electronic structure of the molybdenum disulfide nanoribbons changed after doping with Co atoms; this change significantly reduced the Gibbs free energy of the hydrogen evolution reaction and improved the reaction activity. In addition, the effects of stress regulation on the catalyst were analyzed. Tensile and compressive stresses were applied to the catalyst in the x direction. The results indicate that the distance between atoms changed owing to the effects of stress, and changes were also observed in the electronic properties. The insights obtained from this study will be helpful to further improve the activity of catalysts. [ABSTRACT FROM AUTHOR]

The modifications of the electronic properties on carbon-doped boron nitride nanoribbons (BNNRs) as a response to the adsorption of different nitro species were investigated in the framework of the density functional theory within the generalized gradient approximation. Calculations were performed using the SIESTA code. We found that the main response involved tuning the original magnetic behavior to a non-magnetic system when the molecule was chemisorbed on the carbon-doped BNNR. It was also revealed that some species could be dissociated through the adsorption process. Furthermore, the nitro species preferred to interact over nanosurfaces where dopants substituted the B sublattice of the carbon-doped BNNRs. Most importantly, the switch on the magnetic behavior offers the opportunity to apply these systems to fit novel technological applications. [ABSTRACT FROM AUTHOR]

Germanium selenide (GeSe) nanoribbons as quasi-one-dimensional materials are expected to host fascinating tunable electronic properties due to the edge state and quantum confinement effect. Herein, the effect on the electronic structures and transport properties of zigzag GeSe nanoribbon (ZGeSeNR) of different functional passivation groups is systematically studied using a combination of density functional theory and the non-equilibrium Green's function. The N-, P-, and S-passivated ZGeSeNRs are metallic, while the F-, Cl-, OH-, and H-passivated ones exhibit semiconductor properties. The rectification behavior is found in lateral ZGeSeNR heterojunctions composed of a metal–semiconductor contact, and the rectification performance can be modulated by changing the edge passivation group, the ribbon width, and the length of the scattering region. Especially, the highest rectification ratio (RR) reaches 9.2 × 106 in the S–H–ZGeSeNR heterojunctions, in which the left and right half-edge atoms are passivated by the S and H groups, respectively. These results are useful for the design of nanoscale rectifiers based on ZGeSeNRs. [ABSTRACT FROM AUTHOR]

In this work, we examined geometry, electronic structure, and edged termination effect of boron‐nitride nanoribbons (BNNRs) by employing localized Gaussian‐type orbital, periodic‐boundary condition, density functional theory (LGTO‐PBC‐DFT) calculations. Armchair (ABNNR) and zigzag (ZBNNR)‐type BNNRs are obtained and then bond lengths variation in two types of BNNRs are analyzed. We find that the B‐N bond length variation of ZBNNR is less diverse than that of ABNNR, and decreases with an increase in the ribbon width, monotonically. For those in ABNNR, it appears as an oscillatory convergence as a function of the ribbon width. The energy gap of edged termination ABNNR and ZBNNRs are also calculated using OH and SH as electron donating groups and CN‐, and Cl‐ as electron‐withdrawing groups. The introduction of SH‐ and Cl‐terminator significantly reduce the energy gap to the semiconducting region for ZBNNR, but for ABNNR. These calculated results may be exploited for nano‐electronic applications. To examine the surface behavior of the BNNRs, we also calculated their Raman shifts with the edge termination effects. [ABSTRACT FROM AUTHOR]

By performing extensive density functional theory calculations combined with non‐equilibrium Green's function technique, we predict the rhombic porous carbon nitride nanoribbon (rPCNNR) and the vertical rPCNNR junction exhibiting high thermoelectric figure of merit (ZT) values of 0.57 and 2.1 at room temperature respectively. Theoretical results reveal that the ZT value of rPCNNR is significantly larger than that of armchair graphene nanoribbon with the almost same width (~0.035) due to the large Seebeck coefficients and the significantly decreased thermal conductance of rPCNNR, where the phonon states are blocked by the built‐in porous structure and rhombic edge in rPCNNR. The ZT value is further enhanced to be 2.1 in the vertical rPCNNR junction, which is achieved by the synergy effect between the dramatically suppressed thermal conductance in in‐plane direction due to the weak van der Waals interaction between two rPCNNRs, the almost unchanged Seebeck coefficients, and the good electron conductivity provided by the strong overlapping of delocalized VB‐ and CB‐derived states in the scattering region. These presented findings highlight rPCNNR as a promising candidate in building flexible devices with high thermoelectric performance. [ABSTRACT FROM AUTHOR]

In the last decade, surface-assisted reactions involving well-defined molecular precursors have led to the controlled assembly of several clean-edged and defect-free graphene nanoribbons. The recent realization of a bisanthene-like quantum dot with pairs of pentagon–heptagon, or Stone–Wales (SW), defects has been successfully achieved. Based on the similarity between the pristine and SW-defective bisanthene blocks, we propose a set of systems based on the concatenation of SW-bisanthene motifs and study their electronic properties using density functional theory. We demonstrate that nanoribbons with SW-defects preserve the semiconducting character of their pristine counterparts. Furthermore, noteworthy behaviors involving the frontier levels emerge, which affect carrier mobilities of both electrons and holes. We also investigate the electronic transport properties of nanojunctions composed by graphene nanoribbons with a localized distribution of SW-defects compatible with the geometry of the corresponding bisanthene-like blocks. Our simulations shown that the transmission spectrum is sensitive to the position and concentration of SW-defects. [Display omitted] [ABSTRACT FROM AUTHOR]

We propose a quasi-one-dimensional P-substituted tellurene nanoribbon (TeNR) (with sizes ranging from 7 to 5 Å) based on a β-Te monolayer configuration using the first principles of density functional theory (DFT) calculations. This system appears to have outstanding electronic and optical properties as revealed by its energy band structure, density of state (DOS), and optical spectrum. P-substituted TeNR has lower formation energy than that of pristine TeNR, indicating that it is more stable than the pristine TeNR. In the presence or absence of the spin–orbit coupling (SOC), P-substituted TeNRs were semiconductors and their direct bandgaps decrease with increasing bandwidth. The DOS and projected DOS are mainly derived from the contributions of the p orbital electrons of Te and P atoms. The dielectric functions of P-substituted TeNRs exhibited optical anisotropy. The absorption spectrum is selective for the incident light energy, and an absorption peaks in the visible and ultraviolet regions indicate that P-substituted n-TeNRs could not only harvest considerable visible light but also capture ultraviolet light, and the peaks also have a trend of red-shift. These findings on quasi-one-dimensional Te nanostructures effectively extend the realm of group VI elements. [ABSTRACT FROM AUTHOR]

The structural and electronic properties of group III-nitride nanoribbons have been systematically investigated using density functional theory calculations. We computed the edge stresses and edge moduli for III-nitride nanoribbons with a variety of widths and edge terminations, including bare, fully as well as partially hydrogen-passivated edges. In addition, fluorine-passivated zigzag-terminated nanoribbons were also investigated. Our results show that all edges of III-nitride nanoribbons are subjected to compressive stresses. The magnitude of edge stresses strongly depends on the edge terminations. Compressive stress states of nanoribbon edges result in drastically different edge distortions and edge elastic moduli, depending again on the edge configurations. Finally, the electronic band structures are calculated for all zigzag-terminated nanoribbons. We found only fully-passivated nanoribbons are semiconductors with indirect bandgaps. These results suggest that edge terminations significantly affect the edge elastic properties as well as the electronic properties of group III-nitride nanoribbons and their applications. [ABSTRACT FROM AUTHOR]

We present an atomistic model for predicting the distribution of doping electric charges in layered molybdenum disulfide (MoS2). This model mimics the charge around each ion as a net Gaussian-spatially distributed charge plus an induced dipole, and is able to predict the distribution of doping charges in layered MoS2 in a self-consistent scheme. The profiles of doping charges in monolayer MoS2 flakes computed by this charge-dipole model are in good agreement with those obtained by density-functional-theory calculations. Using this model, we quantitatively predict the charge enhancement in MoS2 monolayer nanoribbons, with which strong ionic charge-localization effects are shown. [ABSTRACT FROM AUTHOR]

A two-dimensional polyaniline sheet has been recently synthesized and found that it is a semiconductor with an indirect band gap. Polyaniline nanoribbons decomposed from the two-dimensional polyaniline sheet (C3N sheet) are investigated using a density functional theory. The existence of nitrogen atoms in the edge of the ribbons increases the stability and magnetization of the ribbons and make them different from graphene nanoribbons. Unsaturated nanoribbons are magnetic metals so that the armchair C3N nanoribbons are gap-less spin semiconductors in the antiferromagnetic state and half-metals in the ferromagnetic state. A transition from a metal to semiconductor is observed in the armchair C3N nanoribbons when the edge atoms are passivated by hydrogen. The band gap of the hydrogen saturated armchair C3N nanoribbons can be controlled using an external transverse electric field so that its magnitude is dependent on the direction of the electric field. Being a metal or semiconductor in hydrogen saturated zigzag C3N nanoribbons is strongly dependent on the edge atoms so that just ribbons having nitrogen atoms in both edges are semiconductor. An external electric field cannot induce any spin polarization in the zigzag nanoribbons, which is in contrast with what was observed in zigzag graphene nanoribbons. [ABSTRACT FROM AUTHOR]

Based on the density functional theory in combination with the nonequilibrium Green's function formalism, we study the structural, electronic, and transport properties of SS-pSiC2 NRs under a sequence of uniaxial strains in the range from 10% compression to 10% stretch. The pentagon network of SS-pSiC2 NRs is still maintained, but the bond length along the strained direction is largely changed under this strain. The electronic band structure and bandgap are strongly affected by the uniaxial compressive strain. The evolution of the bandgap vs the strain is linear. With a bias voltage of 2 V, the current of the 10% compressed sample increased 75 times, and the current of the 10% stretched sample increased 2.5 times compared to the one of the relaxed sample. The I–V characteristic of SS-pSiC2 NRs seems to be more sensitive to compressive strain than the stretch strain. Our calculations may indicate new applications of strain structures in electromechanical devices based on SS-pSiC2 NRs. [ABSTRACT FROM AUTHOR]

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 1015, 1012, and 108, respectively. The calculated GMR and spin-RR of the 1H-AlN-1H device are 107 and 102 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. [ABSTRACT FROM AUTHOR]

Resonant Raman spectra of armchair graphene nanoribbons (AGNRs) are computed using Density Functional Theory (DFT) and third-order perturbation theory. Results are benchmarked against available experimental data and compared to previously used theoretical approaches based on the Placzek approximation. Comparable agreement with experiments is found for both previously and presently used methods. In addition, a numerical analysis is carried out to provide a justification for the resonant modeling method based on the use of the frequency-dependent dielectric tensor in the Placzek approximation. This work also provides additional predictions and references for wide AGNRs that might be investigated with Raman scattering experiments in the future. [Display omitted] [ABSTRACT FROM AUTHOR]

• We comprehensively investigated the structural and magnetic properties of armchair Sb, P, and binary SbP nanoribbons. • Doping of these nanoribbons with 3d transition metal atoms (Ti, Cr, Mn, Fe, Co, and Ni) with various concentrations of dopant atoms have been analyzed. • It was found that the magnetic properties for single P and Sb nanoribbons do not depend on the substitution position of TM atoms. • The magnetization for substitution of Fe and Co atoms in the P position of the binary SbP nanoribbon will be greater than those of the Sb position. • The increasing of the number of impurity atoms in the nanoribbon leads to the magnetic moment increments, except for the nickel atom in the Sb position of the SbP nanoribbon, in which the nanoribbon prefers the ferrimagnetic state. Binary antimonene-phosphorene, a novel two-dimensional material with a medium band gap, high carrier mobility, and environmental stability, has attracted growing attention due to its wide applications in spintronics. Using density functional theory, we comprehensively investigate and compare the structural and magnetic properties of armchair Sb, P, and binary SbP nanoribbons doped with 3d transition metal atoms (Ti, Cr, Mn, Fe, Co, and Ni) with various concentrations of dopant atoms. We investigated magnetic properties, including magnetic moment, spin polarization, and spin density. It was found that the magnetic properties for single P and Sb nanoribbons do not depend on the substitution position of TM atoms. In contrast, for binary SbP nanoribbons, the substitution of TM atoms in P or Sb positions leads to different behaviors. For example, the magnetization for substitution of Fe and Co atoms in the P position of the binary SbP nanoribbon will be greater than those of the Sb position, but for other impurity atoms, the magnetization of the binary SbP nanoribbon does not strongly depend on the substitution position. The results show that with increasing the number of impurity atoms in the nanoribbon, the magnetic moment increases, except for the nickel atom in the Sb position of the SbP nanoribbon, in which the nanoribbon prefers the ferrimagnetic state. Also, the spin density results show that the magnetism of the doped systems is mainly attributed to the dopant atoms, and the neighboring atoms have a negligible contribution. The findings of antimonene-phosphorene nanoribbons doped with TM atoms may have potential applications in spintronic nanodevices. [ABSTRACT FROM AUTHOR]

Nanoribbons exhibit peculiar electron confinements which could be further tuned via controlled edge passivations. In this direction, we used density functional theory (DFT) to reveal the structural, electronic and transport characteristics of zigzag BP nanoribbons (ZBPNR) having various possible edge passivations with H and/or F. We categorized the considered nanoribbons in different groups depending upon type of passivations. It is revealed that sp 2 and sp 3 passivations of ZBPNR with H/F are always energetically feasible with comparable binding energies. The covalent (ionic) bonding has been confirmed for B-P (B/P-F) on the basis of charge density and electron localization analysis. The magnitude of band gap is reciprocal of the ribbon width and a semiconductor to metallic transition is also witnessed in selected configurations. Amongst semiconductor nanoribbons, the obtained band gap varies from 1.41 eV (direct) to 0.11 eV (indirect). Furthermore, the electron transport analysis reveals p–n junction like characteristics whereas the negative differential resistance phenomenon has been confirmed for selective nanoribbons. These findings can play a pivotal role in designing beyond Si semiconductor nano-electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• The spin-dependent electronic transport properties of zigzag phosphorene nanoribbons (ZPNRs);. • The electronic transport through the ZPNRs shows apparent spin polarization;. • The spin polarization is tightly dependent on the absorbing manners;. • Negative differential resistance characteristic can be observed on current-voltage curves. Based on density functional theory (DFT) and non-equilibrium Green's function (NEGF) method, we have investigated spin-dependent electronic transport properties of zigzag phosphorene nanoribbons (ZPNRs) coupled with chromium triiodide (CrI 3) molecules. Three different adsorption models have been considered: CrI 3 molecule is placed on ZPNR surface (C-type), and CrI 3 molecule is lateral adsorbed on the edge of ZPNR with its molecule panel vertical (V-type) or parallel (P-type). We discovered that ZPNR's electrical transport clearly displays spin polarization, owing to the coupling between ZPNR and CrI 3 molecules. And spin-polarization is tightly dependent on the absorbing manners. Moreover, the negative differential resistance (NDR) characteristics can be observed from current-voltage curves and modulated by absorbing molecules. Furthermore, we also discovered that CrI 3 is vertically adsorbed on the surface of the ZPNRs has a better spin-polarization efficiency than the other two cases. [ABSTRACT FROM AUTHOR]

The atomic and electronic structures of armchair and zigzag ZrSe2 nanoribbons have been investigated systematically. Both the armchair and zigzag ZrSe2 nanoribbons are nonmagnetic semiconductors, while their bandgaps show quite different behaviors depending on the ribbon width. We find that all the zigzag ribbons possess direct energy gaps, which smoothly decline with the increasing ribbon width. On the other hand, energy gaps for the armchair ribbons change from direct gaps to indirect ones as the ribbon width increases and exhibit a width-dependent oscillation behavior. Moreover, the semiconducting behaviors and the bandgap types are robust, and they remain unchanged in bilayer and multilayer thin films with inter-layer interactions. These findings indicate that ZrSe2 nanoribbons are promising candidate materials for applications in nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Using density functional theory method, the linear optical absorption spectra and nonlinear optical susceptibilities of hydrogen passivated armchair and zigzag Phosphorous Nanoribbons (aPNR and zPNR) as well as α-phase phosphorous monolayer were calculated. It was observed that the crystallographic direction has a strong effect on the band edge absorption which in turn leads to optical anisotropy as well as a red shift of the absorption spectra by increasing the width. The calculated absorption values are in the order of 105 cm−1 and are very close to the experimentally measured ones. It was also observed that the 2nd order nonlinear optical susceptibility, χ(2), in the nanoribbons is enhanced by two orders of magnitude. This effect is caused by breaking the centro-symmetric structure of monolayer phosphorene as a result of hydrogen surface termination. The calculated 3rd order susceptibilities, χ(3), are in the order of ≈10−13 esu (≈10−21 m2/V2) which are in close agreement with experimentally reported values as well as those computed based on the relativistic picture of electron. The closeness of our results to experimental values strongly supports the reliability of our method in calculating the nonlinear optical susceptibilities of phosphorene and other nanostructures in general. The enhanced 2nd order optical nonlinearity in phosphorene promises a better second harmonic and frequency difference (THz) generation. [ABSTRACT FROM AUTHOR]

Graphene nanoribbons (GNRs) can be mainly classified into armchair graphene nanoribbons (aGNRs) and zigzag graphene nanoribbons (zGNRs) by different edge chiral directions. In this work, by introducing Stone-Wales defects on the edges of the V-shaped aGNRs, we propose a kind of armchair/zigzag edge hybridized GNRs (a/zHGNRs) and using the density functional theory and the nonequilibrium Green's function method, the band structures and electronic transport properties of the a/zHGNRs have been calculated. Our results show that an indirect bandgap appears in the band structures of the a/zHGNRs, which is very different from the direct bandgap of aGNRs and gapless of zGNRs. We also find that the valance band is mainly derived from the armchair partial atoms on the hybridized edge, while the conduction band comes mainly from the zigzag partial atoms of the hybridized edge. Meanwhile, the bandgap also oscillates with a period of three when the ribbon width increases. In addition, our quantum transport calculations show that there is a remarkable transition between the semiconductor and the metal with different ribbon widths in the a/zHGNRs devices, and the corresponding physical analysis is given. [ABSTRACT FROM AUTHOR]

Similar to graphene nanoribbons, boron nitride nanoribbons are prone to twist intrinsically. Hence, investigating the effect of local torsion on the electromechanical properties of boron nitride nanoribbons (9-cells) is of great importance. By using the density functional theory in combination with the non-equilibrium Green's function method, the effect of local torsion on the structural evolution and electrical transport of armchair boron nitride nanoribbons is investigated here. In addition, the electrical transport, current–voltage and Local density of state (LDOS) are studied. It is shown that local twist can change the transport properties of the boron nitride nanoribbons significantly. The current at a given bias can switch on/off or change many times with twist angle, which is related to twist-induced changes in electronic structures of boron nitride nanoribbons. The results of the current work can provide a valuable guideline for design and implementation of boron nitride nanoribbons in nanoelectromechanical systems and devices. [ABSTRACT FROM AUTHOR]

Using the density functional theory, we calculate electronic states of various nanoribbons and nanodiscs formed from selected two-dimensional materials, such as graphene, silicene, and hexagonal boron nitride. The main objective of the analysis is a search for zero-energy states in such systems, which is an important issue as their presence indicates certain topological properties associated with chirality. The analysis is also supported by calculating transport properties. [ABSTRACT FROM AUTHOR]

2D semiconducting transition metal dichalcogenides (TMDs) have attracted interest for optoelectronics, catalysis, and energy applications. Control over TMD electronic and optical properties, which depend on dimensionality and are modified by nanostructuring and adsorbates, is important for the development and deployment of reliable nanoscale devices for such applications. Density functional theory calculation results for the atomic structure, energetics, and electronic structure of the metal edges of 2D MX2 (M = Mo, W and X = S, Se) with several coverages of adsorbed hydrogen, oxygen, hydroxyl radicals, and water are presented. Using zigzag nanoribbon models, it is found that compared with the basal planes of MX2, edges are more active and exhibit a rich adsorbent behavior. In general, the thermodynamically stable M‐edges, with two X adatoms, weakly bind hydrogen, oxygen, and water and strongly bind hydroxyl. However, adsorption energies depend on the adsorbate type and coverage and may be tuned for the catalysis of important chemical reactions such as water splitting and hydrogen evolution. The electronic band structure calculations show that, besides bandgap energy modifications and gap states, the well‐established robust metallic character of the edge states is preserved, albeit Fermi‐level shifts that depend both on adsorbates and adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic effect of carbon edges and dopants towards ORR was predicted by DFT. • Well-designed N -GNRs contain both heteroatom-doping and abundant edge sites. • Best ORR property was obtained for N -GNRs compared to other control samples. • The synergistic effect was again demonstrated by experimental facts. Decoration with alien atoms and increasing the edge content are two valid ways to activate the oxygen reduction reaction (ORR) property of nanocarbons. To further enhance their intrinsic activity and explore the underlying ORR mechanism, graphene nanoribbons (GNRs) were selected as an ideal catalyst model. Theoretical simulations have predicted that with the synergistic effect between heteroatom-doping and edge sites, the ORR activity can be significantly improved. Inspired by this, N -GNRs were synthesized via the oxidative unzipping of CNTs followed by nitrogen incorporation with urea. Ample edges and nitrogen doping sites were detected by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. As a result, N -GNRs exhibited remarkably higher ORR properties in terms of onset and half-wave potentials, Tafel slopes, electron transfer number and methanol tolerance than either GNRs, the control sample without doping, or N -CNTs, the control sample without abundant edges, simply clarifying the significance of synergy between dopants and edges. Thus, this work provides a simple but efficient strategy to fabricate high-performance oxygen reduction catalysts. [ABSTRACT FROM AUTHOR]

Density functional theory calculations are performed to study the adsorption and migration behavior of a lithium (Li) atom on tetra‐penta‐hepta (TPH)‐graphene nanoribbon (GNR). The unit cell of the TPH‐GNR consists of three different polygons: tetragon, pentagon, and heptagon. The non‐hexagonal polygon sites strengthen the Li adsorption, and the tetragon site shows the strongest adsorption. The Li atom can migrate on the nanoribbon with a low energy barrier of 0.40 eV through pentagon and heptagon, but a high energy barrier of 0.89 eV through tetragon. [ABSTRACT FROM AUTHOR]

Using first‐principles density functional theory calculations, 1D armchair graphene nanoribbons (AGNRs) and graphene with an extended line defect (ELD) mimicking a grain boundary (GB) are investigated. Two AGNRs with n and m indices are laterally coupled, generating an ELD with alternated four‐ and eight‐membered carbon rings. Band structure, electronic density of states, wave functions, scanning tunneling microscope image, and quantum transport are analyzed. Unlike the conventional semiconducting behavior of AGNRs, the authors demonstrated that AGNRs with a 4‐8‐ELD exhibit a metallic behavior for n = m = 3p + 2 (p ≥ 0). They further demonstrate that graphene with 4‐8‐ELDs is metallic compared to the semi‐metallic behavior shown by the pristine graphene. Additionally, they investigate the effect of a single vacancy placed at the 4‐8‐ELDs on the electronic properties of AGNRs. The present investigation provides a theoretical basis to tailor graphene structures with possible applications in electronic devices. [ABSTRACT FROM AUTHOR]

To analyse the suitability of zigzag graphene nanoribbons (ZGNRs) as interconnects, the influence of halogen (F, Cl, Br, and I) passivation on ZGNRs has been analysed in terms of structural stability, electron transport, and thermal conductivity, as well as the performance parameters of the interconnects. The computation is performed using first-principle density functional theory with a non-equilibrium Green’s function approach, while the performance parameters of the interconnects such as delay and power delay product are computed using a HSPICE simulator tool. The formation energy analysis confirms the stability trend for halogen-passivated ZGNRs as F > Cl > Br > I. With moderate stability, the I- and Br-passivated ZGNRs have relatively better currentâ€"voltage characteristics in comparison to F and Cl. However, the Cl-passivated ZGNRs have relatively better interconnect parameters in comparison to other proposed halogenated systems (one edge and both edges), measured in terms of kinetic inductance and quantum capacitance. Another requirement of any good interconnect is less delay and less average power, which have also been computed and found to be relatively better in the case of Cl-passivated ZGNRs. Thus, among the halogen-passivated GNRs tested, those that are Cl-passivated defend their selection for interconnect applications well. [ABSTRACT FROM AUTHOR]

In this study, we investigate the spin-dependent electron transport properties of a zigzag silicene nanoribbon (ZSiNR) by using spin-polarized density functional theory and the non-equilibrium Green's function method. The results show that such a ZSiNR with an FM configuration exists the perfect dual spin filtering and dual spin diode effects when the bias voltage was applied. These phenomena still exist in ZSiNRs with different widths. As the ribbon width increases, the progressively smaller bias voltage is required to trigger a polarized current. Therefore, such a ZSiNR in FM configuration is a good candidate for spintronic devices. [ABSTRACT FROM AUTHOR]