We study the stability and electronic properties of intrinsic point defects, vacancy and self-interstitial, in mono- and bi-layer phosphorene. We calculate the formation energies, quasiparticle defect states and charge transition levels (CTLs) of these defects using \textit{ab initio} density functional theory (DFT) and GW approximation to the electron self-energy. Using the DFT + GW two paths formalism for studying interstitial in monolayer phosphorene, we show that with the inclusion of electrostatic corrections CTLs can be calculated reliably. Our calculations show that all the native point defects have low formation energies 0.9-1.6 eV in neutral state. Furthermore, we find that vacancy in phosphorene behaves as an acceptor-like defect which can explain the p-type conductivity in phosphorene. On the other hand, interstitial can show both acceptor- and donor-like behaviour.
Using hybrid density functional theory combined with a semiempirical van der Waals dispersion correction, we have investigated the structural and electronic properties of vacancies and self-interstitials in defective few-layer phosphorene. We find that both a vacancy and a self-interstitial defect are more stable in the outer layer than in the inner layer. The formation energy and transition energy of both a vacancy and a self-interstitial P defect decrease with increasing film thickness, mainly due to the upward shift of the host valence band maximum in reference to the vacuum level. Conseque…
The two-dimensional semiconductor phosphorene has attracted extensive research interests for potential applications in optoelectronics, spintronics, catalysis, sensors, and energy conversion. To harness phosphorene's potential requires a better understanding of how intrinsic defects control carrier concentration, character, and mobility. Using density-functional theory and a charge correction scheme to account for the appropriate boundary conditions, we conduct a comprehensive study of the effect of structure on the formation energy, electronic structure, and charge transition level of the cha…
We have studied the electronic, magnetic and linear phonon dispersion behavior of Phosphorene monolayer using rst principle based ab initio method. Phosphorene monolayer is a semiconducting system with a dimensional dependent variable range of band gap. Vacancy has been done to study the geometry and physical behavior of the monolayer system. Pristine, vacancy induced monolayer and vacancy induced doped monolayer are included in the calculation. Dopant concentration has been well checked via optimization algorithm to maintain the dilute magnetic semiconducting behavior of the monolayer system.…
Using first-principles calculations, we study the electronic properties of few-layer phosphorene focusing on layer-dependent behavior of band gap, work function and band alignment and carrier effective mass. It is found that few-layer phosphorene shows a robust direct band gap character, and its band gap decreases with the number of layers following a power law. The work function decreases rapidly from monolayer (5.16 eV) to trilayer (4.56 eV), and then slowly upon further increasing the layer number. Compared to monolayer phosphorene, there is a drastic decrease of hole effective mass along t…
Low-dimensional materials synthesis based on phosphorus atoms is under intense study, and it is still one of the big challenges. Phosphorene, a monolayer of black phosphorus, is one of the most promising candidates for transistor and photonics devices at atomistic thickness. However, the lack of large-scale and defects-free growth significantly obstructs its device development. Here, we demonstrate the large-scale and defect-free phosphorene synthesis on Nickel (Ni) substrate. In addition, the effect of substrate orientation on the controllable synthesis of possible allotropes has also been de…
The surface potential and the efficiency of interfacial charge transfer are extremely important for designing future semiconductor devices based on the emerging two-dimensional (2D) phosphorene. Here, we directly measured the strongly layer-dependent surface potential of mono- and few-layer phosphorene on gold, which confirms with the reported theoretical prediction. At the same time, we used an optical way - photoluminescence (PL) spectroscopy to probe the charge transfer in phosphorene-gold hybrid system. We firstly observed highly anisotropic and layer-dependent PL quenching in the phosphor…
Recent reports on the fabrication of phosphorene, i.e., mono- or few-layer black phosphorus, have raised exciting prospects of an outstanding two-dimensional (2D) material that exhibits excellent properties for nanodevice applications. Here we study by first-principles calculations the adsorption of CO, CO2, NH3, NO and NO2 gas molecules on a mono-layer phosphorene. Our results predict superior sensing performance of phosphorene that rivals or even surpasses other 2D materials such as graphene and MoS2. We determine the optimal adsorption positions of these molecules on the phosphorene and ide…
We show that oxidation of phosphorene can lead to the formation of a new family of planar (2D) and tubular (1D) oxides and sub-oxides, most of them insulating. This confers to black phosphorus a native oxide that can be used as barrier material and protective layer. Further, the bandgap of phosphorene oxides depends on the oxygen concentration, suggesting that controlled oxidation can be used as a means to engineer the bandgap. For the oxygen saturated composition, P$_2$O$_5$, both the planar and tubular phases have a large bandgap energy of about 8.5eV, and are transparent in the near UV. The…
Phosphorene, an emerging elemental two-dimensional (2D) direct band gap semiconductor with fascinating structural and electronic properties distinctively different from other 2D materials such as graphene and MoS2, is promising for novel nanoelectronic and optoelectronic applications. Phonons, as one of the most important collective excitations, are at the heart for the device performance, as their interactions with electrons and photons govern the carrier mobility and light-emitting efficiency of the material. Here, through a detailed first-principles study, it is demonstrated that monolayer …
The capacity and stability of constituent electrodes determine the performance of Li-ion batteries. In this study, density functional theory is employed to explore the potential application of recently synthesized two dimensional phosphorene as electrode materials. Our results show that Li atoms can bind strongly with phosphorene monolayer and double layer with significant electron transfer. Besides, the structure of phosphorene is not much influenced by lithiation and the volume change is only 0.2\%. A semiconducting to metallic transition is observed after lithiation. The diffusion barrier i…
Phosphorene is a new two-dimensional material composed of a single or few atomic layers of black phosphorus. Phosphorene has both an intrinsic tunable direct band gap and high carrier mobility values, which make it suitable for a large variety of optical and electronic devices. However, the synthesis of single-layer phosphorene is a major challenge. The standard procedure to obtain phosphorene is by exfoliation. More recently, the epitaxial growth of single-layer phosphorene on Au(111) has been investigated by molecular beam epitaxy and the obtained structure has been described as a blue-phosp…
Defects are inevitably present in materials and always can affect their properties. Here, first-principles calculations are performed to systematically study the stability, structural and electronic properties of ten kinds of point defects in semiconducting phosphorene, including the Stone-Wales (SW-1 and SW-2) defect, single (SV59 and SV5566) and double vacancy (DV585-1, DV585-2, DV555777-1, DV555777-2, DV555777-3 and DV4104) defects. We find that these defects are all much easily created in phosphorene with higher areal density compared with graphene and silicene. They are easy distinguish e…
Density functional theory calculations have been carried out to investigate single-layer phosphorene functionalized with two kinds of organic molecules, i.e. an electrophilic molecule tetracyano-p-quinodimethane (TCNQ) as electron acceptor and a nucleophilic molecule tetrathia-fulvalene (TTF) as electron donor. The TCNQ molecule introduces shallow acceptor states in the gap of phosphorene close to the valence band edge (VBE), which makes the doped system a p-type semiconductor. However, when the TTF molecule is adsorbed on the phosphorene, the occupied molecular states introduced into the gap …
Recently fabricated two dimensional (2D) phosphorene crystal structures have demonstrated great potential in applications of electronics. Mechanical strain was demonstrated to be able to significantly modify the electronic properties of phosphorene and few-layer black phosphorus. In this work, we employed first principles density functional theory calculations to explore the mechanical properties of phosphorene, including ideal tensile strength and critical strain. It was found that a monolayer phosphorene can sustain tensile strain up to 27% and 30% in the zigzag and armchair directions, resp…
Phosphorene is emerging as a promising 2D semiconducting material with a direct band gap and high carrier mobility. In this paper, we examine the role of the extrinsic point defects including surface adatoms in modifying the electronic properties of phosphorene using density functional theory. The surface adatoms considered are B, C, N, O and F with a [He] core electronic configuration. Our calculations show that B and C, with electronegativity close to P, prefer to break the sp3 bonds of phosphorene, and reside at the interstitial sites in the 2D lattice by forming sp2 bonds with the native a…
Monolayer black and blue phosphorenes possess electronic and optical properties that result in unique features when the two materials are stacked. We devise a low-strain van-der-Waals double layer and investigate its properties with ab initio many-body perturbation theory techniques. A type-II band alignment and optical absorption in the visible range are found. The study demonstrates that spatially indirect excitons with full charge separation can be obtained between two layers with the same elemental composition but different crystalline structure, proving the system interesting for further …
Electronic properties of few-layer phosphorenes are investigated by the generalized tight-binding model. They are greatly diversified by the electric and magnetic fields ($E_z$ and $B_z$). The $E_z$-induced gap transition, Dirac cones, oscillatory bands and critical points are present in bilayer system, but absent in monolayer one. The diverse magnetic quantization phenomena cover the coexistent two subgroups of Landau levels, the uniform and non-uniform energy spacings, and the crossing and anti-crossing behaviors. Specifically, the wavefunctions exhibit the dramatic changes between the well-…
Using first-principles calculations, we have investigated the evolution of band-edges in few-layer phosphorene as a function of the number of P layers. Our results predict that monolayer phosphorene is an indirect band gap semiconductor and its valence band edge is extremely sensitive to strain. Its band gap could undergo an indirect-to-direct transition under a lattice expansion as small as 1% along zigzag direction. A semi-empirical interlayer coupling model is proposed, which can well reproduce the evolution of valence band-edges obtained by first-principles calculations. We conclude that t…
Based on {\em ab initio} density functional calculations, we propose $γ$-P and $δ$-P as two additional stable structural phases of layered phosphorus besides the layered $α$-P (black) and $β$-P (blue) phosphorus allotropes. Monolayers of some of these allotropes have a wide band gap, whereas others, including $γ$-P, show a metal-insulator transition caused by in-layer strain or changing the number of layers. An unforeseen benefit is the possibility to connect different structural phases at no energy cost. This becomes particularly valuable in assembling heterostructures with well-defined metal…
Due to the relatively low formation energies and highly mobile characteristics of atomic vacancies in phosphorene, understanding their evolutions becomes crucial for its structural integrity, chemical activities and applications. Herein, by combining first-principles calculations and kinetic Monte Carlo simulation, we investigate the time evolution and formation of atomic vacancy clusters from isolated monovacancies (MVs), aiming to uncover the mechanisms of diffusion, annihilation, reaction of these atomic vacancies. We find that while isolated MVs possess a highly mobile character, they reac…
Newly fabricated monolayer phosphorene and its few-layer structures are expected to be promising for electronic and optical applications because of their finite direct band gaps and sizable but anisotropic electronic mobility. By first-principles simulations, we show that this unique anisotropic conductance can be controlled by using simple strain conditions. With the appropriate biaxial or uniaxial strain, we can rotate the preferred conducting direction by 90 degrees. This will be of useful for exploring quantum Hall effects, and exotic electronic and mechanical applications based on phospho…
In this article, we explore the anisotropic electron energy loss spectrum (EELS) in monolayer phosphorene based on ab-initio time dependent density functional theory calculations. Similar to black phosphorous, the EELS of undoped monolayer phosphorene is characterized by anisotropic excitonic peaks for energies in vicinity of the bandgap, and by interband plasmon peaks for higher energies. On doping, an additional intraband plasmon peak also appears for energies within the bandgap. Similar to other two dimensional systems, the intraband plasmon peak disperses as $ω_{\rm pl} \propto \sqrt{q}$ i…
Bi2O2Se is an emerging semiconducting, air-stable layered material (Nat. Nanotechnol. 2017, 12, 530; Nano Lett. 2017, 17, 3021), potentially exceeding MoS2 and phosphorene in electron mobility and rivalling typical Van der Waals stacked layered materials in the next-generation high-speed and low-power electronics. Holding the promise of functional versatility, it is arousing rapidly growing interest from various disciplines, including optoelectronics, thermoelectronics and piezoelectronics. In this work, we comprehensively study the electrical properties of the native point defects in Bi2O2Se,…
In spite of great appeal of two-dimensional (2D) semiconductors for electronics and optoelectronics, to achieve required charge carrier concentrations by means of chemical doping remains a challenge, due to large defect ionization energies (IEs). Here by decomposing the defect IEs into the neutral single-electron defect level, the structural relaxation energy gain, and the electronic relaxation energy cost, we propose a conceptual picture that the large defect IEs are caused by two effects of reduced dimensionality. While the quantum confinement effect (QCE) makes the neutral single-electron p…
Phosphorene, a two-dimensional (2D) monolayer of black phosphorus, has attracted considerable theoretical interest, although the experimental realization of monolayer, bilayer, and few-layer flakes has been a significant challenge. Here we systematically survey conditions for liquid exfoliation to achieve the first large-scale production of monolayer, bilayer, and few-layer phosphorus, with exfoliation demonstrated at the 10-gram scale. We describe a rapid approach for quantifying the thickness of 2D phosphorus and show that monolayer and few-layer flakes produced by our approach are crystalli…
Atomically thin black phosphorus (BP) is a promising two-dimensional material for fabricating electronic and optoelectronic nano-devices with high mobility and tunable bandgap structures. However, the charge-carrier mobility in few-layer phosphorene (monolayer BP) is mainly limited by the presence of impurity and disorders. In this study, we demonstrate that vertical BP heterostructure devices offer great advantages in probing the electron states of monolayer and few-layer phosphorene at temperatures down to 2 K through capacitance spectroscopy. Electronic states in the conduction and valence …
Calculating the quasiparticle (QP) band structure of two-dimensional (2D) materials within the GW self-energy approximation has proven to be a rather demanding computational task. The main reason is the strong $\mathbf{q}$-dependence of the 2D dielectric function around $\mathbf{q} = \mathbf{0}$ that calls for a much denser sampling of the Brillouin zone than is necessary for similar 3D solids. Here we use an analytical expression for the small $\mathbf{q}$-limit of the 2D response function to perform the BZ integral over the critical region around $\mathbf{q} = \mathbf{0}$. This drastically r…
Phosphorene is a novel two-dimensional material that can be isolated through mechanical exfoliation from layered black phosphorus, but unlike graphene and silicene, monolayer phosphorene has a large band gap. It was thus unsuspected to exhibit band inversion and the ensuing topological insulator behavior. It has recently attracted interest because of its proposed application as field effect transistors. Using first-principles calculations with applied perpendicular electric field F we predict a continuous transition from the normal insulator to a topological insulator and eventually to a metal…
