Structure Of Phosphorene Research Articles

Nine new phosphorene polymorphs with non-honeycomb structures: a much extended family.

We predict a new class of monolayer phosphorus allotropes, namely, ε-P, ζ-P, η-P, and θ-P. Distinctly different from the monolayer α-P (black) and previously predicted β-P (Phys. Rev. Lett. 2014, 112, 176802), γ-P, and δ-P (Phys. Rev. Lett. 2014, 113, 046804) with buckled honeycomb lattice, the new allotropes are composed of P4 square or P5 pentagon units that favor tricoordination for P atoms. The new four polymorphs, together with five additional hybrid polymorphs, greatly enrich the phosphorene structures, and their stabilities are confirmed by first-principles calculations. In particular, the θ-P is shown to be equally stable as the α-P (black) and more stable than all previously reported phosphorene polymorphs. Prediction of nonvolatile ferroelastic switching and structural transformation among different polymorphs under strains points out their potential applications via strain engineering.

Van der Waals heterostructure of phosphorene and graphene: tuning the Schottky barrier and doping by electrostatic gating.

In this Letter, we study the structural and electronic properties of single-layer and bilayer phosphorene with graphene. We show that both the properties of graphene and phosphorene are preserved in the composed heterostructure. We also show that via the application of a perpendicular electric field, it is possible to tune the position of the band structure of phosphorene with respect to that of graphene. This leads to control of the Schottky barrier height and doping of phosphorene, which are important features in the design of new devices based on van der Waals heterostructures.

Remarkably low-energy one-dimensional fault line defects in single-layered phosphorene.

Systematic engineering of atomic-scale low-dimensional defects in two-dimensional nanomaterials is a promising method to modulate the electronic properties of these nanomaterials. Defects at interfaces such as grain boundaries and line defects can often be detrimental to technologically important nanodevice operations and thus a fundamental understanding of how such one-dimensional defects may have an influence on their physio-chemical properties is pivotal for optimizing their device performance. Of late, two-dimensional phosphorene has attracted much attention due to its high carrier mobility and good mechanical flexibility. In this study, using density-functional theory, we have investigated the temperature-dependent energetics and electronic structure of single-layered phosphorene with various fault line defects. We have generated different line defect models based on a fault method, rather than the conventional rotation method. This has allowed us to study and identify new low-energy line defects, and we show how these low-energy line defects could well modulate the electronic band gap energies of single-layered two-dimensional phosphorene - offering a range of metallic to semiconducting properties in these newly proposed low-energy line defects in phosphorene.

Tiling phosphorene.

We present a scheme to categorize the structure of different layered phosphorene allotropes by mapping their nonplanar atomic structure onto a two-color 2D triangular tiling pattern. In the buckled structure of a phosphorene monolayer, we assign atoms in "top" positions to dark tiles and atoms in "bottom" positions to light tiles. Optimum sp3 bonding is maintained throughout the structure when each triangular tile is surrounded by the same number N of like-colored tiles, with 0≤N≤2. Our ab initio density functional calculations indicate that both the relative stability and electronic properties depend primarily on the structural index N. The proposed mapping approach may also be applied to phosphorene structures with nonhexagonal rings and 2D quasicrystals with no translational symmetry, which we predict to be nearly as stable as the hexagonal network.

Modulation of the Electronic Properties of Ultrathin Black Phosphorus by Strain and Electrical Field

The structural and electronic properties of the bulk and ultrathin black phosphorus and the effects of in-plane strain and out-of-plane electrical field on the electronic structure of phosphorene are investigated using first-principles methods. The computed results show that the bulk and few-layer black phosphorus from monolayer to six-layer demonstrates inherent direct bandgap features ranging from 0.5 to 1.6 eV. Interestingly, the band structures of the bulk and few-layer black phosphorus from X point via A point to Y point present degenerate distribution, which shows totally different partial charge dispersions. Moreover, strong anisotropy in regard to carrier effective mass has been observed along different directions. The response of phosphorene to in-plane strain is diverse. The bandgap monotonically decreases with increasing compressive strain, and semiconductor-to-metal transition occurs for phosphorene when the biaxial compressive reaches −9%. Tensile strain first enlarges the gap until the strai...

The potential application of phosphorene as an anode material in Li-ion batteries

The capacity and stability of the constituent electrodes critically determine the performance of Li-ion batteries (LIBs). In this study, density functional theory is employed to explore the potential application of the recently synthesized two dimensional phosphorene as an electrode material in LIBs. Our results show that Li atoms can bind strongly with the phosphorene monolayer and double layer with significant electron transfer. Besides, the structure of phosphorene is not influenced much by lithiation and the volume change is only 0.2%. After lithiation, a semiconductor-to-conductor transition is observed. The diffusion barrier values of Li are calculated to be 0.76 and 0.72 eV on monolayer and double layer phosphorene, respectively. We further demonstrate that the theoretical specific capacity of the phosphorene monolayer is 432.79 mA h g−1, which is larger than those of other commercial anode materials. The influence of Si and S implantation is also examined and our results indicate that Si-doped phosphorene greatly improves the binding of Li atoms, while the diffusion barrier is not affected. Our findings show that the high capacity, low open circuit voltage, small volume change and electrical conductivity of lithiated phosphorene make it a good candidate for application as an electrode material in batteries.

Strain-engineered direct-indirect band gap transition and its mechanism in two-dimensional phosphorene

Recently fabricated two dimensional (2D) phosphorene crystal structures have demonstrated great potential in applications of electronics. In this work, strain effect on the electronic band structure of phosphorene was studied using first principles methods. It was found that phosphorene can withstand a surface tension and tensile strain up to 10 N/m and 30%, respectively. The band gap of phosphorene experiences a direct-indirect-direct transition when axial strain is applied. A moderate -2% compression in the zigzag direction can trigger this gap transition. With sufficient expansion (+11.3%) or compression (-10.2% strains), the gap can be tuned from indirect to direct again. Five strain zones with distinct electronic band structure were identified and the critical strains for the zone boundaries were determined. The origin of the gap transition was revealed and a general mechanism was developed to explain energy shifts with strain according to the bond nature of near-band-edge electronic orbitals. Effective masses of carriers in the armchair direction are an order of magnitude smaller than that of the zigzag axis indicating the armchair direction is favored for carrier transport. In addition, the effective masses can be dramatically tuned by strain, in which its sharp jump/drop occurs at the zone boundaries of the direct-indirect gap transition.

Phosphorene as a Superior Gas Sensor: Selective Adsorption and Distinct I-V Response.

Recent reports on the fabrication of phosphorene, that is, mono- or few-layer black phosphorus, have raised exciting prospects of an outstanding two-dimensional (2D) material that exhibits excellent properties for nanodevice applications. Here, we study by first-principles calculations the adsorption of CO, CO2, NH3, NO, and NO2 gas molecules on a monolayer phosphorene. Our results predict superior sensing performance of phosphorene that rivals or even surpasses that of other 2D materials such as graphene and MoS2. We determine the optimal adsorption positions of these molecules on the phosphorene and identify molecular doping, that is, charge transfer between the molecules and phosphorene, as the driving mechanism for the high adsorption strength. We further calculated the current-voltage (I-V) relation using the nonequilibrium Green's function (NEGF) formalism. The transport features show large (1-2 orders of magnitude) anisotropy along different (armchair or zigzag) directions, which is consistent with the anisotropic electronic band structure of phosphorene. Remarkably, the I-V relation exhibits distinct responses with a marked change of the I-V relation along either the armchair or the zigzag directions depending on the type of molecules. Such selectivity and sensitivity to adsorption makes phosphorene a superior gas sensor that promises wide-ranging applications.