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abstract: We perform a comprehensive first principles study of the electronic properties of phosphorene nanoribbons, phosphorus nanotubes, multilayer phosphorene sheets, and heterobilayers of phosphorene and two dimensional (2D) transition metal dichalcogenide (TMDC) monolayer. The tensile strain and electric field effects on electronic properties of low dimensional phosphorene nanostructures are also investigated. Our calculations show that the bare zigzag phosphorene nanoribbons (z PNRs) are metals regardless of the ribbon width, whereas the bare armchair phosphorene nanoribbons (a PNRs) are semiconductors with indirect bandgaps and the bandgaps decrease with increasing ribbon width. We find that compressive (or tensile) strains can reduce (or enlarge) the bandgap of the bare a PNRs while an in plane electric field can significantly reduce the bandgap of the bare a PNRs, leading to the semiconductor to metal transition beyond certain electric field. For edge passivated PNR by hydrogen, z PNRs become semiconductor.
author_names: Hongyan Guo

Ning Lu

Jun Dai

Xiaojun Wu

Xiao Cheng Zeng
title: Phosphorene Nanoribbons, Phosphorus Nanotubes, and van der Waals Multilayers
year: 2014

abstract: The structural and electronic properties of few layers of blue phosphorus and their van der Waals heterostructures with graphene were investigated by means of first principles electronic structure calculations. We study the four energetically most stable stacking configurations for multilayers of blue phosphorus. For all of them, the indirect band gap semiconductor character, are preserved. We show that the properties of monolayer graphene and single layer (bilayer) blue phosphorus are preserved in the van der Waals heterostructures. Further, our results reveal that under a perpendicular applied electric field, the position of the band structure of blue phosphorus with respect to that of graphene is tunable, enabling the effective control of the Schottky barrier height. Indeed, for the bilayer blue phosphorene on top of graphene, it is possible to even move the system into an Ohmic contact and induce a doping level of the blue phosphorene. All of these features are fundamental for the design of new nanodevices based on van der Waals heterostructures.
author_names: Renato Borges Pontes

Roberto H Miwa

Antonio J R da Silva

Adalberto Fazzio

Jose Eduardo Padilha
title: Layer dependent band alignment of few layers of blue phosphorus and their van der Waals heterostructures with graphene
year: 2018

abstract: Controlled syntheses in nanoscale structures should be expected and phosphorous nanotubes with predefined chiralities are important in electronic devices with tunable bandgap. Here, incorporating molecular dynamics simulations with theoretical analyses, we show that a zigzag phosphorene nanoribbon can self assemble and form a corresponding chiral phosphorous nanotube surrounding a template armchair phosphorous nanotube. The van der Waals potential between the nanoribbon and the nanotube is transformed to the intrinsic deformed and chemical bonding energies of the synthesized tube together with partial kinetic energy. The self assembly process has an apparent temperature dependence and size effect and the formed chiral tube is thermodynamically stable. Also, the chirality and measurement can be tuned by the radius of template tube and the aspect ratio of raw ribbon. The study suggests a novel and feasible approach for controlled synthesis of phosphorous nanotubes and thus is of great interest for semiconductor device applications.
author_names: Douxing Pan

Tzuchiang Wang

Chao Wang

Wei Guo

Yugui Yao
title: Self assembled chiral phosphorus nanotubes from phosphorene: a molecular dynamics study
year: 2016

abstract: Structural evolution induced and driven by a dual system and simultaneous passivation of phosphorene are reported. Different nano objects of phosphorene or black phosphorus (BP) are obtained using a new method of exfoliation, in which solvent and an ionic polymer are combined to weaken the van der Waals forces and to scissor the nanosheets. Nanoribbons, nanorods, and nanoneedles are obtained under mechanical force and ambient conditions. Ionic polymer chains assist in curling the monolayer or few layer nanosheet. Nafion is chosen to exfoliate the bulk BP and induce a morphological transition in BP nanosheets. The exfoliation of BP nanosheets results into thin and specific structures such as nanosheets/rods/needles. The nanosheets of phosphorene are covered and passivated simultaneously by the polymeric sheath that protects the nanosheets from degradation or oxidation and can be integrated with a device directly without any further coating.
author_names: Avneesh Kumar
title: Controlled nanostructures and simultaneous passivation of black phosphorus (phosphorene) with Nafion
year: 2020

abstract: Controlled synthesis is always expected in nanoscale structures and phosphorous nanotubes with predefined chiralities are very important to electronic devices with tunable bandgap. Here, we demonstrate by molecular dynamics simulations incorporating theoretical analysis that a zigzag phosphorene nanoribbon can be assembled spontaneously to form a corresponding chiral phosphorous nanotube on the outer side of an armchair phosphorous nanotube. The van der Waals potential between the nanoribbon and the nanotube is transformed to the intrinsic deformed and chemical bonding energy of the synthesized tube together with partial kinetic energy. The self assembly process has an apparent temperature dependence and size effect, and the formed chiral tube is stable thermodynamically and its chirality and measurement can be tuned by the radius of template tube and the length width ratio of raw ribbon. Extensive study shows that the chiral tube can be assembled by a phosphorene ribbon outside the phosphorous tube with isomeric chirality, but not with isomorphic chirality, performing a significant anisotropy; moreover, phosphorene ribbon inside phosphorous tube can not be either assembled into chiral tube, performing a significant location relevance.
author_names: Douxing Pan

Tzuchiang Wang

Yugui Yao

Chao Wang
title: Self assembled chiral phosphorus nanotubes from phosphorene: a dynamic molecular study
year: 2016

abstract: Controlled syntheses in nanoscale structures is expected and phosphorous nanotubes with predefined chiralities are important in electronic devices with tunable bandgap. Herein, by incorporating molecular dynamics simulations and theoretical analyses, we predict that a zigzag phosphorene nanoribbon can self assemble and form a corresponding chiral phosphorous nanotube surrounding a template armchair phosphorous nanotube. The van der Waals potential between the nanoribbon and the nanotube is transformed to the intrinsic deformed and chemical bonding energies of the synthesized tube together with partial kinetic energy. In addition, we show that the self assembly process has an apparent temperature dependence and size effect. The formed chiral tube is thermodynamically stable and its chirality and measurement can be tuned by the radius of the template tube and the aspect ratio of the raw ribbon. Extensive studies demonstrate that the chiral tube can be self assembled by a phosphorene ribbon outside the template phosphorous tube with isomeric chirality, but neither with isomorphic chirality outside, nor inside, indicating significant anisotropy and location relevancy. Our studies suggest a novel and feasible approach for controlled synthesis of phosphorous nanotubes and thus of great interests for semiconductor device applications of two dimensional materials.
author_names: Douxing Pan

Tzuchiang Wang

Chao Wang

Wei Guo

Yugui Yao
title: Self assembled chiral phosphorus nanotubes from phosphorene predicted by molecular dynamics simulations
year: 2016

abstract: Edge induced gap states in finite phosphorene layers are examined using analytical models and density functional theory. The nature of such gap states depends on the direction of the cut. Armchair nanoribbons are insulating, whereas nanoribbons cut in the perpendicular direction (with zigzag and cliff type edges) are metallic, unless they undergo a reconstruction or distortion with cell doubling, which opens a gap. All stable nanoribbons with unsaturated edges have gap states that can be removed by hydrogen passivation. Armchair nanoribbon edge states decay exponentially with the distance to the edge and can be described by a nearly free electron model. Black phosphorus is a van der Waals bonded layered material, and the most stable form of of this element. Its peculiar orthorhombic structure resembling corrugated cardboard sets it apart from other two dimensional materials such as graphene and MoS2. Unlike those, it is highly anisotropic with respect to the directions in plane, [1 4] and therefore it offers new terrain to the exploration of physical phenomena in two dimensional materials. The isolation of the monolayer form, named phosphorene, has been recently achieved by mechanical cleavage followed by plasma thinning [5] and multi layered material is now routinely produced by exfoliation. [6, 7] Both have been theoretically predicted to be direct gap or nearly direct gap semiconductors with energy gaps ranging from 2 eV to 0.8 eV. [8] However, the bandstructure is far from typical. The effective masses for carriers are at least one order of magnitude higher along the direction of the to the zigzag ridges (y) than along the perpendicular direction (x) And the electron and hole masses are nearly the same along x, but very asymmetric along y. Further, due to the weak interaction between second and third nearest neighbors, it can easily be deformed under uniaxial compression, becoming, in sequence, an indirect gap semiconductor, a semimetal, a metal, and ultimately undergoing a transition to a square lattice. [1, 2, 9] Phosphorene can, in principle, be cut and tailored into derived nanostructures [10 12] An interesting feature of finite systems is the possibility of edge states. These states are localized at the system vacuum interface and decay exponentially away from it. The nature of the edge states depends not only on the crystal structure of the system, but also on the way it terminates. Understanding the physics of nanoribbon edges is fundamental for predicting the behavior of real finite systems and for designing more complex nanostructures, such as nanotubes and voids. In this paper, we analyze the electronic states induced by finite edges. We show that armchair edges, cut along the x direction, invariably lead to localized edge states, decaying exponentially towards the bulk. In contrast, edges cut along the y direction were found to introduce less localized states for nanoribbons. All the nanoribons are semiconducting in the large width limit. We first discuss the origin of these localized gap states. In our previous work [1] we have shown that tight binding has a limited utility for black phosphorus. Therefore, we will perform our analysis here using the nearly free electron model (NFEM) Before proceeding with the particular phosphorene case, we provide a derivation of the edge states for the reader's convenience following a standard procedure. We consider edge states in the gap of the infinite monolayer. Since these states are exponentially decaying, they must have an imaginary momentum component perpendicular to the edge. Assuming that the system is located in the negative half plane, the wavefunction inside it is p 1 ar X iv :1 40 4. 51 15 v3 co nd m at .m es h al l] 2 9 A ug 2 01 4 A. Carvalho1 A. S. Rodin1 A. H. Castro Neto1,2
author_names: Alexandra Carvalho

Aleksandr Rodin

Antonio H Castro Neto
title: Phosphorene nanoribbons
year: 2014

abstract: Van der Waals interactions have a fundamental role in biology, physics and chemistry, in particular in the self assembly and the ensuing function of nanostructured materials. Here we utilize an efficient microscopic method to demonstrate that van der Waals interactions in nanomaterials act at distances greater than typically assumed, and can be characterized by different scaling laws depending on the dimensionality and size of the system. Specifically, we study the behaviour of van der Waals interactions in single layer and multilayer graphene, fullerenes of varying size, single wall carbon nanotubes and graphene nanoribbons. As a function of nanostructure size, the van der Waals coefficients follow unusual trends for all of the considered systems, and deviate significantly from the conventionally employed pairwise additive picture. We propose that the peculiar van der Waals interactions in nanostructured materials could be exploited to control their self assembly.
author_names: Vivekanand V Gobre

Alexandre Tkatchenko
title: Scaling laws for van der Waals interactions in nanostructured materials
venue: Nature communications
year: 2013

abstract: Based on first principles calculations, we have predicted an ultrathin metastable phosphorus nanotube as the smallest phosphorus nanotube and obtained a new class of two dimensional phosphorus allotropes via assembling the smallest phosphorus nanotubes into planar structures in different stacking orientations. These two dimensional phosphorene allotropes possess remarkable stabilities due to the strong inter tube van der Waals interactions, which cause an energy release of about 30 70 meV/atom depending on their stacking manners. Our results show that most of these two dimensional van der Waals phosphorene allotropes are energetically more favorable than the experimentally viable black alpha P and blue beta P. Three of them showing relatively higher probability to be synthesized in future are further confirmed to be dynamically stable semiconductors with strain tunable band gaps and remarkable piezoelectricity, which may have potential applications in nano sized sensors, piezotronics, and energy harvesting in portable electronic nano devices
author_names: Zhenqing Li

Chaoyu He

Tao Ouyang

Chunxiao Zhang

Caoxin Tang

Rudolf A Romer

Jianxin Zhong
title: New allotropes of phosphorene with remarkable stability and intrinsic piezoelectricity
year: 2017

abstract: Molecular orbital theory predicts that interactions between lone pair electrons give rise to van der Waals forces between layers due to the nonequivalent hybridization in bulk black phosphorus. First principles calculations show that phosphorene nanoribbons (PNRs) have a high activity and can be bonded easily with oxygen atoms and hydroxyl groups, indicating that the PNRs can be oxidized easily. The cliff PNR configuration can be maintained when it is passivated with hydroxyl groups, indicating that it could be stable in a strong alkaline environment. Upon oxidation of their zigzag, armchair, and cliff edges, phosphorene nanoribbons can be changed from semimetallic to semiconducting, and the band gap can be changed from direct to indirect. OHO (OH O) and OH (O H) passivated PNRs have intrinsic spin magnetic moments of approximately 2.00 mB, which originate from the edge unsaturation electrons and the symmetry reduction. Therefore, oxidized PNRs might have potential applications in photoelectro.
author_names: Bangfu Ding

Wei Chen

Zilong Tang

Junying Zhang
title: Tuning Phosphorene Nanoribbon Electronic Structure through Edge Oxidization
year: 2016