Phosphorene Allotropes Research Articles

Large-scale synthesis of defect-free phosphorene on nickel substrates: enabling atomistic thickness devices

Addressing the main challenges of defect-free, large-scale synthesis of low-dimensional materials composed of phosphorus atoms is essential for advancing promising phosphorene-based technologies. Using molecular dynamics simulation, we demonstrate the large-scale and defect-free synthesis of phosphorene on Nickel (Ni) substrates. We showed that substrate orientation is crucial in the controllable synthesis of different phosphorene allotropes. Specifically, blue phosphorene was successfully grown on Ni (111) and Ni (100) surfaces, while γ-phosphorene, referred to here as Navy phosphorene, was grown on Ni (110). In addition, temperature control (high temperature) and cooling rate (slow cooling) are also crucial in the formation of P6 hexagons. Finally, we report that the phosphorus pentamers (P5) are the essential precursor for phosphorene synthesis. This work provides a robust framework for understanding and controlling the synthesis of large-area, single-crystalline monolayer phosphorene.

Electrostatic Gating of Phosphorene Polymorphs.

The ability to directly monitor the states of electrons in modern field-effect transistors (FETs) could transform our understanding of the physics and improve the function of related devices. In particular, phosphorene allotropes present a fertile landscape for the development of high-performance FETs. Using density functional theory-based methods, we have systematically investigated the influence of electrostatic gating on the structures, stabilities, and fundamental electronic properties of pristine and carbon-doped monolayer (bilayer) phosphorene allotropes. The remarkable flexibility of phosphorene allotropes, arising from intra- and interlayer van der Waals interactions, causes a good resilience up to equivalent gate potential of two electrons per unit cell. The resilience depends on the stacking details in such a way that rotated bilayers show considerably higher thermodynamical stability than the unrotated ones, even at a high gate potential. In addition, a semiconductor to metal phase transition is observed in some of the rotated and carbon-doped structures with increased electronic transport relative to graphene in the context of real space Green's function formalism.

Rippled blue phosphorene with tunable energy band structures and negative Poisson’s ratio

Recent successes in the discovery of novel two-dimensional (2-D) phosphorene allotropes have motivated more in-depth investigations into tuning their properties through precise geometric control. This is also driven by the fact that these materials, particularly blue phosphorene, are highly prone to wrinkling. In this work, we systematically study the mechanical and electronic behaviors of a series of rippled blue phosphorene PN (N = 8, 18, 32, 50, 72, 98) using density functional theory combined with molecular dynamic simulations. A novel approach to tailor the electronic energy band structure of blue phosphorene is proposed by wrinkle engineering, transforming the native indirect bandgap into a direct bandgap, and enabling bandgap tuning by modifying the undulation magnitude ratio. Furthermore, the mechanical behaviors of rippled blue phosphorene differ significantly along the 4-8-4 and 4-4-4 directions. Notably, negative Poisson’s ratio is observed under tension along the 4-4-4 direction. This work demonstrates new techniques for geometrically regulating blue phosphorene and potentially other 2-D materials. The findings also yield valuable insights for the design of novel 2-D auxetic semiconductors with tunable electronic properties.

Electro-osmotic flow in different phosphorus nanochannels

The electrokinetic transport in a neutral system consists of an aqueous NaCl solution confined in a nanochannel with two similar parallel phosphorene walls and is investigated for different black, blue, red, and green phosphorene allotropes in the presence of an external electric field in the directions x (parallel to the walls roughness axis) and y (perpendicular to the walls roughness axis). The results show that irrespective of the electric field direction, the thickness of the Stern layer increases with the increase in the magnitude of the negative electric surface charge density (ESCD) on the nanochannel walls, and it also increases with the increase in the roughness ratio for different allotropes. Moreover, three different regimes of Debye–Hückel (DH), intermediate, and flow reversal appear as the absolute value of the negative ESCD on the walls grows. With the increase in the absolute value of the negative ESCD, in the DH regime, the flow velocity grows, then in the intermediate regime, it decreases, and finally, at sufficiently high ESCD, the flow reversal occurs. When the external electric field is applied in the y direction, the dynamics of the system are slower than that of the x direction; therefore, the flow reversal occurs at the smaller absolute values of the negative ESCD.

Modelling of disclinated phosphorene crystals

In this article, the disclinated modifications of two-dimensional phosphorene crystals are modelled. The modelling technique explores the crystal lattices of disclinated graphenes known as pseudo-graphenes to form a family of materials sharing the same lattice structure and symmetry. To design crystal lattice of disclinated phosphorenes Ph5-7v1 and Ph5‑6‑7v2, the structures of pseudo-graphenes G5-7v1 and G5‑6‑7v2 are chosen as reference ones, respectively. Optimization procedure done with density functional theory (DFT) calculations proves that the designed lattices of disclinated phosphorenes are structurally stable that allows to analyze the band structure of phosphorene allotropes under consideration.

Super-high carrier mobilities and excellent thermoelectric performances of Tri-Tri group-VA monolayers.

High-performance thermoelectric materials in theoretical and experimental research are mostly composed of expensive, scarce, heavy elements and rarely of single light elements, which severely limit their application and development. Based on density functional and semiclassical Boltzmann transport theory, we determine that a stable phosphorene allotrope, named Tri-Tri phosphorene, has super-high electron mobility (23845.29 cm2 V-1 s-1) much higher than those of most two-dimension materials. Moreover, its optimized maximum ZT can reach up to 3.43 at room temperature (4.83 at 500 K and 5.92 at 700 K), exhibiting highly favorable prospects in practical thermoelectric systems. Motivated by the excellent properties of Tri-Tri phosphorene, we further demonstrate the structural stability of Tri-Tri arsenene and Tri-Tri antimonene and predict that the two Tri-Tri structures also have high Seebeck coefficients and electron mobilities. Their lattice thermal conductivities are dramatically decreased compared with Tri-Tri phosphorene. Thus, their predicted thermoelectric performances are also excellent, with maximum ZT values of 4.12 (Tri-Tri arsenene) and 3.54 (Tri-Tri antimonene) at room temperature. The low layer moduli of the three Tri-Tri structures indicate that they have high mechanical flexibility and suitability for current device assemblies. All these desirable properties make Tri-Tri group-VA materials promising for future applications in thermoelectric devices.

Unique low-energy line defects and lateral heterostructures in phosphorene

Defect engineering and heterostructure construction are important approaches to modulate the properties of two-dimensional semiconductors. We introduced four phosphorene allotropes as the defective structures to construct the corresponding line defects and lateral heterostructures in black phosphorene. In all the constructed phosphorene systems, the P atoms at the boundaries will keep local threefold covalent bonding, forming clean one-dimensional interfaces and exhibiting a high stability. Electronic structure calculations show that all the constructed structures are semiconducting in absent of deep defect states and the band gap values can be regulated by introducing different defective structures. Distinct distributions of the electronic frontier states are found in the different line defect systems and both type-I and II band alignments can be formed in the semiconducting lateral heterostructures.

Strong Optical Excitation and High Thermoelectric Performance in 2D Holey‐Phosphorene Monolayer

Through density functional theory (DFT)‐based computations, a systematic exploration of the newly predicted 2D phosphorene allotrope, namely holey‐phosphorene (HP), is carried out. It is revealed that HP shows a semiconducting nature with an indirect bandgap of 0.83 eV upon Perdew‐Burke‐Ernzerhof (PBE) functional. Then, to survey the optical features, a (G0W0)‐based approach is employed to solve the Bethe–Salpeter equation to derive the intra‐layer excitonic effects. It is derived via the absorption spectrum, that HP presents an excitonic binding strength of 1.47/1.96 eV along the x/y‐direction with the first peak of the absorption at 0.92/0.43 eV for the x/y‐direction. The thermoelectric properties are also explored in detail and reveal a very high thermal power value along with an enhanced figure of merit (ZT) of about 3.6. The 2D HP monolayer for thermoelectric performance has high thermoelectric conversion efficiency (TCE) and is estimated to be about 22. All these outstanding findings may be attributed to the quantum confinement effect of the porous geometry of the 2D HP nanosheet, thereby confirming its relevance as a prospect for high‐performance optoelectronic and thermoelectric engineering systems.

A new phosphorene allotrope: the assembly of phosphorene nanoribbons and chains.

Phosphorene allotrope monolayers such as blue and red phosphorus are being designed and synthesized to be used in the optoelectronics field due to their tunable bandgap and high mobility. Using the organic molecule self-assembly method similar to the synthesis of graphene allotropes, a novel phosphorene allotrope, P567 monolayer, with five-, six-, and seven-membered rings is designed through the assembly of black phosphorus chains and blue phosphorene nanoribbons. Ab initio molecular dynamics, phonon dispersion, and elastic constants demonstrate the dynamic, thermal, and mechanical stability of the P567 monolayer. Additionally, the first-principles calculations show that the P567 monolayer is an indirect bandgap semiconductor with moderate bandgap and high anisotropic mobility (4.47 × 103 cm2 V-1 s-1). Compared with black phosphorene, the suitable band edge position and higher optical absorption coefficient (105 cm-1) make the P567 monolayer more likely to be used as a photocatalytic hydrolysis material. The P567 monolayer is a viable candidate for use in innovative optoelectronic devices and the assembly method provides a rational approach to designing phosphorus allotropes with high photocatalytic efficiency.

New Pentaoctite Phase of Group‐V Nanostructures

By performing first‐principles electronic structure calculations, a new 2D pentaoctite phase of group‐V allotropes of antimonene, arsenene, and phosphorene is proposed. By calculating the phonon‐spectra, it is shown that these new materials are stable. In addition, these calculations reveal anisotropic elastic properties. Whereas these nanostructures in the pentaoctite phase exhibit indirect bandgaps, they can be made direct gap materials by applying an external strain. GW calculations of the dielectric function demonstrate that all these structures have an absorption spectrum in the visible region, which can be useful for group‐V optoelectronics.

An ab-initio study of blue phosphorene monolayer: Electronic, vibrational and optical properties

Recently, group-V two-dimensional (2D) monolayer elements, notably the novel allotropes of antimonene and phosphorene have fascinated emergent attention. Motivated by this, first principles calculations have been employed to investigate electronic, vibrational and optical properties of blue phosphorene (BP). Unlike graphene and black phosphorene, blue phosphorene demonstrates a wide fundamental indirect band gap of 2.07 eV between M to K point. The phonon dispersion curve shows dynamical stability of the monolayer. We have also calculated optical properties of blue phosphorene. Our observations suggest that absorption process begins in visible (VIS) region, but peaks in ultraviolet (UV) region at the energy range of 7.39–9.33 eV. The maximum reflectivity arises up to 35% at 9.57 eV. The outcome concludes that blue phosphorene is a prominent material for optoelectronic applications.

Prediction of ϕ-P and σ-P: Two New Strain-Interconvertible Phosphorene Allotropes

In this study, we propose two new 2D phosphorene allotropes, ϕ-P and σ-P, and use density functional theory calculations to explore their structural, electronic, and mechanical properties. The atom...

Novel green phosphorene sheets to detect tear gas molecules - A DFT insight

The green phosphorene (GP) nanosheet, one of the allotropes of layered phosphorene is employed to detect the existence of tear gas molecules. The tear gas molecules such as 1-bromo-2-butanone, bromoacetone, and bromobenzyl cyanide are examined with the service of the ATK-VNL package by employing density functional theory (DFT) method. The geometrical stability of the chief component is affirmed with the support of formation energy and electronic fingerprints of GP nanosheet like electron density, band structure, and projected density of states (PDOS) spectrum are estimated. In this research work, using DFT technique, for the first time, surface adsorption characteristics of the target molecules on GP nanosheet are explored with the assistance of adsorption energy, average energy gap variation, and Bader charge transfer, which further suggest the deployment of GP in sensing the presence of tear gas molecules.

Hierarchically Structured Allotropes of Phosphorus from Data‐Driven Exploration

AbstractThe discovery of materials is increasingly guided by quantum‐mechanical crystal‐structure prediction, but the structural complexity in bulk and nanoscale materials remains a bottleneck. Here we demonstrate how data‐driven approaches can vastly accelerate the search for complex structures, combining a machine‐learning (ML) model for the potential‐energy surface with efficient, fragment‐based searching. We use the characteristic building units observed in Hittorf's and fibrous phosphorus to seed stochastic (“random”) structure searches over hundreds of thousands of runs. Our study identifies a family of hierarchically structured allotropes based on a P8 cage as principal building unit, including one‐dimensional (1D) single and double helix structures, nanowires, and two‐dimensional (2D) phosphorene allotropes with square‐lattice and kagome topologies. These findings yield new insight into the intriguingly diverse structural chemistry of phosphorus, and they provide an example for how ML methods may, in the long run, be expected to accelerate the discovery of hierarchical nanostructures.

Long Radiation Lifetime and Quasi-Isotropic Excitons in Antioxidant V–V Binary Phosphorene Allotropes with Intrinsic Dipole

Two-dimensional (2D) V–V binary materials are gaining extensive attention because of high carrier mobility, largely tunable optical exciton properties, and high sensitivity to optical excitation. H...

Inorganic gas sensing of green phosphorene nanosheet: insights from density functional theory

Our work highlights the functionality of a novel two-dimensional phosphorene allotrope entitled green phosphorene for inorganic gas detection for the first time. Four inorganic molecules, NH3, SO2, HCN and O3, are considered as adsorbates and the adsorption conformation, adsorption energy, charge transfer, density of states, and electronic band structure are systematically scrutinized based on density functional theory. Our calculations show that the adsorption energy of O3 on pristine green phosphorene is the lowest among the four considered gas molecules, suggesting that the substrate is more sensitive to O3. Significant changes in electronic structures confirm the possibility of green phosphorene for O3 detection. Biaxial strains and electric fields were applied to investigate the changes in adsorption behavior. The presence of compressive strain could enhance adsorption sensitivity between O3 and green phosphorene, while the tensile strain induces the dissociative adsorption that not suitable for reversible sensor. Furthermore, by controlling the orientation of external electric field, it is possible to achieve O3 adsorption-desorption cycle, which is of great significance for green phosphorene in the application of reversible gas sensor.

Novel phosphorus-based 2D allotropes with ultra-high mobility

Electronic structure calculations based on density functional theory were performed to investigate structural, mechanical, and electronic properties of phosphorene-based large honeycomb dumbbell (LHD) hybrid structures and a new phosphorene allotrope, referred to as ψ″-P. The LHD hybrids (i.e., X6P4; X being C or Si or Ge or Sn) and ψ″-P have significantly higher bandgaps than the corresponding pristine LHD structures, except the case of C6P4, which is metallic. ψ″-P is found to be a highly flexible p-type material which shows strain-engineered photocatalytic activity in a highly alkaline medium. The carrier mobility of the considered systems is as high as 105 cm2 V−1 s−1 (specifically the electron mobility of LHD structures). The calculated STM images display the surface morphologies of the LHD hybrids and ψ″-P. The predicted phosphorus-based 2D structures with novel electronic properties may be candidate materials for nanoscale devices.

Temperature-dependent mechanical properties of black and blue phosphorene by molecular dynamics simulations

We have studied the mechanical properties of black phosphorene (black P) and blue phosphorene (blue P) at different temperatures using molecular dynamic simulations. It is obviously found that the blue P has isotropic mechanical properties, comparing with the anisotropy of black P. This different properties between the two phosphorene allotropes results from their different structures. The calculation has demonstrated temperature has weak effect on the Young’s moduli of black and blue P. In contrast, for the black and blue P, the values of fracture stress decrease linearly as the temperature increases. On the whole, the reduction of the fracture strain is rapid at lower temperature region. Our simulation results are in qualitative agreement with the previous theoretical calculations.

New Phosphorene by Phase Combination with Tunable Electronic and Mechanical Properties

A series of new phosphorene allotropes, αβ-P, βγ-P, γδ-P, αγ-P, αδ-P, and βδ-P, produced via phase combination of four basic phosphorenes α-P, β-P, γ-P, and δ-P, are predicted using first-principles calculations. Their thermodynamic stabilities are confirmed by cohesive energy calculations. Their band alignments compared with the O2/O2– redox potential suggest an improved chemical stability toward oxidative degradation in ambient conditions. These new mixed-phase phosphorene allotropes show attractive anisotropric electronic and mechanical properties. In particular, γδ-P shows the narrowest band gap (0.80 eV based on HSE06 calculations) and the highest negative Poisson ratio among all mixed and basic phosphorenes reported to date. The γδ-P allotrope additionally exhibits tunable electronic properties and a semiconductor-to-metal transition that can be induced via uniaxial strain.

First-principles prediction of two atomic-thin phosphorene allotropes with potentials for sun-light-driven water splitting

Based on first-principles, the structures, stabilities, electronic and optical properties of two new atomic-thin phosphorene allotropes, named as stair-P and zipper-P, are systematically investigated. Stair-P and zipper-P are constructed based on the previously proposed stair-graphane and zipper-graphane, respectively. They are confirmed to be dynamically stable phosphorene allotropes with energetic stabilities comparable to the experimentally synthesized black-P and blue-P. Stair-P and zipper-P are all semiconductors with indirect band gaps of 2.32 eV and 2.00 eV, respectively. These band gaps can be effectively modulated by in-layer compressive and stretching strains. The band edges of stair-P and zipper-P are proper for water splitting at both acidic (PH = 0) and neutral (PH = 7) environments and their sun-light adsorbing abilities are better than black-P and blue-P in the visible range.