Armchair Phosphorene Nanoribbons Research Articles

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.

Effects of spin-orbit coupling on transmission and absorption of electromagnetic waves in strained armchair phosphorene nanoribbons.

We compute the optical conductivity, both the imaginary and real parts of the dielectric constant, and the optical coefficients of armchair phosphorene nanoribbons under application of biaxial and uniaxial strains. The Kane-Mele model Hamiltonian has been applied to obtain the electronic band structure of phosphorene nanoribbons in the presence of a magnetic field. The effects of uniaxial and biaxial in-plane strain on the frequency behavior of the optical dielectric constant, and the frequency behavior of the optical absorption and refractive index of phosphorene nanoribbons have been studied, in terms of magnetic field, spin-orbit coupling and strain effects. Linear response theory and the Green's function approach have been exploited to obtain the frequency behavior of the optical properties of the structure. Moreover, the transmissivity and reflectivity of electromagnetic waves between two media separated by a phosphorene-nanoribbon layer are determined. Our numerical results indicate that the frequency dependence of the optical absorption includes a peak due to applying a magnetic field. Moreover, the effects of both in-plane uniaxial and biaxial strains on the refractive index of single-layer phosphorene have been addressed. Also, the frequency dependence of the transmissivity and reflectivity of electromagnetic waves between two media separated by armchair phosphorene nanoribbons for normal incidence has been investigated in terms of the effects of magnetic field and strain parameters. Both compressive and tensile strain have been considered for the armchair phosphorene nanoribbons in order to study the optical properties of the structure. In particular, the control of the optical properties of phosphorene nanoribbons could lead to extensive applications of phosphorene in the optoelectronics industry. Also, such a study of the optical properties of phosphorene nanoribbons has further applications in light sensors. Meanwhile, the effects of spin-orbit coupling on the optical absorption and transmissivity of electromagnetic waves in phosphorene nanoribbons could be a novel topic in condensed-matter physics.

Interface design of the thermoelectric transport properties of phosphorene-tetrathiafulvalene nanoscale devices.

Interface design and energy band engineering are two key strategies for improving the thermoelectric conversion efficiency of low dimensional nanoscale devices. By using first-principle-based density functional theory combined with a non-equilibrium Green function method, the thermoelectric properties of a single tetrathiafulvalene (TTF) molecule coupled with armchair phosphorene nanoribbons (APNRs) within different interface modes have been investigated. The results indicate that phonon transport can be dramatically suppressed in this intermediate weak-coupling system due to strong interfacial phonon scattering behavior, where very few phonons can propagate through two nonbonded interface regions from left side lead to a TTF molecule and then to right side lead. Furthermore, connecting a thiophene group at both the head and tail of the intermediate TTF molecule can significantly enhance the power factor (S2σ) of such a weak-coupling system based on an out-of-plane electronic transmission mechanism, and there is obvious charge transfer from S atoms to upper and lower APNRs. Compared to a single regular method, composite interface co-design can achieve more accurate control of thermal/electrical transmission performance. Electrical conductance can be effectively improved with low phonon thermal conductance being maintained at the same time, and an excellent thermoelectric figure of merit (ZT) of 0.73 has been obtained near 0.6 eV.

Width and split effects on effective spin flip through armchair phosphorene nanoribbons

Width and split effects on effective spin flip through armchair phosphorene nanoribbons

Performance study of tunneling field effect transistors based on the graphene and phosphorene nanoribbons

The present work deals with the simulation and comparison of two tunneling field effect transistors (TFETs) based on the single layers of armchair graphene nanoribbons (AGNRs) and armchair phosphorene nanoribbons (APNRs). The transmission properties of the transistor have been obtained by solving the Schrödinger-Poisson equations self-consistently using the non-equilibrium Green's function (NEGF) formalism and the real-space approach. In addition, the energy band structure of the two materials have been obtained using tight-binding approximation method. The simulation results in each bias include the energy band structure, energy-resolved current spectrum, transmission function and drain current versus gate voltage diagrams. The results indicate that the structure of phosphorene TFETs meets a better ION to IOFF ratio and sub-threshold swing than the graphene TFETs despite a relative decrease in the amount of ION.

The effect of edge passivation of phosphorene nanoribbons with different atoms and arrangements on their electronic and transport properties

Through density functional theory (DFT), we investigate the electronic and transport properties of zigzag phosphorene nanoribbons (ZPNRs) and armchair phosphorene nanoribbons (APNRs) passivated with only H or O, or both H and O with different arrangements, systematically. According to the calculated cohesive energies, all structures are stable. Also, the simulation results reveal a semiconductor-to-metal transition in zigzag groups, but all the APNRs are semiconductors. We see the direct-to-indirect energy bandgap transition in armchair groups, while all the semiconductors of zigzag groups have a direct energy bandgap. We also study the effect of external transverse electric field on electronic properties. The applying electric field changes the energy bandgap leading to a semiconductor-to-metal transition at a certain electric field. In addition, the direct-to-indirect bandgap transition and vice versa occurs for some samples. Moreover, edge passivation has a significant effect on transport properties. The breakdown voltage of the devices changes from 0 to 1.94 eV, and we observe negative differential resistance (NDR) for some devices. The results indicate that passivated phosphorene nanoribbons are possible, and their properties can effectively be tuned by the arrangement, type of edge atoms, and external electric field, which make these structures a promising candidate for feasible nanodevices.

Force-constant model for the vibrational modes in black-phosphorene and phosphorene nanoribbons (PNRs)

We present in this paper, force constant model developed for Black phosphorene in order to reproduce the vibrationnal properties calculated from density functional theory. The results of this model are compared with the experimental data available from Raman spectroscopy measurements. Excellent agreement is obtained between calculation and Raman experiment. On the basis of the resulting force model, the non-resonant Raman spectra of a large number of armchair and zigzag phosphorene nanoribbons (PNRs) are calculated using the bond polarizability model in the framework of spectral moments method. We have found a good agreement with group theory concerning the number of the Raman-active modes of black phosphorene. We report the effect of the edge and width on the vibrational properties of PNRs by increasing the width, the main characteristic feature is dictated by Ag2 Raman active mode. It exhibits different characteristic for armchair and zigzag edges. The mode is upshifted under armchair edge and downshifted in the zigzag one. Moreover, we observe additional Raman modes as a function of the ribbon width and we propose an equation, ωmin = A/L (A = 98 cm−1 nm), to estimate the PNRs width L from the knowledge of the lowest Raman frequency mode ωmin.

Thermoelectric properties of armchair phosphorene nanoribbons in the presence of vacancy-induced impurity band

Armchair phosphorene nanoribbons (APNRs) are known to be semiconductors with an indirect bandgap. Here, we propose to introduce new states in the gap of APNRs by creating a periodic structure of vacancies (antidots). Based on the tight-binding model, we show that a periodic array of vacancies or nanopores leads to the formation of an impurity band inside the gap region. We first present an analytical expression for the dispersion relation of an impurity band induced by hybridization of bound states associated with each single vacancy defect. Then, we increase the size of vacancy defects to include a bunch of atoms and theoretically investigate the effect of nanopores size and their spacing on electronic band structure, carrier transmission function, and thermoelectric properties. Our analysis of the power generation rate and thermoelectric efficiency of these structures reveals that an ANPR can be used as a superb thermoelectric power generation module.

Electronic properties of multilayer armchair phosphorene nanoribbons under strain

We study the electronic properties of multilayer armchair phosphorene nanoribbons (APNRs) modulated by certain strains. The band structure is calculated by solving the corresponding differential Schrödinger equation, and the density of states (DOS) is obtained combining the Green's function method. It is found that the certain strain has similar effects on different layer APNRs. The vertical tensile strain along the z -direction, the compressive uniaxial strain along the y -direction and biaxial strain along the xy -direction can close the band gap. The gap disappears and some peaks appear around at the energy position of the band gap closure for the corresponding DOS. Further, it is shown that the band gaps depend linearly on the strain for all APNRs. However, the band structure and DOS for four layer APNR are most sensitive to the strains among all APNRs. Both the band gap and DOS variations with the strain show an insulator-metal transition induced by the strain for APNRs. Our results show that the four layer APNR are most suitable for the usage of electromechanical field effect transistors or detectors for detecting the strains. • The certain strain has similar effects on different layer APNRs. • The gap disappears and some peaks appear around at the energy position of the band gap closure for the corresponding DOS. • The band gaps depend linearly on the strain for all APNRs, the band structure for four layer APNR are most sensitive to the strains among all APNRs. • Both the band gap and DOS variations with the strain show an insulator-metal transition induced by the strain for APNRs.

Strain and electric field tunable electronic transport in armchair phosphorene nanodevice with normal-metal electrodes

Phosphorene, one of the graphene counterparts, is believed to have promising potential to be utilized in nanoelectronics due to its significant properties. Phosphorene has a nonplanar puckered structure with high anisotropy, which enables the elastic strain or external field to tune its electronic structure. In this work, we propose a nanodevice model based on an armchair phosphorene nanoribbon (APNR) with normal-metal electrodes and study the tuning effect of elastic strain and electric field on the electronic transport properties. We first confirm that the APNR can be driven to be of metallic conduction with linear dispersion around the Fermi level, by applying a critical compressive strain. After applying a perpendicular electric field, the APNR turns out to be a band insulator. Furthermore, we calculate the dc conductance and density of states (DOS) of the nanodevice, where the APNR is connected to normal-metal electrodes. The numerical results show that in the absence of an electric field, the nanodevice possesses peak values of conductance and DOS at the Fermi level. Once the electric field is applied, a gap emerges around the Fermi level in the conductance, which suggests that the nanodevice is turned off by the external electric field. Our investigation on the present system could be useful in the development of a field-effect nanodevice based on monolayer phosphorene.

Large positive and negative magnetoresistance in armchair phosphorene nanoribbons

We investigate the tunnel magnetoresistance (TMR) in an armchair phosphorene nanoribbon modulated by two ferromagnetic stripes. It is shown that large TMR can be achieved by applying a perpendicularly electric field to the phosphorene plane. We find that the TMR can be adjusted by an external gate voltage, and the TMR oscillates periodically from positive to negative by a slight change of the gate voltage. This characteristic can be observed in a wide region of exchange splitting values. Our findings open the way to design phosphorene-based spintronics nanodevices, and it may contribute to the future low power spintronic applications.

Influence of edge functionalization on electronic and optical properties of armchair phosphorene nanoribbons: a first-principles study

In this work, we present a systematic first-principles density-functional theory based study of geometry, electronic structure, and optical properties of armchair phosphorene nanoribbons (APNRs), with the aim of understanding the influence of edge passivation. Ribbons of width ranging from 0.33 nm to 3.8 nm were considered, with their edges functionalized with the groups H, OH, F, Cl, S, and Se. The geometries of various APNRs were optimized, and the stability was checked by calculating their formation energies. Using the relaxed geometries, calculations of their band structure and optical properties were performed. Pristine APNRs, as expected, exhibit significant edge reconstruction, rendering them indirect band gap semiconductors, except for one width (N = 5, where N is the width parameter) for which a direct band gap is observed. The edge passivated APNRs are found to be direct band gap semiconductors, with the band gap at the Γ-point, for all the functional groups considered in this work. To obtain accurate estimates of band gaps, calculations were also performed using HSE06 hybrid functional for several APNRs. Our calculations reveal that functional groups have significant influence on the band gaps and optical properties of narrower APNRs. For wider passivated ribbons, with the increasing ribbon widths, the gaps converge to almost the same value, irrespective of the group. We also performed calculations including the spin–orbit coupling (SOC) for hydrogen passivated APNRs with N = 5 and 11. We found that SOC has no significant influence on the band structure of the studied APNRs. However, for the broader APNR, a lowering of peak intensities was observed in the optical absorption spectrum beyond 5 eV.

The effect of strain on the zigzag and armchair phosphorene nanoribbon

Abstract In this work, the band structure and electronic properties of different nanoribbons of phosphorene along two typical crystal directions of armchair (AM) and zigzag (ZZ) were investigated under compression and tensile strain by density functional theory. The results were compared to the band structure and electronic properties of phosphorene monolayer at similar conditions. The electronic properties of armchair nanoribbons revealed to be resistant to tensile strain in the direction of the armchair, consistent to phosphorene monolayer, but they undergo band structure change due to the applied compression strain at armchair direction. By comparing the effects of strain on the zigzag nanoribbon and phosphorene monolayer, it was found that the zigzag direction neither tolerates the tensile strain nor resists compression strain.

Defect engineering on the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons**Project supported by the National Natural Science Foundation of China (Grant Nos. 11574080 and 91833302).

We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons (APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs. Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.

Design of spin-filtering devices with rectifying effects and negative differential resistance using armchair phosphorene nanoribbon

In the present work, we employ density functional theory in combination with non-equilibrium Green function to investigate the spin transport properties of six types of armchair phosphorene nanoribbons (APNRs) devices, i.e., M1–M6, in which the left and right electrodes are doped with different transition metal (TM) atoms such as Fe, Co, and Ni atoms. The M1, M3, and M5 devices are obtained by substituting (Co and Ni), (Fe and Co), (Fe and Ni) atoms, respectively, with the first atom (for example, Co in M1) placed in the center of the left and the other one (for example, Ni in M1) placed in the center of right electrode. Furthermore, the M2, M4, and M6 devices are obtained by moving the substitution sites of (Co and Ni), (Fe and Co), and (Fe and Ni) near the edge of NRs, respectively. In this study, APNRs with the widths of n = 7, 8, and 9 are chosen to study the effects of various widths of APNRs on their electronic transport properties. The current–voltage characteristics, rectification ratio and spin-filtering efficiency are calculated for the assumed devices. Our findings demonstrate that M3 and M5 devices in all considered widths represent 100% spin-filtering efficiency in dual-orientation of positive and negative bias. Besides, spin-dependent rectifying behavior is observed in our assumed systems. Also, all devices reveal spin-dependent negative differential resistance. Based on the obtained results, these phenomena can be manipulated by moving the positions of TM atoms from the center to the edge of NRs or changing the width of APNRs. Overall, our research may be helpful in designing multifunctional spintronic devices.

Improvement of H2O detection in armchair phosphorene nanoribbons by introducing dopant

Abstract Adsorption of H2O molecule on different substrates including pristine, B-, N-, Al-, Si- and S-doped APNRs is theoretically investigated using density functional theory in combination with non-equilibrium Green's function. The results show that there is a strong interaction between H2O and the Al-doped APNR due to high adsorption energy and short distance of Al-doped APNR from H2O. We find that the pristine, B-, N-, Al- and Si-doped APNRs are electron acceptor in presence of H2O molecule, while the S-doped APNR is donor. Our findings demonstrate that H2O molecule is weakly adsorbed on the pristine and N-doped APNRs and it affects electronic properties of these systems slightly. However, the adsorption of H2O induces dramatic changes on the electronic properties of Al-, Si- and S-doped APNRs. The results reveal that maximum sensitivities are 19.36%, 19.78%, 19.47%, 46%, 39%, and 34% for the pristine, B-, N-, Al-, Si- and S-doped APNRs at the bias voltage of 2 V, respectively. In this work, the Al-doped APNR is proposed as a promising material for H2O detection.

Quantum conductance of defected phosphorene and germanene nanoribbons

The electronic and transport properties of the monolayer black phosphorus and germanene nanoribbons are studied in the framework of the tight-binding model (TBM) based upon Landauer-Buttiker formalism using Green’s function method (GFM). The local density of states (LDOS) and electronic conductance of the phosphorene and germanene nanoribbons along zigzag and armchair directions are examined when the various types of defects are introduced into the system. It is found that the transport properties of zigzag phosphorene and germanene nanoribbons are strongly dependent on the number and location of the vacancies. Furthermore, it is shown that the one-/three-atom vacancy induces quasi-states in the conductance around the Fermi energy because of breaking the sublattice symmetry in the zigzag germanene nanoribbons (ZGeNRs). So the metal-semiconductor transition occurs when one-/three-atom vacancy is located at the edges of ZGeNRs; however, this transition is not observed in the zigzag phosphorene nanoribbons (ZPNRs). Besides, the results of the calculations indicate more sensitivity of ZPNRs on conductivity to the edge vacancy disorders than armchair phosphorene nanoribbons (APNRs). In addition, the conductance of ZPNRs decreases with the increment of the ribbon width in the presence of edge vacancy. Importantly, the disappearance of conductance around Fermi energy in ZPNR due to Anderson localization disorder highlights an important conclusion for the possibility of quenching of the conductance near the Fermi energy, making this class of materials appealing for applications in digital transistor devices.

Spin polarized electronic and optical properties of vacancy defects in armchair phosphorene nanoribbons

Using first-principles density functional theory, spin dependent electronic and optical properties of Armchair Phosphorene Nanoribbons (APNRs) with different widths (W = 8, 9, 10, 11) are investigated in presence of vacancy defects including of SV1, SV2, DV1, DV2 and DV3. The results show that geometric structures of APNRs, type and position of defects are essential factors in determining the electronic, magnetic and optical properties of APNRs. It is observed that 8, 9, 10 and 11APNRs in presence of the SV1 or SV2 defects are magnetic. However, DV1, DV2 and DV3 in APNRs with different widths can lead to non magnetic semiconductor with direct or indirect band gap. In addition, the effect of various defects concentrations (C = 1.38, 1.13 and 0.92%) is studied on the electronic and optical properties of 9APNR. The results show that the value of defect concentration can tune the electronic, magnetic and optical properties of 9APNRs. In all considered systems, the optical properties exhibit the strong anisotropic behaviors with respect to direction of light polarization. All these theoretical observations would open up possibilities for applications of APNRs in spintronic and optoelectronic devices.

Individual Identification of DNA Nucleobases on Atomically Thin Black Phosphorene Nanoribbons: van der Waals Corrected Density Functional Theory Calculations

Monolayer-based nanodevices hold great promise for the next-generation sequencing (biomolecular sensing/DNA sequencing)-based applications. In this study, we have investigated the interaction of the four nucleobases (adenine, guanine, thymine, and cytosine) on a phosphorene nanoribbon-based device armchair phosphorene nanoribbon (APNR) for individual identification of DNA nucleobases. Using the van der Waals corrected (PBE + vdW) density functional theory calculations, we have computed and analyzed the effect of interaction on the transmission properties of the APNR-based nanodevice. The change in the electronic transport properties of APNR when nucleobases are physisorbed has been investigated by using the nonequilibrium Green’s function calculations. The coupling strength is different to some extent for different nucleobases, resulting in different transmission dips due to Fano resonance.

The electronic and transport properties of the phosphorene nanoribbons

The electronic and transport properties of phosphorene nanoribbons with different edges and widths are studied by using the first-principles calculations together with non-equilibrium Green’s function. The band structures of zigzag phosphorene nanoribbons(ZPNRs) show the metallic characteristics when the nanoribbon width is over 6. But for the armchair phosphorene nanoribbons(APNRs), its band gap gradually decrease when the nanoribbon width is over 2. It can be found that both APNRs and ZPNRs appear negative differential resistance (NDR), namely, there is great potential in designing nanoelectronic devices.