Black phosphorus is a two-dimensional material of great interest, in part because of its high carrier mobility and thickness dependent direct bandgap. However, its instability under ambient ...conditions limits material deposition options for device fabrication. Here we show a black phosphorus ink that can be reliably inkjet printed, enabling scalable development of optoelectronic and photonic devices. Our binder-free ink suppresses coffee ring formation through induced recirculating Marangoni flow, and supports excellent consistency (< 2% variation) and spatial uniformity (< 3.4% variation), without substrate pre-treatment. Due to rapid ink drying (< 10 s at < 60 °C), printing causes minimal oxidation. Following encapsulation, the printed black phosphorus is stable against long-term (> 30 days) oxidation. We demonstrate printed black phosphorus as a passive switch for ultrafast lasers, stable against intense irradiation, and as a visible to near-infrared photodetector with high responsivities. Our work highlights the promise of this material as a functional ink platform for printed devices.Atomically thin black phosphorus shows promise for optoelectronics and photonics, yet its instability under environmental conditions and the lack of well-established large-area synthesis protocols hinder its applications. Here, the authors demonstrate a stable black phosphorus ink suitable for printed ultrafast lasers and photodetectors.
Abstract
Defects can induce drastic changes of the electronic properties of two-dimensional transition metal dichalcogenides and influence their applications. It is still a great challenge to ...characterize small defects and correlate their structures with properties. Here, we show that tip-enhanced Raman spectroscopy (TERS) can obtain distinctly different Raman features of edge defects in atomically thin MoS
2
, which allows us to probe their unique electronic properties and identify defect types (e.g., armchair and zigzag edges) in ambient. We observed an edge-induced Raman peak (396 cm
−1
) activated by the double resonance Raman scattering (DRRS) process and revealed electron–phonon interaction in edges. We further visualize the edge-induced band bending region by using this DRRS peak and electronic transition region using the electron density-sensitive Raman peak at 406 cm
−1
. The power of TERS demonstrated in MoS
2
can also be extended to other 2D materials, which may guide the defect engineering for desired properties.
The rapidly emerging field of 2D magnetic materials has garnered significant attention due to its fascinating physical properties and wide‐ranging potential applications. This review highlights the ...importance of magneto‐optical interactions as a crucial tool for both studying and modulating 2D magnets. It offers a comprehensive survey of current research concerning magneto‐optical interactions in 2D magnetic materials, encompassing the magneto‐optical Kerr effect, reflection magnetic circular dichroism, second‐harmonic generation, photoluminescence, inelastic light scattering, and time‐resolved spectroscopy. This review discusses how these techniques provide insights into the properties of 2D magnets, enabling exploration of magnetic phase transitions, lattice alterations, spin dynamics, as well as their responses to external fields. Moreover, it emphasizes the modulation of magnetic properties by photo‐stimulation and offers a brief outlook on this swiftly developing field.
This review synthesizes recent progress in investigating magneto‐optical interactions in 2D magnetic materials. It categorizes advancements by interaction type, exploring their insights into the properties like magnetic phase transitions, lattice alterations, and spin dynamics, and examines field modulation of optical signals for each interaction. It offers an outlook on the rapidly evolving field of magneto‐optical interactions in 2D magnets.
Anisotropic photonic materials with linear dichroism are crucial components in many sensing, imaging, and communication applications. Such materials play an important role as polarizers, filters, and ...waveplates in photonic devices and circuits. Conventional crystalline materials with optical anisotropy typically show unidirectional linear dichroism over a broad wavelength range. The linear dichroism conversion phenomenon has not been observed in crystalline materials. The investigation of the unique linear dichroism conversion phenomenon in quasi‐1D hexagonal perovskite chalcogenide BaTiS3 is reported. This material shows a record level of optical anisotropy within the visible wavelength range. In contrast to conventional anisotropic optical materials, the linear dichroism polarity in BaTiS3 makes an orthogonal change at an optical wavelength corresponding to the photon energy of 1.78 eV. First‐principles calculations reveal that this anomalous linear dichroism conversion behavior originates from the different selection rules of the parallel energy bands in the BaTiS3 material. Wavelength‐dependent polarized Raman spectroscopy further confirms this phenomenon. Such a material, with linear dichroism conversion properties, could facilitate the sensing and control of the energy and polarization of light, and lead to novel photonic devices such as polarization‐wavelength selective detectors and lasers for multispectral imaging, sensing, and optical communication applications.
The linear dichroism conversion phenomenon is reported in quasi‐1D hexagonal perovskite chalcogenide BaTiS3, which also shows a record level of optical anisotropy in the visible range. Wavelength‐dependent polarization‐resolved Raman spectroscopy and first‐principles calculations further confirm the orthogonal cross‐over of the linear dichroism polarity in this material. This discovery could lead to novel photonic devices for multispectral imaging, sensing, and communication.
The electron-phonon coupling (EPC) in a material is at the frontier of the fundamental research, underlying many quantum behaviors. van der Waals heterostructures (vdWHs) provide an ideal platform to ...reveal the intrinsic interaction between their electrons and phonons. In particular, the flexible van der Waals stacking of different atomic crystals leads to multiple opportunities to engineer the interlayer phonon modes for EPC. Here, in hBN/WS
vdWH, we report the strong cross-dimensional coupling between the layer-breathing phonons well extended over tens to hundreds of layer thick vdWH and the electrons localized within the few-layer WS
constituent. The strength of such cross-dimensional EPC can be well reproduced by a microscopic picture through the mediation by the interfacial coupling and also the interlayer bond polarizability model in vdWHs. The study on cross-dimensional EPC paves the way to manipulate the interaction between electrons and phonons in various vdWHs by interfacial engineering for possible interesting physical phenomena.
The quantum confinement in atomic scale and the presence of interlayer coupling in multilayer make the electronic and optical properties of 2D materials (2DMs) be dependent on the layer number (N) ...from monolayer to multilayer. Optical properties of 2DMs have been widely probed by several optical techniques, such as optical contrast, Rayleigh scattering, Raman spectroscopy, optical absorption, photoluminescence, and second harmonic generation. Here, it is reviewed how optical properties of several typical 2DMs (e.g., monolayer and multilayer graphenes, transition metal dichalcogenides) probed by these optical techniques significantly depend on N. Further, it has been demonstrated how these optical techniques service as fast and nondestructive approaches for N counting or thickness determination of these typical 2DM flakes. The corresponding approaches can be extended to the whole 2DM family produced by micromechanical exfoliations, chemical‐vapor‐deposition growth, or transfer processes on various substrates, which bridges the gap between the characterization and international standardization for thickness determination of 2DM flakes.
Optical properties of 2D materials, such as optical contrast, Rayleigh scattering, Raman spectroscopy, optical absorption, photoluminescence, and second harmonic generation, are dependent on the layer number. Here, we demonstrate how these optical techniques serve as fast and nondestructive approaches for layer number counting or thickness determination of these typical 2D material flakes.
The successful fabrication of a two-dimensional boron sheet, which features a triangular lattice with periodic hole arrays, has stimulated great interest in its specific structure as well as ...properties such as possible superconductivity. Here, we report a study on the vibrational spectra and electron–phonon coupling (EPC) in monolayer boron sheets by in situ Raman and tip-enhanced Raman spectroscopy (TERS) at low temperature and ultrahigh vacuum. The gap-mode TERS gives a 3 × 109 selective enhancement on vertical vibrational Raman modes. A spatial resolution of 1 nm is achieved in this system. Combined with first-principle calculations, the vibrational properties as well as EPC in borophene are determined. The results are helpful for further study on the mechanical, electronic, and possible superconducting properties of two-dimensional boron.
Combining ultrahigh sensitivity, spatial resolution, and the capability to resolve chemical information, tip-enhanced Raman spectroscopy (TERS) is a powerful tool to study molecules or nanoscale ...objects. Here we show that TERS can also be a powerful tool in studying two-dimensional materials. We have achieved a 10^{9} Raman signal enhancement and a 0.5 nm spatial resolution using monolayer silicene on Ag(111) as a prototypical 2D material system. Because of the selective enhancement on Raman modes with vertical vibrational components in TERS, our experiment provides direct evidence of the origination of Raman modes in silicene. Furthermore, the ultrahigh sensitivity of TERS allows us to identify different vibrational properties of silicene phases, which differ only in the bucking direction of the Si-Si bonds. Local vibrational features from defects and domain boundaries in silicene can also be identified.
The extraordinary thermal and elastic properties of graphene, mainly originating from its unique acoustic phonon branches near Γ point in Brillouin zone, have attracted great attention in its ...fundamental researches and practical applications. Here, we introduce an optical technique to accurately probe longitudinal acoustic (LA) and transverse acoustic (TA) phonon branches of graphene near Γ point by double resonant Raman scattering of the combination phonon modes in the range of 1650−2150 cm−1 along with the overtone 2D' mode at ∼3200 cm−1. The corresponding sound velocities (νTA=12.9km/s,νLA=19.9km/s) of graphene have been accessed, which are about 10% smaller than those of graphite. Based on νTA and νLA, the two-dimensional (2d) elastic stiffness (tension) coefficients c11 and c66, Young's modulus Y2d and Poisson's ratio σ2d can be estimated. The results demonstrate again that double resonant Raman spectroscopy is a powerful tool to probe the fundamental properties of graphene.
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