Transport Properties Of Phosphorene Nanoribbons Research Articles

Transport properties of phosphorene nanoribbons with defects

We have theoretically studied the electron transport properties in the phosphorene nanoribbons with different kinds of defects, including either single or multiple vacancies and substitutions, in comparison with otherwise perfect lattice. It is found that whether the transport channel would be destroyed or not is dependent on the defects' locations. If the defects locate on the original perfect current paths, the conductivity would decrease to zero at a certain Fermi energy. This is also confirmed by calculating the microscopic currents, which shows how the relative location, the number of defects and its severity affect the conductivity. The results are helpful for its application in the transport devices.

Tuning of the electronic structures and spin-dependent transport properties of phosphorene nanoribbons by vanadium substitutional doping

Based on vanadium-doped zigzag phosphorene nanoribbon (ZPNRs), we investigate the electronic structures and spin-dependent transport properties by the first-principles calculations in combination with the nonequilibrium Green's function approach. We find that the ZPNRs can be tuned from nonmagnetic metals to magnetic metals or half-metals by different doping positions, which are caused by the hybridization among different electron orbitals under the crystal field. Moreover, a robust negative differential resistance effect is observed in all studied devices, and a perfect spin-filter effect with almost 100% spin polarization can be found under low bias. We analyze the transport properties in detail from the viewpoint of the transmission spectrum and molecular energy levels. These results indicate that the vanadium-doped ZPNRs have potential applications as multi-functional spintronic devices. • Zigzag phosphorene nanoribbons can be tuned from nonmagnetic metals to magnetic metals or half-metals. • Robust negative differential resistance effect is observed. • Perfect spin-filter effect with almost 100% spin polarization can be found. • We analyze the transport properties in detail.

Bandstructure and Size-Scaling Effects in the Performance of Monolayer Black Phosphorus Nanodevices.

Nanodevices based on monolayer black phosphorus or phosphorene are promising for future electron devices in high density integrated circuits. We investigate bandstructure and size-scaling effects in the electronic and transport properties of phosphorene nanoribbons (PNRs) and the performance of ultra-scaled PNR field-effect transistors (FETs) using advanced theoretical and computational approaches. Material and device properties are obtained by non-equilibrium Green’s function (NEGF) formalism combined with a novel tight-binding (TB) model fitted on ab initio density-functional theory (DFT) calculations. We report significant changes in the dispersion, number, and configuration of electronic subbands, density of states, and transmission of PNRs with nanoribbon width (W) downscaling. In addition, the performance of PNR FETs with 15 nm-long channels are self-consistently assessed by exploring the behavior of charge density, quantum capacitance, and average charge velocity in the channel. The dominant consequence of W downscaling is the decrease of charge velocity, which in turn deteriorates the ON-state current in PNR FETs with narrower nanoribbon channels. Nevertheless, we find optimum nanodevices with W > 1.4 nm that meet the requirements set by the semiconductor industry for the “3 nm” technology generation, which illustrates the importance of properly accounting bandstructure effects that occur in sub-5 nm-wide PNRs.

Flexoelectricity and transport properties of phosphorene nanoribbons under mechanical bending

We examine from first principles the flexoelectric properties of phosphorene nanoribbons under mechanical bending along armchair and zigzag directions. In both cases we find that the radial polarization depends linearly on the strain gradient. The flexoelectricity along the armchair direction is over 40% larger than along the zigzag direction. The obtained flexoelectric coefficients of phosphorene are four orders of magnitude larger than those of graphene and comparable to transition metal dichalcogenides. Analysis of charge density shows that the flexoelectricity mainly arises from the ${p}_{z}$ orbitals of phosphorus atoms. The electron mobilities in bent phosphorene can be enhanced by over 60% along the armchair direction, which is significantly higher than previous reports of mobility tuned by uniaxial strain. Our results indicate phosphorene is a candidate for a two-dimensional material applicable in flexible-electronic devices.

Influence of edge passivation on the transport properties of the zigzag phosphorene nanoribbons

By using first-principles calculation based on density functional theory and non-equilibrium Green's function method, we investigate the transport properties of zigzag phosphorene nanoribbons (ZPNRs). The edges of the ZPNRs can be passivated in three ways named W1, W2, W3. These calculated results show that the electronic transport properties of the ZPNRs can be seriously influenced by the edge passivation ways, and the transport is determined by both the two edges and the interaction between them. Moreover, we find the width of the ZPNR can switch on or switch off the transport channel of the W3-type ZPNR. Furthermore, we present the transmission spectra, the band structures of both left and right electrodes, the molecular energy levels, and transmission eigenstates of the H-S-passivated W3-type ZPNRs to uncover the transport mechanism. This study provides a theoretical support for designing the related nanodevices by changing the passivation ways, which is an effective route for tuning the electronic structures and the transport properties of the phosphorene nanoribbons.

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.

Modulation of quantum transport properties in single-layer phosphorene nanoribbons using planar elastic strains

The influence of uniaxial and biaxial strains on electronic and transport properties of phosphorene nanoribbons (PNRs) is investigated within the tight-binding Green’s function theory by including an iterative procedure. For this purpose, we use tensile and compressive strains and employ the electronic band structure, effective mass and current–voltage curve, to explore the transport mechanism of PNR devices. Our results based on the band structure show that pseudogap in zigzag PNR (zPNR) is tunable under the strains. Hence, the tunneling transmission is controllable between two edge states of zPNRs. Obviously, we observe that the compressive strains can disturb the electron distributions leading to the induced charge polarization in armchair PNRs (aPNR). Also, in some particular cases there is massive–massless Dirac fermion transition in aPNRs. We found that the p-type zPNR devices can be designed under the compressive strains and the n-type aPNR devices can be modulated under the tensile strains. Our results show that the strains can be used as a way to control and improve the negative differential resistance phenomena in zPNRs. In aPNRs the current and threshold voltage under a finite bias can be changed several times with the uniaxial and biaxial strains. Thus, PNRs can be utilized for the development of flexible electronic and field effect transistor nanodevices.

Publisher's Note: Structural, electronic, mechanical, and transport properties of phosphorene nanoribbons: Negative differential resistance behavior [Phys. Rev. B 94 , 075422 (2016)

Received 11 June 2018DOI:https://doi.org/10.1103/PhysRevB.97.239902©2018 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElasticityPhysical SystemsDevicesMulticomponent & negative-ion plasmaNanoribbonPhosphoreneTechniquesDensity functional calculationsCondensed Matter, Materials & Applied Physics

Tuning of the electronic and transport properties of phosphorene nanoribbons by edge types and edge defects

By performing first-principle quantum transport calculations, we investigated the effects of the edge types and edge defects on the electronic and transport properties of phosphorene nanoribbons (PNRs). The calculated band structures show the PNRs with the zigzag and cliff edges are all metallic. The conductance of the cliff phosphorene nanoribbon (CPNR) is higher than that of the zigzag phosphorene nanoribbon (ZPNR). The low bias negative differential resistance behavior is only found in the ZPNR and the peak-to-valley current ratio is up to 102. More over, we found the carrier transport channels under low bias of ZPNR and CPNR mainly locate on the edges. The current-voltage characteristics show the defects induced by removing the phosphorus atoms from the edge can decrease the conductance of the ZPNR and CPNR obviously. The low bias negative differential resistance behavior of the ZPNR also can be weakened or removed by the edge defects.

Structural, electronic, mechanical, and transport properties of phosphorene nanoribbons: Negative differential resistance behavior

Structural, electronic, mechanical, and transport properties of two different types of phosphorene nanoribbons are calculated within the density functional theory and nonequilibrium Green's function formalisms. Armchair nanoribbons turn out to be semiconductors at all widths considered. Zigzag nanoribbons are metallic in their layer-terminated structure, but undergo Peierls-like transition at the edges. Armchair nanoribbons have smaller Young's modulus compared to a monolayer, while zigzag nanoribbons have larger Young's modulus. Edge reconstruction further increases the Young's modulus of zigzag nanoribbons. A two-terminal device made of zigzag nanoribbons show negative differential resistance behavior that is robust with respect to edge reconstruction. We have also calculated the $I\text{\ensuremath{-}}V$ characteristics for two nonzero gate voltages. The results show that the zigzag nanoribbons display strong $p$-type character.

Immunity of electronic and transport properties of phosphorene nanoribbons to edge defects

We present an extensive study of the electronic properties and carrier transport in phosphorene nanoribbons (PNRs) with edge defects by using rigorous atomistic quantum transport simulations. This study reports on the size- and defect-dependent scaling laws governing the transport gap, and the mean free path and carrier mobility in the PNRs of interest for future nanoelectronics applications. Our results indicate that PNRs with armchair edges (aPNRs) are more immune to defects than zig-zag PNRs (zPNRs), while both PNR types exhibit superior immunity to defects relative to graphene nanoribbons (GNRs). An investigation of the mean free path demonstrated that even in the case of a low defect density the transport in PNRs is diffusive, and the carrier mobility remains a meaningful transport parameter even in ultra-small PNRs. We found that the electron–hole mobility asymmetry (present in large-area phosphorene) is retained only in zPNRs for W > 4 nm, while in other cases the asymmetry is smoothed out by edge defect scattering. Furthermore, we showed that aPNRs outperform both zPNRs and GNRs in terms of carrier mobility, and that PNRs generally offer a superior mobility-bandgap trade-off, relative to GNRs and monolayer MoS2. This work identifies PNRs as a promising material for the extremely scaled transistor channels in future post-silicon electronic technology, and presents a persuasive argument for experimental work on nanostructured phosphorene.

Electronic and transport properties of phosphorene nanoribbons

By combining density functional theory and nonequilibrium Green's function, we study the electronic and transport properties of monolayer black phosphorus nanoribbons (PNRs). First, we investigate the band gap of PNRs and its modulation by the ribbon width and an external transverse electric field. Our calculations indicate a giant Stark effect in PNRs, which can switch on transport channels of semiconducting PNRs under low bias, inducing an insulator-metal transition. Next, we study the transport channels in PNRs via the calculations of the current density and local electron transmission pathway. In contrast to graphene and ${\mathrm{MoS}}_{2}$ nanoribbons, the carrier transport channels under low bias are mainly located in the interior of both armchair and zigzag PNRs, and immune to a small amount of edge defects. Last, a device of the PNR-based dual-gate field-effect transistor, with high on/off ratio of ${10}^{3}$, is proposed based on the giant electric-field tuning effect.