Black Phosphorus Nanoribbons Research Articles

Spin filtering, magnetoresistance and seebeck effects in phthalocyanine based molecular junctions between phosphorus nanoribbon electrodes

This research utilized the non-equilibrium Green’s function (NEGF) method combined with density functional theory (DFT) to explore spin transport in binuclear transition metal phthalocyanine (TMPc) molecules between black phosphorus nanoribbon electrodes. The device achieves near 100% SFE with ferromagnetic coupling of Manganese phthalocyanine (MnPc) and Iron phthalocyanine (FePc). When the MnPc and FePc molecules exhibited anti-ferromagnetic coupling, with the transports in the two spin channels significantly smaller than in the ferromagnetic coupling scenario, demonstrating giant magnetoresistance effects. MnPc shows high Seebeck polarization at 149 K, while FePc maintains it at a low temperature. This research opens new avenues for designing molecular spintronic devices with two-dimensional electrodes.

Semiconducting black phosphorus nanoribbons grown on insulating substrates.

Semiconducting black phosphorus nanoribbons grown on insulating substrates.

Seeded growth of single-crystal black phosphorus nanoribbons.

Two-dimensional materials have emerged as an important research frontier for overcoming the challenges in nanoelectronics and for exploring new physics. Among them, black phosphorus, with a combination of a tunable bandgap and high mobility, is one of the most promising systems. In particular, black phosphorus nanoribbons show excellent electrostatic gate control, which can mitigate short-channel effects in nanoscale transistors. Controlled synthesis of black phosphorus nanoribbons, however, has remained an outstanding problem. Here we report large-area growth of black phosphorus nanoribbons directly on insulating substrates. We seed the chemical vapour transport growth with black phosphorus nanoparticles and obtain uniform, single-crystal nanoribbons oriented exclusively along the [100] crystal direction. With comprehensive structural calculations, we discover that self-passivation at the zigzag edges holds the key to the preferential one-dimensional growth. Field-effect transistors based on individual nanoribbons exhibit on/off ratios up to ~104, confirming the good semiconducting behaviour of the nanoribbons. These results demonstrate the potential of black phosphorus nanoribbons for nanoelectronic devices and also provide a platform for investigating the exotic physics in black phosphorus.

Role of Edge Reconstruction in the Synthesis of Few-Layer Black Phosphorene.

Recent advancements in preparing few-layer black phosphorene (BP) are hindered by edge reconstruction challenges. Our previous studies have revealed the factors contributing to the difficulty of growing few-layer BP. In this study, we have successfully identified three reconstructed edges in bi- and multilayer BP through a combination of the crystal structure analysis by particle swarm optimization (CALYPSO) global structure search and density functional theory (DFT). Notably, the reconstruction between adjacent layers proves more beneficial than self-passivation or maintaining pristine edges. Among the reconstructed edges, the reconstructed ZZ edge is the most stable, regardless of the number of layers. Calculated electronic band structures reveal a significant transition in the electronic properties of black phosphorus nanoribbons (BPNRs), changing from metallic to semiconducting. This insight not only enhances the understanding of the fundamental properties of BP but also provides valuable theoretical guidance for the experimental growth of BPNRs or black phosphorus nanowires (BPNWs).

Edge-Confined Excitons in Monolayer Black Phosphorus.

Quantum confinement of two-dimensional excitons in van der Waals materials via electrostatic trapping, lithographic patterning, Moiré potentials, and chemical implantation has enabled significant advances in tailoring light emission from nanostructures. While such approaches rely on complex preparation of materials, natural edges are a ubiquitous feature in layered materials and provide a different approach for investigating quantum-confined excitons. Here, we observe that certain edge sites of monolayer black phosphorus (BP) strongly localize the intrinsic quasi-one-dimensional excitons, yielding sharp spectral lines in photoluminescence, with nearly an order of magnitude line width reduction. Through structural characterization of BP edges using transmission electron microscopy and first-principles GW plus Bethe-Salpeter equation (GW-BSE) calculations of exemplary BP nanoribbons, we find that certain atomic reconstructions can strongly quantum-confine excitons resulting in distinct emission features, mediated by local strain and screening. We observe linearly polarized luminescence emission from edge reconstructions that preserve the mirror symmetry of the parent BP lattice, in agreement with calculations. Furthermore, we demonstrate efficient electrical switching of localized edge excitonic luminescence, whose sites act as excitonic transistors for emission. Localized emission from BP edges motivates exploration of nanoribbons and quantum dots as hosts for tunable narrowband light generation, with future potential to create atomic-like structures for quantum information processing applications as well as exploration of exotic phases that may reside in atomic edge structures.

Transparency window in the THz frequency based on asymmetric dark-dark modes interaction

In this study, we investigate the impact of asymmetry on plasmonic-induced transparency (PIT) in structures with double dark modes. We have identified the ideal structural parameters for the single and double asymmetric dark mode structures, and it has been demonstrated that the usage of these factors improves sensing performance. The suggested structure is made up of a number of parallel black phosphorus nano-ribbons (BPNRs) with similar length, and it has been found that double asymmetric dark-dark systems creates a more stable and consistent transparency window, making it a strong contender to serve as a refractive index sensor. The proposed structure is simple and easy to manufacture, making it a more viable design for refractive index sensors for the terahertz range.

DC and RF Performance of an N-channel Monolayer Black Phosphorus Nanoribbon Transistor

Two-dimensional black phosphorus is a relatively new discovery. There are numerous studies on black phosphorus two-dimensional transistors that focus on analog and RF performance. However, the RF performance of black phosphorus nanoribbon transistors is yet to be explored. We use a four-band tight binding Hamiltonian in conjunction with a non-equilibrium Green's function quantum transport simulator to investigate both the DC and RF performance of a monolayer black phosphorus nanoribbon transistor. We found that electron intra-band tunneling is responsible for current flow in the off-state, while in the on-state, the electrons flow over the top of the channel barrier potential. With a VDD of 0.4 volt and a gate length of 5 nm, our black phosphorus nanoribbon transistor has DC performance metrics of 510 µA/µm on-state current, 105 on/off current ratio, and 65 mV/dec inverse subthreshold slope. The device's RF performance characteristics are as follows: cut-off (unity current gain) frequency of 772.84 GHz, maximum oscillation (unity power gain) frequency of 1.15 THz, and open circuit voltage gain of 26.7 dB with transistor operating in the on-state. The RF performance of the device is found to be significantly impacted by the source and drain contact resistances. With source and drain resistances set to zero, the cut-off frequency increases to 995.23 GHz and the unity power gain frequency increases to 4.16 THz. The device shows unconditional stability above 893 GHz and it is conditionally stable below this frequency.

Narrow Directed Black Phosphorus Nanoribbons Produced by A Reformative Mechanical Exfoliation Approach (Small 17/2023)

Narrow Directed Black-Phosphorus Nanoribbons The preparation of high-quality narrow black phosphorus nanoribbons (PNRs) aligned along the same direction is very challenging. In article number 2207538, Changxin Chen and co-workers develop a reformative mechanical exfoliation approach combining tape and polydimethylsiloxane (PDMS) exfoliations to fabricate high-quality, narrow and directed PNRs with smooth edges. The prepared PNRs have widths from a dozen to hundreds of nanometers and can align along a same direction with their length directions along the zigzag direction.

Narrow Directed Black Phosphorus Nanoribbons Produced by A Reformative Mechanical Exfoliation Approach.

Black phosphorus nanoribbons (PNRs) are ideal candidates for constructing electronic and optoelectronic devices owing to their unique structure and high bandgap tunability. However, the preparation of high-quality narrow PNRs aligned along the same direction is very challenging. Here, a reformative mechanical exfoliation approach combining tape and polydimethylsiloxane (PDMS) exfoliations to fabricate high-quality, narrow, and directed PNRs with smooth edges for the first time is developed. In this method, partially-exfoliated PNRs are first formed on thick black phosphorus (BP) flakes via the tape exfoliation and further peeled off to obtain separated PNRs via the PDMS exfoliation. The prepared PNRs have widths from a dozen to hundreds of nanometers (down to 15nm) and a mean length of 18µm. It is found that the PNRs can align along a same direction and the length directions of directed PNRs are along the zigzag direction. The formation of PNRs is attributed to that the BP prefers to be unzipped along the zigzag direction and has an appropriate magnitude of interaction force with the PDMS substrate. The fabricated PNR/MoS2 heterojunction diode and PNR field-effect transistor exhibit good device performance. This work provides a new pathway to achieve high-quality, narrow, and directed PNRs for electronic and optoelectronic applications.

Demonstration of giant anisotropic magnetoresistance, high spin filtering efficiency, and negative differential resistance in nanodevices based on oxygen doped black arsenic phosphorus nanoribbons

We investigate the electrical properties of pure black arsenic phosphorus and oxygen atom doped monolayer black arsenic phosphorus using first principle calculations. The density of states results reveals that oxygen atom doped black arsenic phosphorus is a magnetic semiconductor. The current-voltage characteristic curves of oxygen atom doped monolayer black arsenic phosphorus nanoribbons based devices have been determined using the non-equilibrium Green's function associated with the density function theory. The results demonstrate that the device made of doped black arsenic phosphorus has a substantial current difference between armchair and zigzag black arsenic phosphorus nanoribbons, implying that the device made of nanoribbons has a large anisotropic magnetoresistance. The spin filtering efficiency is nearly 100% at some bias voltage levels, and the transmission spectrums of the associated bias voltage window can explain the significant negative differential resistance. Furthermore, these findings suggest that oxygen atom doped black arsenic-phosphorus nanoribbons are suitable for spintronic devices.

Enhanced linear dichroism of flattened-edge black phosphorus nanoribbons

Black phosphorus is a material with an intrinsic anisotropy in electronic and optical properties due to its puckered honeycomb lattice. Optical absorption is different for incident light with linear polarization in the armchair and zigzag directions (linear dichroism). These directions are also used in the cuts of materials to create black phosphorus nanoribbons. Edges of nanoribbons usually have small reconstruction effects, with minor electronic effects. Here, we show a reconstruction of the armchair edge that introduces a new valence band, which flattens the puckered lattice and increases the linear dichroism extrinsically in the visible spectrum. This enhancement in linear dichroism is explained by the polarization selection rule, which considers the parity of the wave function to a reflection plane. The flattened-edge reconstruction originates from the inversion of chirality of the P atoms at the edges and significantly alters the entire optical absorption of the material. The flattened edges have potential applications in pseudospintronics, photodetectors and might provide new functionalities in optoelectronic and photonic devices.

Dynamically Tunable Plasmon-Induced Transparency in Parallel Black Phosphorus Nanoribbons

In this paper, we investigate the dynamically tunable plasmon-induced transparency (PIT) effects in parallel black phosphorus nanoribbons (BPNRs). The proposed structures consist of several parallel BPNRs having different lengths in one transverse period. The periods of all proposed structures are set as \(P = 500 \, nm\). To our best knowledge, these proposed structures have not been reported in published papers. It is the first time that simulates PIT effects by this way. The results show that the BPNRs can be regarded as bright modes. Single-band, double-band, triple-band, and multi-band PIT effects based on the bright-bright mode coupling between parallel BPNRs are achieved. The physical mechanism of the single-band model can be explained theoretically by the radiating two-oscillator (RTO) model. Due to the heavier effective mass in the zigzag (ZZ) direction of the BP, the frequencies of the transparent peaks are shifted to lower frequencies when the placement directions of BPNRs are changed from the X-direction to the Y-direction. Furthermore, the resonant frequencies of the transparent windows in each model can be tuned by changing the relaxation rates of the BPNRs. The frequencies of the transparent windows are blue-shifted as the relaxation rates are increased. Finally, the corresponding sensors based on single-band PIT effect show high sensitivities of 7.35 THz/RIU. Our study has potential applications for improving the design of multiple-band filters, sensors, and on–off switcher.

Effects of interface charge-transfer doping on thermoelectric transport properties of black phosphorene-F4TCNQ nanoscale devices

Using first-principle-based density functional theory (DFT) combined with non-equilibrium Green's function (NEGF) method, we carry out a systematic study on thermoelectric transport properties of both armchair and zigzag black phosphorus nanoribbons (APNR and ZPNR) with physical adsorption of molecule F4TCNQ on their surfaces. The results indicate that APNR/F4TCNQ system is presented as a p-type semiconductor, and valence band edge of APNR system shifts to Fermi level (FL) due to surface charge transfer from APNR to F4TCNQ. Compared with pure APNR, thermal power S of APNR with F4TCNQ adsorption is increased from 270.8 μV/K to 1063 μV/K owing to the increase of state density induced from the emergence of resonance energy level near FL. Moreover, interface coupling and quantum interference effects inhibit phonon thermal conductance of A/ZPNR + F4TCNQ system significantly, and optimal thermoelectric figure of merit ZT of ZPNR/F4TCNQ system achieves 0.72 when μ = −0.5 eV at room temperature. This work provides a possibility for extensive application of high-performance two-dimensional organic–inorganic nanodevices in thermoelectric field, and it also has theoretical reference for developing self-assembled electronic device in practical applications.

Design of a broadband infrared absorber based on multiple layers of black phosphorus nanoribbons

A polarization-sensitive broadband plasmonic absorber consists of multiple black phosphorus (BP)/dielectric layers stacking on an Ag reflector has been proposed theoretically and demonstrated numerically for infrared (IR) regime. The optimum geometrical parameters have been achieved by parametric sweep analyses with regard to the fabrication considerations and miniaturization of the absorber structure. So a high absorption (above 85%) with relatively broad bandwidth of 5.24 µm corresponding to the relative bandwidth of 42.12% has been achieved for the designed periodic structure with optimum unit cell dimensions of 0.5 µ m × 1.755 µ m . The electromagnetic loss in the BP material is the foundation of absorption performance in the designed absorber. The proposed anisotropic broadband IR absorber may have great potential in many areas of photonics.

Anisotropic thermal conductivity and corrugated patterns in single-layer black phosphorus nanoribbon subjected to shear loading: a molecular dynamics study

Single-layer black phosphorus (SLBP) also known as phosphorene is a recently introduced two-dimensional material with unique structure and promising physical properties that has drawn considerable attention in the field of nanodevices. This structure demonstrates a high anisotropy in mechanical and thermal behavior along zigzag (ZZ) and armchair (AC) principal in-plane directions. Here in this study, it is shown that implementing shear strain on 10 nm × 50 nm SLBP nanoribbons (SLBPNRs) along ZZ and AC directions, the anisotropy leads to different corrugated patterns on the pristine structure. Applying non-equilibrium molecular dynamics under a parameterized Stillinger–Weber potential for modelling SLBP, thermal conductivity (TC) behavior of the sheared SLBPNRs with corrugated patterns are examined. The results show a higher amplitude and wavelength of the corregations on the ZZ-aligned SLBPNRs, which is around two times higher than that of AC-aligned counterparts. Although, it is also shown that unlike some other 2D materials, such as graphene, the wrinkling does not have such a significant effect on TC of SLBP. The phonon density of states results obtained in this work as well as phonon dispersion curves by first-principle calculations in other works concrete this finding. The results show small frequency shifts in both high- and low-frequency phonons, which are not strong enough to affect TC in SLBPNRs. This interesting thermal property of SLBP under shear strain suggests the great potential application of these corrugated structures in nanodevices without any loss of TC abilities.

Chemical Vapor Transport Route toward Black Phosphorus Nanobelts and Nanoribbons.

Chemical vapor transport (CVT) method is widely used for bulk black phosphorus (BP) fabrication. In this work, we demonstrate that CVT provides a route for the fabrication of BP nanoribbons and nanobelts. This method consists of a two-step procedure, including initial BP column growth using the CVT technique, followed by ultrasonic treatment and centrifugation. The obtained nanostructures preserve BP column dimensions, forming ultralong ribbon-like structures with the length to the width aspect ratio of up to 500. Computational modeling of the growth mechanism of a BP flake is also presented in support of the observed columnar growth. Calculation of the average energy of the molecule in the asymmetric flakes shows that the growth of the structure in the zigzag direction is more energetically favorable than in the armchair direction.

Active control of plasmon-induced transparency with large tunability and high Q-factor in graphene-black phosphorus hybrid system

Plasmon-induced transparency phenomena in the mid-infrared caused by the coupling behavior between dipole (bright element) and higher-order modes (dark element) in graphene as well as black phosphorus (BP) nanoribbons are investigated. The transparent windows can be adjusted flexibly by varying the carrier concentration of graphene and BP. It is also shown that the carrier mobility and refractive index of the substrate are the key factors affecting destructive interference. Obvious group delays are obtained near the transparent windows so that the slow light effect can be achieved. Our results allow a better understanding of efficient exploration of surface plasmons with integrated properties of building blocks from a family of two-dimensional materials, with the aim of expanding both photonic bands and functionalities.

Critical role of the bending stiffness of the monolayer black phosphorus in its mechanical behaviors: molecular dynamics simulation

Black phosphorus (BP) is a novel two-dimensional nanostructure with wide potential applications in such areas as nanoresonators and nanosensors. In this study, we concentrate on the role of the bending stiffness of the BP monolayer in its mechanical performances, including tension, compression, buckling and bending. Firstly, the stress–strain curve and Young’s modulus of the single layer black phosphorus (SLBP) nanoribbon with different chiral structures are obtained in the tension process via the molecular dynamics (MD) simulation. Next, the loading behavior of the SLBP nanoribbon during compression is simulated via MD. It was found that the bending stiffness of the nanoribbon has an essential effect on its postbuckling behaviors, and an empirical formula is proposed which can accurately depict the postbuckling process. Eventually, the bending properties of chiral SLBP nanoribbons are explored via the MD simulation, and the modified expression of the bending stiffness can better predict its large deflection. These findings are beneficial for us to fully understand mechanical responses of BP, which hold implications in engineering new materials and devices at nanoscale.

Excitons in bent black phosphorus nanoribbons: multiple excitonic funnels

Quasi-one-dimensional nanoribbons (NRs) are promising candidate materials for flexible optoelectronics with high device density. The optical properties of nanomaterials are strongly influenced by excitons, and it is important for flexible devices to explore how excitons behave under strain. In this work, we investigate the electronic and excitonic properties of bent black phosphorus (BP) NRs via density-functional theory and many-body Green's function methods. We find that inhomogeneous strain fields affect not only the first excitonic energy and thus the optical gap, but also the spatial distribution of the excitons. In particular, excitonic funnels can occur in bent black phosphorus nanoribbons (BPNRs), which drive higher-energy excitons toward lower energy locations. The funnels can be effectively tuned by the intensity and sign (compressed to tensile) of the strain field. Another critical factor is anisotropy: the funnel effect is much more pronounced in armchair BPNRs than in zigzag BPNRs. In addition, we find that the excitonic funnel effect in two-dimensional monolayer BP differs from that in multilayer BP films.

Prospects of black phosphorus nanoribbon for explosive sensing: A computational approach

We have explored the possibility of using a low-dimensional black phosphorus-based nanoscale device for the detection of nitroaromatic-based explosives. In this work, we have investigated the structural, electronic, adsorption, and quantum transport properties of phosphorene nanoribbon (APNR) in the presence of different nitroaromatic compounds (NACs) using the state-of-the-art first-principle density functional theory (DFT) calculations. Our results reveal that the explosive molecules are interacting with the APNR surface, which neither affects the structure of the explosive molecule nor the APNR surface. However, it changes the electronic energy-gap due to the charge transfer between the APNR and explosive molecule. Furthermore, we have examined the transmission function and the current-voltage (I-V) characteristic curves for the APNR + explosive systems with the APNR device as a reference employing the non-equilibrium Green’s function (NEGFs) combined with DFT approach. The different current-voltage characteristics (compared to pristine APNR device) of the system in the presence of explosive molecules indicate that such APNR based device can be very much sensitive and selective towards certain explosive molecules. Hence, our study demonstrates that APNR material may be an attractive nanodevice for the detection of explosives.