Properties Of Boron Nitride Nanoribbons Research Articles

Electronic and optical properties of boron nitride nanoribbons exploiting DFT

We have used density functional theory and the SIESTA code to investigate the electronic bandgap and optical spectra of zigzag boron nitride nanoribbons n-ZBNNRs (n = 18, 22, 26, 30). The electronic structure of the simulated nanoribbons reveals that they are semiconductors with a bandgap of 4.87–4.95 eV. For energies greater than 5 eV, the real part of the dielectric function suggests that ZBNNRs are negative refractive index materials. n-ZBNNRs also have a lower static refractive index than armchair graphene nanoribbons. The fundamental reason is that the boron nitride nanoribbons have more localized electrons. The optical absorption of n-ZBNNRs (n = 18, 22, 26, 30) is anisotropic for the x, y, and z polarizations as well. Moreover, Eoptical gap18-BNNRs = 4.95 eV, Eoptical gap22-BNNRs = 4.94 eV, Eoptical gap26-BNNRs = 4.92 eV, and E optical gap30-BNNRs = 4.87 eV. The maximum optical extinction occurs at E ≈ 6–7 eV for the y polarization and E ≈ 5–6 eV for the z-direction. Besides, by around 6 eV for the y polarization (and 5 eV for the z polarization), σ is almost 1500 Ω−1 cm−1 (and 860–1500 Ω−1 cm−1). The imaginary part of the optical conductivity indicates that for the low energy range, n-ZBNNRs (n = 18, 22, 26, 30) supply the conditions of the transverse-electric mode existence. In addition, for $$E_{y} \, > \,6$$ eV and $$E_{x} \, > \,5$$ , n-ZBNNRs (n = 18, 22, 26, 30) support the transverse-magnetic plasmons.

On the effect of local torsion on the electromechanical properties of armchair boron nitride nanoribbons

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.

Structures and Electromagnetic Properties of Boron Nitride Nanoribbons Doped with Transition Metals

Inspired by the recent discovery of the Ti-doped BN nanocages, here we report the design of novel boron nitride (BN) nanoribbons (BNNRs) doped with fourth-row transition metals (Sc-Cu) and the prediction of their structural and electromagnetic properties. First-principles calculations and ab initio molecular dynamics simulations show that Ti-doped BNNR possesses both thermodynamic and kinetic stability at high temperatures for synthesis of BN materials. Metal doping may make the nonmagnetic pristine BNNR ferromagnetic or antiferromagnetic, depending on the metal. The doping with all considered metals reduces substantially the band gap of pristine BNNR. For example, Sc-doped BNNR is ferromagnetic with an indirect band gap of 1.18 eV, while V-doped nanoribbon is antiferromagnetic with a direct gap of 2.50 eV. Remarkably, the carrier mobility in both materials is significantly enhanced compared to the pristine BNNR. Our findings suggest that doping with different metals may endow BNNRs with versatile electronic and magnetic properties.

Optical properties of boron nitride nanoribbons with reconstructed edges

In this work, we employ first-principles calculations to investigate the optical properties of boron nitride nanoribbons with reconstructed edges. We found that because of the presence of homopolar B-B and N-N bonds in the edges, such nanoribbons, unlike boron nitride nanotubes, absorb light and have non-null optical conductivity in the low energy range. The stoichiometry and distribution of the homopolar bonds in the edges change the absorption, reflectance, refractive index, and optical conductivity of nanoribbons, which may allow the tuning of those properties. Regarding the absorption in the low energy range, the nanoribbons with B excess are almost unaffected by the direction of light incidence. On the other hand, the direction of light incidence strongly affects the intensity of the absorption peaks of nanoribbons with N excess in the region. At ultraviolet and above non-cylindrical geometry of the ribbons with the homopolar bonds at the edges also lead to a dependence of the optical properties with the direction of light incidence.

Thermoelectric properties study on the BN nanoribbons via BoltzTrap first-principles

Thermoelectric materials have attracted the attention of scientists because they directly convert waste heat of electric energy into valuable electrical energy. In recent years, the boron nitride structure has attracted much attention due to its thermoelectric properties and environmental friendliness. In this paper, the thermoelectric properties of boron nitride nanoribbons were simulated and analyzed, discovering that the figure-of-merit (ZT) value of armchair boron nitride nanoribbons is much better than that of zigzag boron nitride nanoribbons. Subsequently, we discuss the bandwidth effects and edge chirality on two important thermoelectric properties, Seebeck coefficient and ZT. Although edge passivation has been carried out, different edge chiralities still have a significant impact on carrier transport. The development of boron nitride-based materials will clarify their potential for developing high performance next generation thermoelectric devices.

Neurotransmitter-Functionalized Boron Nitride Nanoribbons as Biological Cargo Carriers: Analysis by Density Functional Theory

The structural and electronic properties of boron nitride nanoribbons (BNNRs) adsorbed with two neurotransmitters, dopamine (DA) and adrenaline (AD), have been systematically investigated using ele...

Thermo-mechanical properties of boron nitride nanoribbons: A molecular dynamics simulation study

Thermo-mechanical properties of boron nitride nanoribbons (BNNRs) were computed using molecular dynamics simulation with optimized Tersoff empirical potential. Thermal conductivity (TC) and heat transport properties of BNNRs were calculated as functions of both temperature and nanoribbon’s length. The results show that TC of BNNRs decreases with raising temperature by T−1.5 up to 1000K. The phonon–phonon scattering relaxation time, mean free path of phonons, and contribution of high frequency optical phonons in TC of BNNRs were calculated at various temperatures. TC decreases as nanoribbon size increases and it converges to ∼500Wm−1K−1 for nanoribbons with length longer than 30nm. The mechanical properties, including Gruneisen parameter, stress-strain response curves, Young’s modulus, intrinsic strength, critical strain, and poisson’s ratio were calculated in the temperature range of 137–1000K. The simulation results show that Gruneisen parameter and poisson’s ratio of BNNRs are −0.092 and 0.245, respectively. The Young’s modulus of BNNRs decreases with raising temperature and its value is 630GPa at 300K. According to the results, BNNRs duo to their extraordinary thermo-mechanical properties, are the promising candidate for the future nano-device manufacturing.

Size effects in mechanical properties of boron nitride nanoribbons

Size effects in mechanical properties are investigated through molecular dynamics simulations with Tersoff-like potential for boron nitride nanoribbons (BNNRs) in the armchair and zigzag directions under uniaxial tension. It is found that tensile properties of rectangular BNNRs of fixed lengths are significantly affected by the length-width ratios, while these aspect ratios are less sensitive to tensile properties of rectangular BNNRs of fixed widths. Size effects are minor in square boron nitride nanosheets. For zigzag BNNRs of fixed length, Young’s modulus, fracture stress and fracture strain increase when decreasing the width. For armchair BNNRs of fixed length, Young’s modulus and fracture strain increase, while fracture stress varies slightly when decreasing the width. Young’s modulus of zigzag BNNRs decreases from 299 N/m for a very narrow sheet to 258 N/m for square sheets, while this mechanical property increases from 231 N/m to 250 N/m for armchair BNNRs. Fracture stress of zigzag BNNRs decreases from 44.4 N/m for a very narrow sheet to 35.6 N/m for square sheet.

Electronic and optical properties of boron nitride nanoribbons in electric field by the tight-binding model

The tight-binding model is used to study the electronic and optical properties of armchair and zigzag boron nitride nanoribbons (ABNNRs and ZBNNRs) in electric field. Electric field could significantly change dispersion relations, degeneracy, edge-states, band crossings, and energy gaps. The field-modulation of energy gaps is more effective and covers wider energy range for BNNRs than graphene nanoribbons. The critical electric field that induces zero-gap transition strongly depends on geometric structures of BNNRs. At zero field, the selection rule and the absorption frequency range of spectral functions are different between ABNNRs and ZBNNRs. Electric field would change state functions that constructs new selection rule and further exhibits more absorption peaks.

Electronic and magnetic properties of boron nitride nanoribbons with square–octagon (4 | 8) line defects

The electronic and magnetic properties of boron nitride nanoribbons (BNNRs) with square–octagon (4 | 8) line defects (LD-(4 | 8)), parallel to their edges, have been investigated by first-principles calculations. It is found that the zigzag type LD-(4 | 8) BNNR with boron terminated edges is an antiferromagnetic (AFM‘ + − + −’) insulator with an indirect bandgap, but that with nitrogen terminated edges has two degenerate ground states with the same energy, among which one is ferromagnetic (FM ‘ + + + +’) half-metallic and the other is AFM ‘ + + − −’ metallic. In contrast, it is more interesting to find that the bare and fully-hydrogen terminated armchair edge BNNRs with unsymmetric (4 | 8) line defects have an indirect and direct gap, respectively, both of which show a characteristic three family oscillation behavior, depending only on the ribbon width in its narrower part, but not the whole BNNR’s width. Finally, the stabilities of a two-dimensional h-BN sheet with a zigzag or armchair type LD-(4 | 8) in it are further confirmed, among which the one with the armchair type LD-(4 | 8) is much more stable than that with the zigzag type counterpart.

Electronic and magnetic properties of boron nitride nanoribbons with topological line defects

Spin-polarized first-principles calculations show that in contrast to pristine boron nitride nanoribbons (BNNRs), the hybrid BNNRs with topological line defects exhibit diverse electronic and magnetic properties. It is interesting to find that with no need for selective edge functionalization, hybrid BNNRs can exhibit half-metallicity and half-semi-metallicity, dependent on the type of edge and line defect. Furthermore, an applied tensile strain can tune the half-semi-metal gap and stabilize the ferromagnetic ordering of the ground state. For hybrid BNNRs with two zigzag edges saturated, the tailoring of line defect state makes the band gap smaller. This work provides a possibility of making spintronic devices based on hybrid BNNRs with line defects and an interesting way of fabricating metal-free half-metal.

Asymmetric energy transport in defected boron nitride nanoribbons: Implications for thermal rectification

Using molecular dynamics simulations, the thermal transport properties of boron nitride nanoribbons (BNNR) containing geometrically-asymmetric triangular nano-vacancies were investigated. By suitably interpreting the time-evolution of spatially decomposed heat-current autocorrelation function in terms of phonon propagation characteristics, we have demonstrated the possibility of observing defect induced direction-dependent thermal transport in BNNR. This was further confirmed by appropriate analysis of direction dependent thermal diffusivity estimations in BNNR.

Optical properties of boron nitride nanoribbons: Excitonic effects

The optical properties of zigzag and armchair boron nitride nanoribbons (BNNRs) are investigated via a GW-Bethe-Salpeter equation approach. The reduced dimensionality and large band gaps of the BNNRs significantly enhance the exciton binding energies up to several eV. Many-body effects dramatically reshape the absorption spectra and excitonic peaks dominate the spectra. Moreover, the absorption spectra of zigzag BNNRs distinctly differ from those of armchair BNNRs, which can be as a signature to distinguish these two kinds of BNNRs experimentally. Dark excitons, stemming from dipole-forbidden transition, are also observed in BNNRs, which might greatly influence the luminescence yield of the system.

Effect of triangle vacancy on thermal transport in boron nitride nanoribbons

Recently, triangle vacancy in hexagonal boron nitride is observed experimentally. Using nonequilibrium Green’s function method, we investigate thermal transport properties of boron nitride nanoribbons (BNNRs) with a triangle vacancy. The effect of triangle vacancy on the phonon transmission of zigzag-edged BNNRs (Z-BNNRs) is different from that of armchair-edged BNNRs (A-BNNRs). The triangle vacancy induces antiresonant dips in the spectrum of Z-BNNRs. Moreover, the boron-terminated triangle vacancy causes antiresonant zero-transmission dip and the number of the zero-transmission dip increases with the geometrical size of triangle vacancy. For the A-BNNRs with triangle vacancy, except some antiresonant dips, a resonant peak is found in the transmission. The antiresonant and resonant phenomena are explained by analyzing local density of states and local thermal currents. Although the antiresonant dip and the resonant peak are both originated from quasibound states, their distributions of local thermal currents are distinct, which leads to the transport discrepancy. In addition, the thermal conductance of BNNRs decreases linearly with increasing the vacancy size.

Strain Effects on Electronic Properties of Boron Nitride Nanoribbons

We investigate the strain effects on the electronic properties of boron nitride nanoribbons (BNNRs) by using first-principles calculations. The results show that the energy gap of BNNRs with both armchair edges (A-BNNRs) and zigzag edges (Z-BNNRs) decreases as the strain increases. As strain increases, the energy gaps of Z-BNNRs decrease rapidly as the width increases and reduce significantly to small values, which makes Z-BNNRs change from wide-gap to narrow-gap semiconductors.

Energy Gaps and Stark Effect in Boron Nitride Nanoribbons

A first-principles investigation of the electronic properties of boron nitride nanoribbons (BNNRs) having either armchair or zigzag shaped edges passivated by hydrogen with widths up to 10 nm is presented. Band gaps of armchair BNNRs exhibit family dependent oscillations as the width increases and, for ribbons wider than 3 nm, converge to a constant value that is 0.02 eV smaller than the bulk band gap of a boron nitride sheet owing to the existence of very weak edge states. The band gap of zigzag BNNRs monotonically decreases and converges to a gap that is 0.7 eV smaller than the bulk gap due to the presence of strong edge states. When a transverse electric field is applied, the band gaps of armchair BNNRs decrease monotonically with the field strength. For the zigzag BNNRs, however, the band gaps and the carrier effective masses either increase or decrease depending on the direction and the strength of the field.