Properties Of Black Phosphorus Research Articles

Theoretical Exploration of Structural and Excitonic Properties in Black Phosphorus: From First-Principles to a Semi-Empirical Approach

Theoretical Exploration of Structural and Excitonic Properties in Black Phosphorus: From First-Principles to a Semi-Empirical Approach

Recent Progress on Synthesis and Properties of Black Phosphorus and Phosphorene As New-Age Nanomaterials for Water Decontamination.

Concerted efforts have been made in recent years to find solutions to water and wastewater treatment challenges and eliminate the difficulties associated with treatment methods. Various techniques are used to ensure the recycling and reuse of water resources. Owing to their excellent chemical, physical, and biological properties, nanomaterials play an important role when integrated into water/wastewater treatment technologies. Black phosphorus (BP) is a potential nanomaterial candidate for water and wastewater treatment, especially its monolayer 2D derivative called phosphorene. Phosphorene offers relative adjustability in its direct bandgap, high charge carrier mobility, and improved in-plane anisotropy compared to the most extensively studied 2D nanomaterials. In this study, we examined the physical and chemical characteristics and synthetic processes of BP and phosphorene. We provide an overview of the latest advancements in the main applications of BP and phosphorene in water/wastewater treatment, which are categorized as photocatalytic, adsorption, and membrane filtration processes. Additionally, we explore the existing difficulties in the integration of BP and phosphorene into water/wastewater treatment technologies and prospects for future research in this field. In summary, this review highlights the ongoing necessity for significant research efforts on the integration of BP and phosphorene in water and wastewater applications.

Anisotropic magneto-optical transport properties in black phosphorus induced by in-plane magnetic field

We study the Landau levels and magneto-optical properties of bulk black phosphorus (BP) subjected to an in-plane magnetic field along the armchair direction based on an effective Hamiltonian. We analytically obtain the Landau levels by the perturbation method, which agrees well with the results of numerical diagonalization. By using the Kubo formula, we find the magneto-optical transition selection rules and conductance spectra for inter-band transitions are highly anisotropic. In particular, for linearly polarized light along the armchair direction, the magneto-optical transition selection rule is = 0, where n is the Landau level index. However, for linearly polarized light along the zigzag and stacking direction, the magneto-optical transition selection rules become = ±1. The magneto-optical conductance excited by linearly polarized light along the armchair direction is two order of magnitude larger than those excited by linearly polarized light along the zigzag and stacking direction because the inter-band coupling only exists in the armchair direction. Our results are useful to detect the band parameters of BP and design magnetically controlled optical devices based on it.

Anisotropic Raman characterization and electrical properties of black phosphorus

As a new family member of two-dimensional materials, black phosphorus has attracted much attention due to its infrared band gap and strongly anisotropic properties, bringing new concepts and applications in different fields. In characterizing black phosphorus, optical method and electrical method are typically used to obtain structural information and fundamental properties in terms of behaviors of electrons. So far, more studies are still needed to understand in depth the physical principle and facilitate applications. In this paper, multilayered black phosphorus flakes are synthesized via mechanical exfoliation from the bulk crystal, and field-effect transistors based on few-layer black phosphorus are fabricated by micro-nano fabrication technology, which owns 0°–360° four pairs of symmetrical electrodes. We experimentally obtain the characteristics of Raman modes <inline-formula><tex-math id="M1">\begin{document}${\rm{A}}_{\rm{g}}^{\rm{1}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M1.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="Z-20210129033546-1">\begin{document}$ {\rm B_{2g}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_Z-20210129033546-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_Z-20210129033546-1.png"/></alternatives></inline-formula>, and <inline-formula><tex-math id="M2">\begin{document}${\rm{A}}_{\rm{g}}^2$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M2.png"/></alternatives></inline-formula> in parallel (<i>XX</i>) and vertical (<i>XY</i>) polarization configuration. Furthermore, the angle-dependent source-drain current angle is measured through a BP field-effect transistor. The Raman spectrum results demonstrate that three characteristic peaks are located at 361, 439 and 467 cm<sup>–1</sup> in a range of 200–500 cm<sup>–1</sup>, corresponding to the vibration modes of <inline-formula><tex-math id="M3">\begin{document}${\rm{A}}_{\rm{g}}^{\rm{1}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M3.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="Z-20210129033614-1">\begin{document}$ {\rm B_{2g}}, $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_Z-20210129033614-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_Z-20210129033614-1.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M4">\begin{document}${\rm{A}}_{\rm{g}}^2$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20201271_M4.png"/></alternatives></inline-formula>, respectively. The fitting experimental data of polarization-dependent Raman spectra also show that the intensity for each of the three characteristic peaks has a 180° periodic variation in a parallel polarization configuration and also in a vertical polarization configuration. The maximum Raman intensity of A<sub>g</sub> is along the AC direction, while that of B<sub>2g</sub> is along the ZZ direction. On the other hand, the electric transport curves illustrate that the largest source leakage current can be obtained near 0° (180°) armchair direction. Such results indicate the anisotropy of black phosphorus. Furthermore, transfer curves with different electrode angles show that the weak bipolarity of black phosphorus at 45° (225°), 90° (270°), and p-type performance at 0° (180°), 135° (315°) can be offered, respectively. This work is conducive to studying the properties and practical applications of devices based on black phosphorus.

Black Phosphorus as Multifaceted Advanced Material Nanoplatforms for Potential Biomedical Applications.

Black phosphorus is one of the emerging members of two-dimensional (2D) materials which has recently entered the biomedical field. Its anisotropic properties and infrared bandgap have enabled researchers to discover its applicability in several fields including optoelectronics, 3D printing, bioimaging, and others. Characterization techniques such as Raman spectroscopy have revealed the structural information of Black phosphorus (BP) along with its fundamental properties, such as the behavior of its photons and electrons. The present review provides an overview of synthetic approaches and properties of BP, in addition to a detailed discussion about various types of surface modifications available for overcoming the stability-related drawbacks and for imparting targeting ability to synthesized nanoplatforms. The review further gives an overview of multiple characterization techniques such as spectroscopic, thermal, optical, and electron microscopic techniques for providing an insight into its fundamental properties. These characterization techniques are not only important for the analysis of the synthesized BP but also play a vital role in assessing the doping as well as the structural integrity of BP-based nanocomposites. The potential role of BP and BP-based nanocomposites for biomedical applications specifically, in the fields of drug delivery, 3D printing, and wound dressing, have been discussed in detail to provide an insight into the multifunctional role of BP-based nanoplatforms for the management of various diseases, including cancer therapy. The review further sheds light on the role of BP-based 2D platforms such as BP nanosheets along with BP-based 0D platforms—i.e., BP quantum dots in the field of therapy and bioimaging of cancer using techniques such as photoacoustic imaging and fluorescence imaging. Although the review inculcates the multimodal therapeutic as well as imaging role of BP, there is still research going on in this field which will help in the development of BP-based theranostic platforms not only for cancer therapy, but various other diseases.

Degradation of Black Phosphorus and Strategies to Enhance Its Ambient Lifetime

AbstractExfoliation of black phosphorus (BP) into phosphorene has led to the discovery of its semiconducting properties and tunable bandgap, enabling its use in a range of applications including transistors, batteries, and sensors. However, BP's ambient instability poses a considerable challenge to its incorporation into functional devices. Observed changes to the surface chemistry of BP during degradation has recently provided insight into the degradation pathways. In this review, degradation mechanisms are discussed including the effect of oxidants, such as oxygen, water, and light, on BP degradation. Additionally, a comprehensive overview on the progress made in characterizing the surface chemistry of BP is provided, as well as the methods employed to enhance its ambient stability including capping layers, covalent and noncovalent functionalization, solvent passivation, and polymer‐based protection strategies. The effect of various protection strategies on the ambient lifetime of BP and their influence on the properties of BP are discussed.

Strain-induced vibrational properties of few layer black phosphorus and MoTe2 via Raman spectroscopy

We studied and compared the effect of tensile strain on the Raman spectra of black phosphorus (BP) and molybdenum ditelluride (MoTe2) crystals by using a simple custom strain device. In-situ Raman spectroscopy on BP revealed clear red shifting of all three phonon modes, A1g, B2g and A2g, under tensile stress. From our theoretical analyses, we found that such red shifting strongly depends on the direction of the strain exerted on the system even within the elastic deformation limit (i.e. strain ≤ 1 %). In particular, calculated results for the strain along the armchair direction are consistent with our experimental data, confirming that the strain applied to the sample acts effectively along the armchair direction. In a comparative study, we found that the effect of strain on the Raman shifting is larger for BP than that for MoTe2, presumably due to the smaller Young’s modulus of BP. We also see a remarkable resemblance between donor-type intercalation induced vibrational properties and tensile stress-induced vibrational properties in BP. We anticipate that our method of in-situ Raman spectroscopy can be an effective tool that can allow observation of strain effect directly which is critical for future flexible electronic devices.

The effect of changing stacking patterns on electronic and optical properties of black phosphorus by strain:A computational study

Abstract The synergy effect on structural properties, electronic properties, and optical properties when changing strain and the number of layers at the same time of 2D black phosphorus (BP) are calculated in this paper by using first-principles calculations. The results show that with the number of the layer increased, the band-gap shows a decreasing trend, whereas the absorption edge shows a trend of red-shift. When we put different in-layer biaxial strain from −10% compressive strain (a/a0 = 90%) to 10% tensile strain (a/a0 = 110%) on all few-layer BP layers, the electronic, optical and structural properties change. In terms of electronic property, few-layer BP shows an increasing trend of the band-gap, and at the same time, a distinct change of chemical bond has been observed. As for the optical property, an anisotropic variation of the absorption and reflectivity occurs. And for the structural property, there is a noticeable regular anisotropic change of the stacking order. In our opinion, the increasing number of layers affects band splitting around the Γ point and entire BZ, which leads to the decrease of the gap. The changing of the layer from 5 L to 1L and the strain from −10% compressive strain to 10% tensile strain affect the stacking order and the change of near-band-states of few-layer BP, which further impacts the band-gap, chemical bond and its transition from metal to semiconductor of BP. Besides, the strain effect leads to the anisotropic change of the structure, which further results in the anisotropic change in the optical properties of the few-layer BP. This study implies that we can alter the function of the few-layer material by setting up the suitable strain and the number of the layer in the future.

Anisotropic thermal conductivity in direction-specific black phosphorus nanoflakes

Abstract

Anisotropic Electron-Phonon Interactions in Angle-Resolved Raman Study of Strained Black Phosphorus.

Few-layer black phosphorus (BP) with an in-plane puckered crystalline structure has attracted intense interest for strain engineering due to both its significant anisotropy in mechanical and electrical properties and its high intrinsic strain limit. Here, we investigated the phonon response of few layer BP under uniaxial tensile strain (∼7%) with in situ polarized Raman spectroscopy. Together with the first-principles density functional theory (DFT) analysis, the anisotropic Poisson's ratio in few-layer BP was verified as one of the primary factors that caused the large discrepancy in the trend of reported Raman frequency shift for strained BP, armchair (AC) direction in particular. By carefully including and excluding the anisotropic Poisson's ratio in the DFT emulations, we rebuilt both trends reported for Raman mode shifts. Furthermore, the angle-resolved Raman spectroscopy was conducted in situ under tensile strain for systematic investigation of the in-plane anisotropy of BP phonon response. The experimentally observed thickness and crystallographic orientation dependence is elaborated using DFT theory as having a strong correlation between the strain-perturbated electronic-band structure and the phonon vibration modes. This study provides insight, both experimentally and theoretically, for the complex electron-phonon interaction behavior in strained BP, which enables diverse possibilities for the strain engineering of electrical and optical properties in BP and similar two-dimensional nanomaterials.

Size-dependent interface thermal conductance in black phosphorus/SiO2 heterojunctions

Understanding the interface effect on the thermal transport properties in black phosphorus (BP)/SiO2 heterojunctions is of funcamental importance for developing BP-based nanoelectronic devices. Here, we present a bond relaxation method to illustrate an atomic-level insight into the size-dependent interface thermal transport properties of BP/SiO2 heterojunctions. It has been found that the decrease of BP membrane thickness could enhance interface adhesion energy as well as interface coupling strength in BP/SiO2 heterojunctions, which leads to an enhanced interface thermal conductance. The theoretical predictions provide a possible method on interface thermal transport properties of BP-based heterostructures for potential applications.

Linear scanning tunneling spectroscopy over a large energy range in black phosphorus

We reveal the unique electronic characteristics of the conduction band (CB) of black phosphorus (BP) by combining low-temperature scanning tunneling microscopy/spectroscopy (STM/STS), density functional theory calculations, analytic fitting, and model simulations. We discover that the differential conductance spectrum, which represents the local density of states (LDOS) of BP, exhibits a linear character over a large energy range in the unoccupied electronic state region. Combining theoretical calculations, we demonstrate that the linear character right above the conduction band minimum originates from a specific combination of the anisotropic band dispersions of BP's CB. In particular, the wave function of BP's CB possesses a pronounced density between BP layers and extends into the vacuum significantly, which is in sharp contrast to those of adjacent bands. This makes the CB dominate STS signals even when the energy is sufficiently high to involve other bands, and maintains the linearity of the STS spectrum over a wide energy range. The fact that the CB provides linear DOS and possesses pronounced wave function density in BP interlayers provides new insights for engineering the electronic structures and properties of BP and BP based materials.

Controlled p-doping of black phosphorus by integration of MoS2 nanoparticles

Black phosphorus (BP), a new family of two dimensional (2D) layered materials, is an attractive material for future electronic, photonic and chemical sensing devices, thanks to its high carrier density and a direct bandgap of 0.3–2.0 eV, depending on the number of layers. Controllability over the properties of BP by electrical or chemical modulations is one of the critical requirements for future various device applications. Herein, we report a new doping method of BP by integration of density-controlled monolayer MoS2 nanoparticles (NPs). MoS2 NPs with different density were synthesized by chemical vapor deposition (CVD) and transferred onto a few-layer BP channel, which induced a p-doping effect. Scanning electron microscopy (SEM) confirmed the size and distribution of MoS2 NPs with different density. Raman and X-ray photoelectron spectroscopy (XPS) were measured to confirm the oxidation on the edge of MoS2 NPs and a doping effect of MoS2 NPs on a BP channel. The doping mechanism was explained by a charge transfer by work function differences between BP and MoS2 NPs, which was confirmed by Kelvin probe force microscopy (KPFM) and electrical measurements. The hole concentration of BP was controlled with different densities of MoS2 NPs in a range of 1012–1013 cm−2.

Strain Effects on Properties of Phosphorene and Phosphorene Nanoribbons: a DFT and Tight Binding Study**Supported by the National Natural Science Foundation of China under Grant Nos 51572219 and 11447030, the Natural Science Foundation of Shaanxi Province of China under Grant Nos 2014JM2-1008 and 2015JM1018, and the State Key Laboratory of Transient Optics and Photonics Technology 2015 Annual Open Fund under

We perform comprehensive density functional theory calculations of strain effect on electronic structure of black phosphorus (BP) and on BP nanoribbons. Both uniaxial and biaxial strain are applied, and the dramatic change of BP’s band structure is observed. Under 0–8% uniaxial strain, the band gap can be modulated in the range of 0.55–1.06 eV, and a direct–indirect band gap transition causes strain over 4% in the y direction. Under 0–8% biaxial strain, the band gap can be modulated in the range of 0.35–1.09 eV, and the band gap maintains directly. Applying strain to BP nanoribbon, the band gap value reduces or enlarges markedly either zigzag nanoribbon or armchair nanoribbon. Analyzing the orbital composition and using a tight-binding model we ascribe this band gap behavior to the competition between effects of different bond lengths on band gap. These results would enhance our understanding on strain effects on properties of BP and phosphorene nanoribbon.

基于黑磷荧光淬灭特性的肿瘤细胞探测

基于黑磷荧光淬灭特性的肿瘤细胞探测

Air stable black phosphorous in polyaniline-based nanocomposite

The greatest challenge regarding black phosphorus (BP) comes as a result of its fast degradation when exposed to ambient conditions, which has overshadowed its applications. Herein, we report a simple and efficient route towards overcoming BP deterioration by preparing a nanocomposite with the conducting polymer polyaniline (PANI). The liquid/liquid interfacial method was employed to produce transparent, freestanding and transferable thin film of BP covered by PANI, with high stability under ambient atmosphere, up to 60 days. Otherwise, the uncapped exfoliated neat BP degraded in solely 3 days under the same conditions. Characterization data show that PANI covers efficiently the BP flakes, indicating favorable interactions between the components. The results presented here can be considered a breakthrough for employing BP as thin film in different technological applications, considering the properties of BP itself or taking advantage of synergistically combining the properties of both components.

Observation of A Raman mode splitting in few layer black phosphorus encapsulated with hexagonal boron nitride.

We investigate the impact of encapsulation with hexagonal boron nitride (h-BN) on the Raman spectrum of few layer black phosphorus. The encapsulation results in a significant reduction of the line width of the Raman modes of black phosphorus, due to a reduced phonon scattering rate. We observe a so far elusive peak in the Raman spectra ∼4 cm-1 above the A mode in trilayer and thicker flakes, which had not been observed experimentally. The newly observed mode originates from the strong black phosphorus inter-layer interaction, which induces a hardening of the surface atom vibration with respect to the corresponding modes of the inner layers. The observation of this mode suggests a significant impact of h-BN encapsulation on the properties of black phosphorus and can serve as an indicator of the quality of its surface.

Probing phonon and electrical anisotropy in black phosphorus for device alignment

Black phosphorus has emerged as a promising two-dimensional semiconductor, which has a unique structure that is anisotropic in-plane. This structural anisotropy translates to some very interesting orientation dependent properties. In this paper we present directional characterization and analysis of the phonon and electrical properties in black phosphorus. Using polarization dependent Raman we show a simple method for estimating orientation. A complementary radially contacted field effect transistor (FET) was fabricated in order to measure orientation dependent electrical properties. Mobility and transconductance followed a sinusoidal like dependence on orientation with a 30% anisotropy. Correlating these results with Raman, we show how Raman methods might be used as a nondestructive technique to orient black phosphorus devices.

Strong Modulation of Optical Properties in Black Phosphorus through Strain-Engineered Rippling.

Controlling the bandgap through local-strain engineering is an exciting avenue for tailoring optoelectronic materials. Two-dimensional crystals are particularly suited for this purpose because they can withstand unprecedented nonhomogeneous deformations before rupture; one can literally bend them and fold them up almost like a piece of paper. Here, we study multilayer black phosphorus sheets subjected to periodic stress to modulate their optoelectronic properties. We find a remarkable shift of the optical absorption band-edge of up to ∼0.7 eV between the regions under tensile and compressive stress, greatly exceeding the strain tunability reported for transition metal dichalcogenides. This observation is supported by theoretical models that also predict that this periodic stress modulation can yield to quantum confinement of carriers at low temperatures. The possibility of generating large strain-induced variations in the local density of charge carriers opens the door for a variety of applications including photovoltaics, quantum optics, and two-dimensional optoelectronic devices.

Ambipolar insulator-to-metal transition in black phosphorus by ionic-liquid gating.

We report ambipolar transport properties in black phosphorus using an electric-double-layer transistor configuration. The transfer curve clearly exhibits ambipolar transistor behavior with an ON-OFF ratio of ∼5 × 10(3). The band gap was determined as ≅0.35 eV from the transfer curve, and Hall-effect measurements revealed that the hole mobility was ∼190 cm(2)/(V s) at 170 K, which is 1 order of magnitude larger than the electron mobility. By inducing an ultrahigh carrier density of ∼10(14) cm(-2), an electric-field-induced transition from the insulating state to the metallic state was realized, due to both electron and hole doping. Our results suggest that black phosphorus will be a good candidate for the fabrication of functional devices, such as lateral p-n junctions and tunnel diodes, due to the intrinsic narrow band gap.