Structure Of Phosphorene Research Articles

The prospects of phosphorene as an anode material for high-performance lithium-ion batteries: a fundamental study

To completely understand lithium adsorption, diffusion, and capacity on the surface of phosphorene and, therefore, the prospects of phosphorene as an anode material for high-performance lithium-ion batteries (LIBs), we carried out density-functional-theory calculations and studied the lithium adsorption energy landscape, the lithium diffusion mobility, the lithium intercalation, and the lithium capacity of phosphorene. We also carried out, for the very first time, experimental measurement of the lithium capacity of phosphorene. Our calculations show that the lithium diffusion mobility along the zigzag direction in the valley of phosphorene was about 7 to 11 orders of magnitude faster than that along the other directions, indicating its ultrafast and anisotropic diffusivity. The lithium intercalation in phosphorene was studied by considering various Li n P16 configurations (n = 1–16) including single-side and double-side adsorptions. We found that phosphorene could accommodate up to a ratio of one Li per P atom (i.e. Li16P16). In particular, we found that, even at a high Li concentration (e.g. x = 1 in Li x P), there was no lithium clustering, and the structure of phosphorene (when fractured) is reversible during lithium intercalation. The theoretical value of the lithium capacity for a monolayer phosphorene is predicted to be above 433 mAh g−1, depending on whether Li atoms are adsorbed on the single side or the double side of phosphorene. Our experimental measurement of the lithium capacity for few-layer phosphorene networks shows a reversible stable value of ∼453 mAh g−1 even after 50 cycles. Our results clearly show that phosphorene, compared to graphene and other two-dimensional materials, has great promise as a novel anode material for high-performance LIBs.

Even–odd effect on the edge states for zigzag phosphorene nanoribbons under a perpendicular electric field

We study the variation of electronic property for zigzag-edge phosphorene nanoribbons (ZPNRs) under a perpendicular electric field (PEF). Using the tight-binding Hamiltonian combined with the surface lattice Green’s function (GF) approach, we show that the response of edge states to PEF for a N-ZPNR with even- or odd-N (number of zigzag chains) is qualitatively different. The field opens a gap between two edge bands near the Fermi energy for even-N ribbons, but for odd-N ones where the two edge bands are always nearly degenerated. This difference is originally from that the Stark-effect-induced energies at the upper and lower edges for even- and odd-N ZPNRs are different due to the peculiar lattice structure of phosphorene. In consequence, the electronic densities are more localized at the edges driven by the field for even-N ZPNRs but not for odd-N ones. This even–odd effect is also reflected in conductance, which indicates that the odd-N ZPNRs may be more suitable for the usage of field-effect transistor.

Evolution of electronic structure of few-layer phosphorene from angle-resolved photoemission spectroscopy of black phosphorous

A complete set of tight-binding parameters for the description of the quasiparticle dispersion relations of black phosphorous (BP) and N-layer phosphorene with N = 1 ...∞ is presented. The parameters, which describe valence and conduction bands, are fit to angle-resolved photoemission spectroscopy (ARPES) data of pristine and lithium doped BP. We show that zone-folding of the experimental three-dimensional electronic band structure of BP is a simple and intuitive method to obtain the layer-dependent two-dimensional electronic structure of few-layer phosphorene. Zone folding yields the band gap of N-layer phosphorene in excellent quantitative agreement to experiments and ab initio calculations. A combined analysis of optical absorption and ARPES spectra of pristine and doped BP is used to estimate a value for the exciton binding energy of BP.

Spin-orbit coupling and spin relaxation in phosphorene: Intrinsic versus extrinsic effects

First-principles calculations of the essential spin-orbit and spin relaxation properties of phosphorene are performed. Intrinsic spin-orbit coupling induces spin mixing with the probability of $b^2 \approx 10^{-4}$, exhibiting a large anisotropy, following the anisotropic crystalline structure of phosphorene. For realistic values of the momentum relaxation times, the intrinsic (Elliott--Yafet) spin relaxation times are hundreds of picoseconds to nanoseconds. Applying a transverse electric field (simulating gating and substrates) generates extrinsic $C_{2v}$ symmetric spin-orbit fields in phosphorene, which activate the D'yakonov--Perel' mechanism for spin relaxation. It is shown that this extrinsic spin relaxation also has a strong anisotropy, and can dominate over the Elliott-Yafet one for strong enough electric fields. Phosphorene on substrates can thus exhibit an interesting interplay of both spin relaxation mechanisms, whose individual roles could be deciphered using our results.

Direct observation of the layer-dependent electronic structure in phosphorene

Phosphorene, a single atomic layer of black phosphorus, has recently emerged as a new two-dimensional (2D) material that holds promise for electronic and photonic technologies. Here we experimentally demonstrate that the electronic structure of few-layer phosphorene varies significantly with the number of layers, in good agreement with theoretical predictions. The interband optical transitions cover a wide, technologically important spectral range from the visible to the mid-infrared. In addition, we observe strong photoluminescence in few-layer phosphorene at energies that closely match the absorption edge, indicating that they are direct bandgap semiconductors. The strongly layer-dependent electronic structure of phosphorene, in combination with its high electrical mobility, gives it distinct advantages over other 2D materials in electronic and opto-electronic applications.

Light-Matter Interactions in Phosphorene.

Since the beginning of 2014, phosphorene, a monolayer or few-layer of black phosphorus, has been rediscovered as a two-dimensional (2D) thin film, revealing a plethora of properties different from the bulk material studied so far. Similar to graphene and transition metal dichalcogenides (TMDs), phosphorene is also a layered material that can be exfoliated to yield individual layers. It is one of the few monoelemental 2D crystals and the only one, besides graphene, known to be stable in monolayer, few layer, and bulk form. Recently the intensified research in phosphorene is motivated not only by the study of its fundamental physical properties in the 2D regime, such as tunable bandgap and anisotropic behavior, but also by the high carrier mobility and good on/off ratio of phosphorene-based device prototypes, making it a potential alternative for next generation nanooptoelectronics and nanophotonics applications in the "post-graphene age" The electronic bandgap of phosphorene changes from 0.3 eV in the bulk to 2.1 eV in monolayer. Thus, phosphorene exhibits strong light-matter interactions in the visible and infrared (IR) frequencies. In this Account, we present the progress on understanding the various interactions between light and phosphorene, giving insight into the mechanism of these interactions and the respective applications. We begin by discussing the fundamental optical properties of phosphorene, using theoretical calculations to depict the layer-dependent electronic band structures and anisotropic optical properties. Many-body effects in phosphorene, including excitons and trions and their binding energies and dynamics are reviewed as observed in experiments. For phosphorene, the fast degradation in ambient condition, caused by photoinduced oxidation, is considered as a longstanding challenge. In contrast, oxidation can be used to engineer the band structure of phosphorene and, in parallel, its optical properties. Based on the strong light-matter interactions, we introduce a controllable method to directly oxidize phosphorene by laser techniques. With the oxidization induced by laser scanning, localized bandgap engineering can be achieved and microphotonics are demonstrated on the oxidized phosphorene. Finally, we will present a brief discussion on the realization of phosphorene-based building blocks of optoelectronic devices. Naturally, the strong light-matter interactions in phosphorene could enable efficient photoelectric conversion in optoelectronic devices. We will describe high performance photodetectors based on phosphorene, and the working mechanism of those devices will be introduced. The photovoltaic effect could also be exhibited in phosphorene. This indicates the pervasive potential of phosphorene in nanooptoelectronics.

Strain-induced topological phase transition in phosphorene and in phosphorene nanoribbons

Using the tight-binding (TB) approximation with inclusion of the spin-orbit interaction, we predict a topological phase transition in the electronic band structure of phosphorene in the presence of axial strains. We derive a low-energy TB Hamiltonian that includes the spin-orbit interaction for bulk phosphorene. Applying a compressive biaxial in-plane strain and perpendicular tensile strain in ranges where the structure is still stable leads to a topological phase transition. We also examine the influence of strain on zigzag phosphorene nanoribbons (zPNRs) and the formation of the corresponding protected edge states when the system is in the topological phase. For zPNRs up to a width of 100 nm the energy gap is at least three orders of magnitude larger than the thermal energy at room temperature.

The tunable electronic structure and optic absorption properties of phosphorene by a normally applied electric field

We studied the electronic structure and optical absorption properties of phosphorene (a monolayer black phosphorus) under a normally applied electric field. The electric field enlarges the energy gap, weakens the effective mass anisotropy, and increases the effective mass component along the armchair direction (x-direction) for both conduction and valence bands but provides little change to the component along the zigzag direction (y-direction). The band edge optical absorption is completely polarized in the x-direction, and decreases when increasing the electric field. If the exciting frequency is beyond the energy gap, the absorption for the y-polarized light becomes nonzero, but the absorption is still highly polarized.

Multiple unpinned Dirac points in group-Va single-layers with phosphorene structure

AbstractEmergent Dirac fermion states underlie many intriguing properties of graphene, and the search for them constitutes one strong motivation to explore two-dimensional (2D) allotropes of other elements. Phosphorene, the ultrathin layers of black phosphorous, has been a subject of intense investigations recently, and it was found that other group-Va elements could also form 2D layers with similar puckered lattice structure. Here, by a close examination of their electronic band structure evolution, we discover two types of Dirac fermion states emerging in the low-energy spectrum. One pair of (type-I) Dirac points is sitting on high-symmetry lines, while two pairs of (type-II) Dirac points are located at generic k-points, with different anisotropic dispersions determined by the reduced symmetries at their locations. Such fully-unpinned (type-II) 2D Dirac points are discovered for the first time. In the absence of spin-orbit coupling (SOC), we find that each Dirac node is protected by the sublattice symmetry from gap opening, which is in turn ensured by any one of three point group symmetries. The SOC generally gaps the Dirac nodes, and for the type-I case, this drives the system into a quantum spin Hall insulator phase. We suggest possible ways to realise the unpinned Dirac points in strained phosphorene.

Optical reflection, transmission and absorption properties of single-layer black phosphorus from a model calculation

An effective anisotropic tight-binding model is developed to analytically describe the low-energy electronic structure and optical response of phosphorene (a black phosphorus (BP) monolayer). Within the framework of the model, we derive explicit closed-form expressions, in terms of elementary functions, for the elements of the optical conductivity tensor of phosphorene. These relations provide a convenient parametrization of the highly anisotropic optical response of phosphorene, which allows the reflectance, transmittance, and absorbance of this material to be easily calculated as a function of the frequency of the incident radiation at arbitrary angles of incidence. The results of such a calculation are presented for both a free-standing phosphorene layer and the phosphorene layer deposited on a substrate, and for the two principal cases of polarization of the incident radiation either parallel to or normal to the plane of incidence. Our findings (e.g., a ‘quasi-Brewster’ effect in the reflectance of the phosphorene/ overlayer system) pave the way for developing a new, purely optical method of distinguishing BP monolayers.

Electronic structure and optic absorption of phosphorene under strain

We studied the electronic structure and optic absorption of phosphorene (monolayer of black phosphorus) under strain. Strain was found to be a powerful tool for the band structure engineering. The in-plane strain in armchair or zigzag direction changes the effective mass components along both directions, while the vertical strain only has significant effect on the effective mass in the armchair direction. The band gap is narrowed by compressive in-plane strain and tensile vertical strain. Under certain strain configurations, the gap is closed and the energy band evolves to the semi-Dirac type: the dispersion is linear in the armchair direction and is gapless quadratic in the zigzag direction. The band-edge optic absorption is completely polarized along the armchair direction, and the polarization rate is reduced when the photon energy increases. Strain not only changes the absorption edge (the smallest photon energy for electron transition), but also the absorption polarization.

Structure, Preparation and Properties of Phosphorene

Structure, Preparation and Properties of Phosphorene

Fracture patterns and the energy release rate of phosphorene.

Phosphorene, also known as monolayer black phosphorus, has been enjoying popularity in electronic devices due to its superior electrical properties. However, it's relatively low Young's modulus, low fracture strength and susceptibility to structural failure have limited its application in mechanical devices. Therefore, in order to design more mechanically reliable devices that utilize phosphorene, it is necessary to explore the fracture patterns and energy release rate of phosphorene. In this study, molecular dynamics simulations are performed to investigate phosphorene's fracture mechanism. The results indicate that fracture under uniaxial tension along the armchair direction is attributed to a break in the interlayer bond angles, while failure in the zigzag direction is triggered by the break in both intra-layer angles and bonds. Furthermore, we developed a modified Griffith criterion to analyze the energy release rate of phosphorene and its dependence on the strain rates and orientations of cracks. Simulation results indicate that phosphorene's energy release rate remains almost unchanged in the armchair direction while it fluctuates intensively in the zigzag direction. Additionally, the strain rate was found to play a negligible role in the energy release rate. The geometrical factor α in the Griffith's criterion is almost constant when the crack orientation is smaller than 45 degree, regardless of the crack orientation and loading direction. Overall, these findings provide helpful insights into the mechanical properties and failure behavior of phosphorene.

Atomically thin binary V–V compound semiconductor: a first-principles study

Using first-principles calculations, we propose a class of unexplored binary V–V compound semiconductors with monolayer black phosphorene and blue phosphorene structures.

Spontaneous ripple formation in phosphorene: electronic properties and possible applications

According to the Mermin-Wagner theorem and theory of elasticity, long-range order in two-dimensional (2D) crystals will be inevitably destroyed due to a thermal fluctuation. Thus, a 2D lattice prefers a corrugation meaning that a 2D crystal is easy to present a ripple. In this work, we, via employing ab initio molecular dynamics (AIMD) simulations, for the first time evidenced that the inherent dynamics of phosphorene would lead to a spontaneous formation of ripples at room temperature. The height of a ripple closely associates with the temperature and the width. Via density functional theory (DFT) calculations, we further demonstrated that the emergence of ripples would remarkably reduce the bandgap of phosphorene. Via the construction of the unique phosphorene structure, we finally found that such a rippled structure is expected to be used in the light-emitting field. These results give us further knowledge of phosphorene, which goes beyond the current scope of phosphorene limited to the flat lattice.

Valence-force model and nanomechanics of single-layer phosphorene.

In order to understand the relation of strain and material properties, both a microscopic model connecting a given strain to the displacement of atoms, and a macroscopic model relating applied stress to induced strain, are required. Starting from a valence-force model for black phosphorous [Kaneta et al., Solid State Communications, 1982, 44, 613] we use recent experimental and computational results to obtain an improved set of valence-force parameters for phosphorene. From the model we calculate the phonon dispersion and the elastic properties of single-layer phosphorene. Finally, we use these results to derive a complete continuum model, including the bending rigidities, valid for long-wavelength deformations of phosphorene. This continuum model is then used to study the properties of pressurized suspended phosphorene sheets.

Tailoring magnetism of black phosphorene doped with B, C, N, O, F, S and Se atom: A DFT calculation

We calculate the electronic structure and magnetism of monolayer phosphorene doped by nonmagnetic atoms. O, S and Se impurities can induce the magnetic moment. O doping makes it become a spin-gapless semiconductor, but S and Se doping induces a half-metallic characteristic. The p orbital of dopant has a strong hybridization with P around impurities, which induces spin splitting of P and impurities. C induces a metallic character. B acts as n-type dopant and F results in p-type dopant. The magnetism of phosphorene doped by two O atoms strongly depends on the doping sites and distance between two O atoms.

Strain engineering the charged-impurity-limited carrier mobility in phosphorene

We investigate, based on the tight-binding model and in the linear deformation regime, the strain dependence of the electronic band structure of phosphorene, exposed to a uniaxial strain in one of its principle directions, the normal, the armchair and the zigzag directions. We show that the electronic band structure of strained phosphorene, for the experimentally accessible carrier densities and the uniaxial strains, is well described by a strain-dependent decoupled electron–hole Hamiltonian. Then, employing the decoupled Hamiltonian, we consider the strain dependence of the charged-impurity-limited carrier mobility in phosphorene, for both types of carriers, arbitrary carrier densities and in both armchair and zigzag directions. We show that a uniaxial tensile (compressive) strain in the normal direction enhances (weakens) the anisotropy of the carrier mobility, while a uniaxial strain in the zigzag direction acts inversely. Moreover applying a uniaxial strain in the armchair direction is shown to be ineffective on the anisotropy of the carrier mobility. These will be explained based on the effects of the strains on the carrier effective masses.

Structural phase transitions of phosphorene induced by applied strains

The effects of normal compressive strain and in-plane strain on the structures of phosphorene have been investigated by using first-principles calculations. It is quite intriguing to find that a structural transformation from pristine Z-phosphorene to a new A-phosphorene occurs under the normal compressive strain of $\ensuremath{\varepsilon}=48%$ or the anisotropic biaxial in-plane strain of ${\ensuremath{\varepsilon}}_{\mathrm{x}}=\ensuremath{-}16%$ and ${\ensuremath{\varepsilon}}_{\mathrm{y}}=54%$. In the extreme case where the pucker structure is flattened into a plane, the phosphorene structure is quite unstable at finite temperatures, transforming into another new H-phosphorene phase. The anisotropic structure of A-phosphorene gives rise to its direction-dependent mechanical properties whereas H-phosphorene exhibits isotropic mechanical properties. Both A-phosphorene and H-phosphorene are semiconductors with indirect band gaps of about 0.42 and 1.94 eV that use the Perdew-Burke-Ernzerhof exchange-correlation functional, respectively. The electronic properties of the two new phases are found to be sensitive to the magnitude and direction of the applied strains, which offer an effective method to modulate them in future device engineering.

Unique electron transport in ultrathin black phosphorene: Ab-initio study

We present first principle structural, electronic, optical and transport analysis of black phosphorene a 2D layered material. The studied configuration shows semiconducting nature and the states around the Fermi energy are mainly contributed by the p-orbitals of atoms. In optical properties, the reflective spectrum is approximately dispersed in visible range suggesting that this 2D-nanostructure can be considered as shielding for visible region. Due to the anisotropy of the electronic structure of black phosphorene, the device performance is subtaintially preferable in armchair direction. Zero-bias transmission shows no conductance channel near Fermi level but in far region prominent spectra for the same is observed for black-phospherene. The studied configurations show non-linear current–voltage (I–V) characteristics. The sensitivity for NH3 and NO2 gas molecule is explored using electronic and current–voltage (I–V) characteristics. Investigations show that the black phosphorene has strong affinity for electron seeking NO2 molecule, thus providing an opportunity for its sensor application.