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Isotropic charge screening of anisotropic black phosphorus revealed by potassium adatoms
摘要： Black phosphorus has attracted great research interest due to its numerous applications in electronic devices, optoelectronic devices, energy storage, and so on. Compared with the majority of two-dimensional materials, black phosphorus possesses a unique property—its strong in-plane anisotropy. All the properties reported so far, including its effective mass, electron mobility, light absorption, thermal conductivity, and so on, have shown great anisotropy in the basal plane. This property renders black phosphorus applications not achievable with other two-dimensional materials. In this work, however, we discover a remarkable isotropic behavior in the strongly anisotropic black phosphorus—its electrostatic screening of point charges. We use the tip-induced band bending of a scanning tunneling microscope to map out the Coulomb ?eld of ionized potassium adatoms on black phosphorus and reveal its isotropic charge screening. This discovery is important for understanding electron scattering and transport in black phosphorus.
关键词： electron scattering,black phosphorus,isotropic charge screening,potassium adatoms,scanning tunneling microscope
更新于2025-09-11 14:15:04
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Ultra-Broadband, High Speed, and High-Quantum-Efficiency Photodetectors Based on Black Phosphorus
摘要： Black phosphorus (BP), a narrow band gap semiconductor without out-of-plane dangling bonds, has shown promise for broadband and integrable photodetector applications. Simultaneously exhibiting high speed and high-efficiency operation, however, remains a critical challenge for current BP-based photodetectors. Here, we demonstrate a photodetector based on the BP-based van der Waals heterostructures. The developed photodetector enables broadband responses in the visible to mid-infrared range with external quantum efficiency (EQE) ranging from 20% to 52% at room temperature. These results together with noise measurements indicate the photodetector can detect light in the pico-watt range. Furthermore, the demonstrated BP detector has ultrafast rise (1.8 ns) and fall (1.68 ns) times, and its photoresponse exhibits reproducible switching behavior even under consecutive and rapid light intensity modulations (2100 cycles, 200 MHz), as indicated by the eye-diagram measurement. By leveraging these features, we show our BP heterostructures can be configured as a point-like detector in a scanning confocal microscopy, useful for mid-infrared imaging applications.
关键词： van der Waals heterostructures,mid-infrared imaging,Black phosphorus,high speed,broadband photoresponses,photodetector
更新于2025-09-11 14:15:04
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Nonlinear vibrations of circular single-layer black phosphorus resonators
摘要： A strong nonlinear relationship between the displacement and the load in single-layer black phosphorus sheets (SLBPs) was observed under the large deflection by nanoindentation experiments. However, is rarely considered in the Nano-Electro-Mechanical-System (NEMS) resonators based on the SLBPs. In this letter, nonlinear static and dynamics behaviors of circular SLBPs (CSLBPs) are investigated using molecular dynamics (MD) simulations and a nonlinear orthotropic plate model (NOPM), respectively, where the geometrical nonlinearity is systematically considered in the NOPM. Our results show that the response-frequency curves of forced vibrations in CSLBPs meet clear hardening-type nonlinearity. The damping ratios of CSLBPs are proportional to the square of the vibration amplitude. In particular, the NOPM together with the law of energy equipartition is further utilized to study the nonlinear thermal vibrations of the CSLBPs. Checking against present MD calculations shows that the solution of the present NOPM has high accuracy. The present study should be of great help for designing NEMS resonators based on two-dimensional (2D) orthotropic materials.
关键词： nonlinear orthotropic plate model,black phosphorus,nonlinear vibrations,molecular dynamics,resonators
更新于2025-09-11 14:15:04
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pH-Dependent Degradation of Layered Black Phosphorus: Essential Role of Hydroxide Ions
摘要： The practical application of layered black phosphorus (LBP) was challenged by fast decomposition in the presence of H2O and/or O2, and the role of H2O was highly controversial. Herein, we proposed a hydroxide ion (OH-)-initiated degradation mechanism for LBP to elucidate the role of H2O. We found that LBP degraded faster in alkaline solutions than in neutral or acidic solutions with or without O2. Degradation rates of LBP increased linearly from pH 4 to 10. Density functional theory calculations showed that OH- initiated the decomposition of LBP through breaking the P–P bond and forming a P–O bond. The detection of hypophosphite, generated from OH- reacting with P atoms, confirmed the hypothesis. Protons acted in a way distinctive from OH-, by inducing deposition/aggregation or forming a cation-π layer to protect LBP from degradation. This work revealed the exact degradation mechanism of LBP to facilitate the development of effective stabilization technologies.
关键词： Degradation mechanism,Hydroxide ion,Nanostructures,Density functional calculations,Black phosphorus
更新于2025-09-10 09:29:36
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Visible-light-driven CeO2/black phosphorus heterostructure with enhanced photocatalytic performance
摘要： CeO2/black phosphorus (BP) heterostructure nanocomposite was synthesized via a two-step assembly method. The structure and optical property of the prepared composites were characterized by X-ray diffraction, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy (UV–Vis), Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Photocatalytic degradation of bisphenol A (BPA) in simulated waste water was performed by using CeO2/BP nanocomposite as catalyst. Results indicated that the degradation rate of BPA reached 82.3% within 180 min, which was remarkably improved compared with pure CeO2 and BP due to the formation of indirect Z-scheme heterostructure intermediated by oxygen vacancies originated from CeO2. The unique heterostructure facilitated the charge transfer and preserved the high redox potential leading to improve the photocatalytic degradation performance.
关键词： photocatalytic degradation,heterostructure,bisphenol A,oxygen vacancies,CeO2/black phosphorus
更新于2025-09-10 09:29:36
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Magnetic field-induced electronic phase transition in the Dirac semimetal state of black phosphorus under pressure
摘要： Different instabilities have been confirmed to exist in the three-dimensional (3D) electron gas when it is confined to the lowest Landau level in the extreme quantum limit. The recently discovered 3D topological semimetals offer a good platform to explore these phenomena due to the small sizes of their Fermi pockets, which means the quantum limit can be achieved at relatively low magnetic fields. In this work, we report the high-magnetic-field transport properties of the Dirac semimetal state in pressurized black phosphorus. Under applied hydrostatic pressure, the band structure of black phosphorus goes through an insulator-semimetal transition. In the high pressure topological semimetal phase, anomalous behaviors are observed on both magnetoresistance and Hall resistivity beyond the relatively low quantum limit field, which is demonstrated to indicate the emergence of an exotic electronic state hosting a density wave ordering. Our findings bring the first insight into the electronic interactions in black phosphorus under intense field.
关键词： High magnetic field,Electron phase transition,Quantum limit,Black phosphorus
更新于2025-09-10 09:29:36
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Photonic spin Hall effect of monolayer black phosphorus in the Terahertz region
摘要： As a two-dimensional (2D) material, black phosphorus (BP) has attracted significant attention owing to exotic physical properties such as low-energy band gap, high carrier mobility, and strong in-plane anisotropy. The striking in-plane anisotropy is a promising candidate for novel light-matter interaction. Here, we investigate the photonic spin Hall effect (PSHE) on a monolayer of BP. Due to the in-plane anisotropic property of BP, the PSHE is accompanied with Goos-H?nchen and Imbert-Fedorov effects, resulting in an asymmetric spin splitting. The asymmetric spin splitting can be flexibly tuned by the angle between the incident plane and the armchair crystalline direction of BP and by the carrier density via a bias voltage. The centroid displacements of two opposite spin components of the reflected beam along directions parallel and perpendicular to the incident plane can be considered as four independent channels for information processing. The potential application in barcode-encryption is proposed and discussed. These findings provide a deeper insight into the spin-orbit interaction in 2D material and thereby facilitate the development of optoelectronic devices in the Terahertz region.
关键词： in-plane anisotropy,two-dimensional material,black phosphorus,photonic spin Hall effect
更新于2025-09-10 09:29:36
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High-performance black phosphorus field-effect transistors with long-term air-stability
摘要： Two-dimensional layered materials (2DLMs) are of considerable interest for high-performance electronic devices for their unique electronic properties and atomically thin geometry. However, the atomically thin geometry makes their electronic properties highly susceptible to the environment changes. In particular, some 2DLMs (e.g., black phosphorus (BP) and SnSe2) are unstable and could rapidly degrade over time when exposed to ambient conditions. Therefore, the development of proper passivation schemes that can preserve the intrinsic properties and enhance their lifetime represents a key challenge for these atomically thin electronic materials. Herein we introduce a simple, non-disruptive and scalable van der Waals passivation approach by using organic thin films to simultaneously improve the performance and air stability of BP field-effect transistors (FETs). We show that dioctylbenzothienobenzothiophene (C8-BTBT) thin films can be readily deposited on BP via van der Waals epitaxy approach to protect BP against oxidation in ambient conditions over 20 days. Importantly, the non-covalent van der Waals interface between C8-BTBT and BP effectively preserves the intrinsic properties of BP, allowing us to demonstrate high-performance BP FETs with a record-high current density of 920 μA/um, hole drift velocity over 1 ⅹ 107 cm/s, and on/off ratio of 104~107 at room temperature. This approach is generally applicable to other unstable two-dimensional (2D) materials, defining a unique pathway to modulate their electronic properties and realize high-performance devices through hybrid heterojunctions.
关键词： black phosphorus,saturation velocity,saturation current density,two-dimensional materials,passivation,field effect transistors
更新于2025-09-10 09:29:36
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Anisotropic Electron–Phonon Interactions in Angle-Resolved Raman Study of Strained Black Phosphorus
摘要： Few layer black phosphorus (BP) with in-plane puckered crystalline structure has attracted intense interest for strain engineering owing to both its significant anisotropy in mechanical and electrical properties as well 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 effect in the DFT emulations, we rebuilt both trends reported for Raman modes shift. 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 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 strain engineering of electrical and optical properties in BP and alike two-dimensional (2D) nano materials.
关键词： black phosphorus,anisotropic Poisson’s ratio,electron-phonon interactions,angle-resolved Raman spectroscopy,strain engineering
更新于2025-09-10 09:29:36
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Double carrier transport in electron-doped region in black phosphorus FET
摘要： Double carrier transport has been observed in thin film black phosphorus (BP) field effect transistor devices in the highly electron-doped region. BP thin films with a typical thickness of 15 nm were encapsulated by hexagonal boron nitride thin films to avoid degradation by air exposure. Their Hall mobility reached 5300 cm2/V s and 5400 cm2/V s at 4.2 K in the hole- and electron-doped regions, respectively. The gate voltage dependence of conductivity exhibits an anomalous shoulder structure in the electron-doped region. In addition, at gate voltages above the shoulder, the magnetoresistance changes to positive, and there appears an additional slow Shubnikov-de Haas oscillation. These results strongly suggest the appearance of second carriers, which originate from the second subband with a localized band edge.
关键词： black phosphorus,Shubnikov-de Haas oscillation,double carrier transport,electron-doped region,field effect transistor
更新于2025-09-10 09:29:36