Monolayer Black Phosphorus Research Articles

Black phosphorus terahertz sensing based on photonic spin Hall effect.

A novel terahertz (THz) sensing scheme is proposed based on the photonic spin Hall effect (PSHE). By illumining a paraxial Gaussian THz beam onto a black phosphorus (BP)-based Tamm structure, the reflected beam will undergo in-plane spin splitting, i.e., the centroids of two opposite spin components separate spatially. Due to Tamm plasmon resonance, one of the spin components is very sensitive to the refractive index changes of the analyte layer sandwiched by monolayer BP and distributed Bragg reflector. The sensitivity of the spin-dependent shift can be up to 2804 mm/RIU with a refractive index resolution of ∼10-8 RIU. The sensitivity and dynamic sensing region can be flexibly tuned by the BP rotation angle, thickness of analyte layer, or operation frequency. Therefore, the proposed PSHE-based THz sensing provides a new avenue for the development of high-performance THz sensors; thus, we may find applications in chemical sensing and biosensing.

Rabi splitting obtained in a monolayer BP-plasmonic heterostructure at room temperature

Hybrid exciton states can be formed under the strong coupling of plasmons excited by metal nanostructures and excitons. Because of the large exciton binding energy, black phosphorus (BP) is an ideal platform to investigate the strong coupling. In this paper, we first demonstrate the strong coupling between local surface plasmon modes of different metal nanostructures and excitons in monolayer BP by adjusting the dimensions of nanostructures and polarization angle at room temperature. Moreover, the exciton dispersion curves obtained from the coupled oscillator model show the anti-crossing behavior at the exciton energy. And the Rabi splitting energies of the two different BP-metal nanostructures heterostructure are 250 meV and 202 meV, respectively, which paves a way towards the development of BP photodetectors, sensors, and emitters.

Influence of NiO decoration on adsorption capabilities of black phosphorus monolayer toward nitrogen dioxide: periodic DFT calculations

ABSTRACT This paper deals with the influence of NiO decoration of black phosphorene (BP) monolayer with respect to nitrogen dioxide (NO2) capture and monitoring. The most stable configuration in the adsorption adduct with the modified surface (NP) was slightly different with a shorter equilibrium distance. The modification was found to be highly favourable (−112.60 kcal/mol at HSE06/TZVP). The detection efficiency, defined here as the work function sensitivity, was enhanced by 60% after the NiO modification. While the decorated slab was a disposable sensor at room temperature, it could be an excellent reusable sensor at high temperatures (above 673 K). Moreover, the NP material displayed stronger adsorption (by a factor of 116) compared to the pristine surface, thus making the modified material an excellent candidate for NO2 capture and catalysis. The observed behaviours were discussed in terms of the electronic properties, reactivity indicators, orbital distributions, charge density difference, and density of states.

Insight into the overpotentials of electrocatalytic hydrogen evolution on black phosphorus decorated with metal clusters

Although the electrocatalytic hydrogen evolution reaction (HER) has great potential in energy conversion, the efficiency is limited by the reaction overpotential. Herein, the origin of thermodynamic overpotential in HER is studied systemically based on the proton-coupled electron transfer (PCET) theory. Metal clusters with different elements or sizes are combined with monolayer black phosphorus (BP@Mn) as model catalysts. The thermodynamic overpotentials in HER on BP@Mn originate from mainly electron transfer or concerted proton and electron transfer, which also constitutes the rate determining step. The redox potential of the rate determining step determines the efficiency of HER rather than the adsorption energy of H atoms, which also scales linearly with the LUMO state of the catalysts. In subsequent experiments, the turnover frequencies are observed to be in line with the activity trends derived theoretically. Among the different models, BP@Con exhibits the highest activity and smaller cluster exhibits higher catalytic ability. The results provide insights into the origin of thermodynamic overpotentials in HER and valuable guidance pertaining to the design of highly efficient electrocatalysts.

Unzipping of black phosphorus to form zigzag-phosphorene nanobelts

Phosphorene, monolayer or few-layer black phosphorus, exhibits fascinating anisotropic properties and shows interesting semiconducting behavior. The synthesis of phosphorene nanosheets is still a hot topic, including the shaping of its two-dimensional structure into nanoribbons or nanobelts. Here we report electrochemical unzipping of single crystalline black phosphorus into zigzag-phosphorene nanobelts, as well as nanosheets and quantum dots, via an oxygen-driven mechanism. The experimental results agree well with our theoretical calculations. The calculation for the unzipping mechanism study suggests that interstitial oxygen-pairs are the critical intermediate species for generating zigzag-phosphorene nanobelts. Although phosphorene oxidation has been reported, lengthwise cutting is hitherto unreported. Our discovery of phosphorene cut upon oxidation represents a previously unknown mechanism for the formation of various dimensions of phosphorene nanostructures, especially zigzag-phosphorene nanobelts. It opens up a way for studying the quantum effects and electronic properties of zigzag-phosphorene nanobelts.

First-principles study of a substitutionally doped phosphorene as anode material for Na-ion batteries

An effective strategy to design high-performance anode materials is a significant task for rechargeable batteries technologies. Recently, sodium-ion batteries have attracted extensive attention because can be considered as an alternative for lithium-ion batteries in large-scale renewable energy storage applications due to abundant sodium resources and similar electrochemical mechanisms. In this paper, the first-principles density-functional theory calculations have been carried out to estimate the potential prospects of substitutionally doped monolayer of black phosphorus (BP) as an anode material for Na-ion batteries. It was found that the BP monolayer has negative binding energies for Sc, Co, Cu, B, F, and Cl dopants. Moreover, it was also shown that after sodium adsorbing, F and Cl atoms diffuse from phosphorene lattice on the surface of Na, which eliminates these materials from application in energy storage systems. Given these advantages, it is expected that Sc-, Co-, Cu- and B-doped phosphorus monolayers are promising anode materials for Na-ion batteries, with a maximum value of specific capacity of 438.6 mAh/g for B-doped system.

A novel two-dimensional sp-sp2-sp3 hybridized carbon nanostructure with a negative in-plane Poisson ratio and high electron mobility

A novel two-dimensional (2D) semiconducting carbon allotrope is proposed by inserting alkyne into tetrahexcarbon. This new carbon allotrope consists of tetra-rings and acetylenic linkages and is called TAL-carbon. To the best of our knowledge, this is the first 2D carbon allotrope composed of sp-sp2-sp3 hybridized carbon atoms. Due to its unique puckered structure, TAL-carbon is the fourth 2D carbon material with an intrinsic in-plane negative Poisson ratio (NPR) reported after graphene, penta-graphene, and tetrahexcarbon. Materials with NPR exhibit a wide range of potential applications in biomedicine, aerospace industries, and precision instruments. TAL-carbon has an indirect band gap of 1.614 eV. At room temperature, it exhibits high in-plane electron mobility of up to ~3.5 × 104 cm2V−1s−1, which is 30 times higher than monolayer black phosphorus and two orders of magnitude higher than monolayer MoS2. The phonon dispersion curves and in-plane elastic constants indicate that TAL-carbon is dynamically and mechanically stable. Its equibiaxial strain limit reaches 13.7%, similar to that of graphene. An ab initio molecular dynamics (AIMD) simulation demonstrates that TAL-carbon is thermally stable at 300 K and 1000 K. The results show that TAL-carbon is a promising 2D auxetic material for applications in nanomechanics and nanoelectronics.

Probing the anisotropy of Landau levels in phosphorene by magneto-capacitance with a parabolic potential confinement

We theoretically investigate the Landau levels (LLs) and magneto-capacitance (MC) of monolayer black phosphorus under a perpendicular magnetic field, on which a parabolic potential is applied along with the armchair and zigzag directions, respectively. By both analytically perturbative calculation and numerical diagonalization based on an effective k ⋅ p Hamiltonian, we find that the LLs parabolically depend on the wave vectors and show strong anisotropy as the parabolic potential is applied along with different crystal directions. Specifically, the analytical LLs obtained by perturbative calculation from a decoupled single-band Hamiltonian are in good agreement with the numerical results. Importantly, the LLs are no longer linearly dependent on the magnetic field and level index even in the low energy regime due to the confinement of parabolic potential which repaints the cyclotron orbits. Moreover, the MC spectrum clearly reflects the structure of the LLs and exhibits strong anisotropic oscillating patterns. It can be used to determine the band parameters of phosphorene, i.e., the effective masses and inter-band coupling in the absence of magnetic and electric fields.

Transition metal (TM = Cr, Mn, Fe, Co, Ni) doped phosphorene as anode material for lithium-ion batteries predicted from first-principle calculations

With the advancements of portable electronic hardware, the capacity and rate performance of conventional battery materials cannot satisfy the needs. Thus the search for new anode materials has recently become an upcoming research area. Monolayer blackphosphorus (BP), a newly created material, can turn out to be the next generation commercial anode material since it has a very low diffusion barrier (0.08 eV). However, its storage capacity is not large enough (432.79 mAh g−1). To improve its storage performance, in this work, we study the properties of transition metal (TM = Cr, Mn, Fe, Co, Ni) controlled BP (TMBP) to be used as the negative cathode material. We use the density functional theory calculations for the work. The doping impact is explained by the electronic structure and the Mulliken population analysis. We show that doping BP with Fe is a viable method to get high capacity and high diffusion rate anode materials. Our results show that the transition metals can increase the binding energy between TMBP and lithium, and hence the storage capacity. The lithium storage capacity of Fe-doped BP is found to be more than 800 mAh g−1 along with a low diffusion barrier (0.09 eV). Additionally, we examined the effects of doping on magnetism. Interestingly, it is observed that the magnetism of TM-doped BP varies during lithium insertion.

Disorder effect on mass-asymmetry in monolayer black phosphorus

In this work, we calculated the band structure for the monolayer black phosphorus (phosphorene) from the slater-Koster tight-binding method, where the effect of s-p mixing is considered. Using the new parameters, we studied the electronic properties of phosphorene. The electronic properties were calculated using the recursive Green’s Function method. From the resistance calculation, we showed that electrons in the ZZ directions had an effective mass ten times larger than those in the AC direction, which agrees with experimental results. We investigated the effect of disorder on the anisotropy of the effective mass and we showed that the intrinsic anisotropy is robust to the presence of disorder.

Tunable plasmon-induced transparency based on monolayer black phosphorus by bright-dark mode coupling

We theoretically propose a compound metasurface structure consisting of a patterned black phosphorus (BP) sheet sandwiched by dielectrics, which can achieve a tunable plasmon-induced transparency (PIT) effect in the mid-infrared region. The PIT effect can be actively adjusted by changing the geometric parameters and the carrier concentration of BP. The mechanism of PIT originates from the near-field coupling between the bright mode and the dark mode. The numerical simulation results are highly consistent with the theoretical calculations of the coupled Lorentz oscillator model. In addition, our proposed structure system exhibits a strong dispersion accompanied with a group index of ∼15, which provides a new strategy for slow light devices.

Assessment of the vibrational resonant frequency of anisotropic black phosphorus nanoribbon

Black phosphorus (BP) has been enjoying popularity in mechanical and optoelectronic devices due to its superior anisotropic puckered structure. However, the vibrational properties of BP remain unexplored which greatly limits its wide applications in resonance-based nano electromechanical system (NEMS) devices. Therefore, in order to design mechanically reliable ultra-sensitive nanosensors, molecular dynamics simulations are utilized to explore the vibrational properties of monolayer BP. We have systematically assessed the effects of the initial actuation amplitude, internal vacancy density and mechanical strain on the vibrational properties of monolayer BP along the armchair and zigzag directions. It is found that the pristine monolayer BP exhibits lower energy disspation and smaller dominant resonant frequency during free vibration along the armchair direction than along the zigzag direction, indicating the anisotropic mechanical vibrational properties of monolayer BP, which further result in anisotropic multimode resonant characteristics in the vibration frequency spectrum. Additionally, the dominant frequency monotonically decreases gradually with increment of the internal vacancy density, while increasing with increment of the initial actuation amplitude and the mechanical strain. The energy dissipation increases gradually with increment of the initial actuation amplitude and internal vacancy density, but decreases under mechanical strain. Overall, these findings provide a fundamental understanding of the resonant properties of monolayer anisotropic BP that sheds light on its applications in micro- or nano-resonator-based devices.

Observation of excitonic series in monolayer and few-layer black phosphorus

We report the full sequence of excitonic states in monolayer and few-layer black phosphorus (BP). High-quality BP samples are acquired by treating the silicon oxide substrate with a self-assembled monolayer hydrophobic molecule, which facilitates the access to their ground and higher-lying states of intrinsic excitons through the reflection and photoluminescence excitation spectra. Combined with first-principles and model calculations, we further determine that the exciton binding energy shrinks by \ensuremath{\sim}6-fold from 940 meV in monolayer to 160 meV in bilayer BP, yet it only decreases slightly to 108 meV in trilayer. This could be attributed to the strong interlayer coupling and lattice shrinking in multilayer BP samples. Our results shed light on the unique excitonic optical properties of two-dimensional BP.

Tunable Anisotropic Perfect Enhancement Absorption in Black Phosphorus-Based Metasurfaces

In this work, we theoretically propose an anisotropic metasurface absorber, unit cell of which consists of a continuous monolayer black phosphorus (BP) sheet, sandwiched between a circular silver ring and a dielectric layer stacking on a silver substrate. Numerical results reveal that perfect enhancement absorption can be achieved in both armchair and zigzag directions, in which the resonant absorption peaks occur at different wavelengths due to the anisotropic property of BP. The calculated results by finite-difference time domain (FDTD) simulations have a good agreement with the coupled-mode theory. The physical mechanism of the perfect absorption is attributable to the critical coupling effect. Furthermore, the anisotropic perfect absorber not only exhibits tunable characteristics by varying the electron doping concentration, but also shows a wide-angle tolerance. In addition, our proposed absorber can achieve an arbitrary number of absorption bands by setting a suitable thickness of the dielectric layer. These results may have great potential applications in spectral imaging and photodetectors in the mid-infrared region.

First principle study on interfacial interaction of black phosphorus and CsBr vdW heterostructure

Two dimensional crystalline materials have attracted much attentions due to the establishment of heterostructure that can adjust their electrical and optical properties, and have potential applications in lasers, light-emitting diodes, solar cells and high mobility transistors. And the interface engineering is an effective route to tune structural and electrical properties in semiconductor heterostructures. In this study, the electronic structure, charge transport and optical properties of monolayer caesium bromide and black phosphorus (CsBr/BP) heterostructure are calculated by the first principle based on density functional theory (DFT). It was found that the characteristics of electronic band structures of the monolayer CsBr and BP remain in the heterostructure, and the effective mass and carrier mobility are highly anisotropic. When the heterostructure is uniaxially stretched, the mobility of electron is greater than that of the hole, while the biaxial stretching is just the opposite, the mobility of hole is greater than that of the electron. In addition, compared with the CsBr monolayer, the light absorption of the heterostructure is significantly enhanced, especially in the infrared, indicating that the CsBr/BP heterostructure can be well applied to photovoltaic devices in the future.

Selective linear etching of monolayer black phosphorus using electron beams**Project supported by the National Natural Science Foundation of China (Grant Nos. 11622437, 61674171, 11804247, and 11974422), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000), Key Research Program of Frontier Sciences, Chinese Academy of Sciences (B.L, W.Z.), the Fundamental Research Funds for the Central Universities, China,

Point and line defects are of vital importance to the physical and chemical properties of certain two-dimensional (2D) materials. Although electron beams have been demonstrated to be capable of creating single- and multi-atom defects in 2D materials, the products are often random and difficult to predict without theoretical inputs. In this study, the thermal motion of atoms and electron incident angle were additionally considered to study the vacancy evolution in a black phosphorus (BP) monolayer by using an improved first-principles molecular dynamics method. The P atoms in monolayer BP tend to be struck away one by one under an electron beam within the displacement threshold energy range of 8.55–8.79 eV, which ultimately induces the formation of a zigzag-like chain vacancy. The chain vacancy is a thermodynamically metastable state and is difficult to obtain by conventional synthesis methods because the vacancy formation energy of 0.79 eV/edge atom is higher than the typical energy in monolayer BP. Covalent-like quasi-bonds and a charge density wave are formed along the chain vacancy, exhibiting rich electronic properties. This work proposes a theoretical protocol for simulating a complete elastic collision process of electron beams with 2D layers and will facilitate the establishment of detailed theoretical guidelines for experiments on 2D material etching using focused high-energy electron beams.

Highly improved carbon dioxide sensitivity and selectivity of black phosphorene sensor by vacancy doping: A quantum chemical perspective

AbstractThe adsorption and sensing properties of a carbon dioxide (CO2) molecule on the pristine (BP) and vacancy‐doped (DP) black phosphorusmono layers have been investigated using the periodic density functional theory at Heyd‐Scuseria‐Ernzerhof (HSE06)/triple‐zeta valence polarization (TZVP). For both sensors, the most stable structures among the recognized possibilities preferred a linear configuration for carbon dioxide, with a shorter equilibrium distance (2.13 Å) on the defect‐containing surface. Although carbon dioxide was weakly physiosorbed on both phosphorene sensors (up to −2.52 kcal/mol), the defect‐engineered material presented highly improved sensitivity (by a factor of 6.6) to CO2 compared to the pristine layer. The former was also a (2.6 times) better work function sensor of carbon dioxide. At the same time, recovery was extremely fast (lasting for 70 ps at most) at room temperature. The selectivity coefficient of carbon dioxide was also strikingly high (64.0). The improved nanosensor would be a step forward in the rational design of highly sensitive and reusable detectors of carbon dioxide.

Plasma Thinning of Large Black Phosphorus Flakes

The growing interest over the 2D materials has led to the discovery of exfoliated black phosphorus (bP), a semiconductor with a thickness-dependent bandgap. The direct bandgap energy varies from 0.3 eV for bulk materials to 1.9 eV for the monolayer of black phosphorus. The fabrication of thin layers is, however, difficult because the layers photo-oxidize in air into phosphoric acid with kinetic that gets faster for thinner layers1. Inspired by a new method to produce thin layers of black phosphorus using oxygen plasma, we work to optimise the process for making large few-layers bP flakes2. Using ICP-RIE oxygen plasma, exfoliated flakes of black phosphorus were etched in a controlled way and Raman spectroscopy was used to evaluate the quality of the flakes after plasma treatments. The results show no sign of high-degradation of the bP crystal structure after the plasma treatment. Here we show that the method can be adapted to produce high quality thin flakes of black phosphorus towards incorporation into electronic and optoelectronic applications. 1 Favron, A., Gaufrès, E., Fossard, F. et al. Photooxidation and quantum confinement effects in exfoliated black phosphorus. Nature Mater 14, 826–832 (2015) 2 Pei, J., Gai, X., Yang, J. et al. Producing air-stable monolayers of phosphorene and their defect engineering. Nat Commun 7, 10450 (2016)

Phosphorene defects for high-quality detection of nitric oxide and carbon monoxide: A periodic density functional study

The electronic and sensing properties of pristine and defect-tuned black phosphorus monolayer for the monitoring of nitric oxide (NO) and carbon monoxide (CO) at two defect concentrations (0.0165 and 0.0073 Å−2) were investigated within the framework of periodic density functional theory (DFT). Several configurations with preserved integrity were found plausible for both molecules at the vacant sites in which the ones with the lowest energy favored top site adsorption. We found that the detection sensitivities of all phosphorene layers correlated well with the electrophilicity of the structures. The performance data showed that the defect-free phosphorene layer could not operate as a reliable conductance-based sensor, but could be considered a satisfactory work function sensor for the analytes at hand. On the contrary, the defect-tuned phosphorene layer would be an excellent detector for both molecules, especially providing a high sensitivity at both concentrations (up to 270.0) and excellent reusability (3.6 ms) for the NO detection without any dependence on external manipulation. Carbon monoxide was better detected (1043.3) at a lower concentration, however. Excellent selectivity was observed for both molecules in dry and humid air atmospheres. The corresponding band structures and density of states were discussed. The analysis of the localized orbital locator (LOL) contour maps indicated that the C–P and N–P bonds behaved van der Waals (vdW) and polar covalent types, respectively. Overall, this paper provides attractive data for the rational design of novel chemosensors for the noxious NO and CO molecules.

Exploiting black phosphorus based-Tamm plasmons in the terahertz region.

Polarization-sensitive Tamm plasmons are investigated in a multi-layer photonic configuration where a monolayer black phosphorus (BP) is coated on a Bragg mirror separated by a dielectric. Owing to the in-plane anisotropy of BP, the Tamm plasmon can be excited selectively by tuning the BP carrier density. Cross-polarization conversion occurs when the armchair direction of BP makes an angle with the incident plan, i.e., ϕ≠0 or 90°. The BP-based Tamm device can be used as an intensity modulator with a modulation depth up to ∼100% and an insertion loss smaller than -0.55 dB. By analyzing the polarization evolution carefully, a multichannel polarization division multiplexing scheme is proposed and discussed. These findings open a new avenue for exploiting versatile tunable THz devices based on the monolayer of BP.