/Tag: Phosphorene

Polymer Ionic Liquid Stabilized Black Phosphorus for Environmental Robust Flexible Optoelectronics

2018-11-07T00:32:09+00:00November 6th, 2018|Categories: Publications|Tags: |

An efficient strategy to fabricate polymer ionic liquid (PIL)‐passivated 2D BP is developed. The PIL‐modified 2D BP shows negligible structural deterioration in 100 d under ambient condition. Photodetectors based on PIL‐modified 2D BP exhibit good performance and excellent stability. Abstract Black phosphorus (BP) has attracted great attentions in the last few years, but their applications in optoelectronics have been strongly hindered by the poor environmental stability, especially under light irradiation. Herein, the fabrication of surface passivated few‐layer BP assisted by polymer ionic liquids (PILs) is reported. The PIL‐modified 2D BP exhibits excellent stability under ambient conditions, with negligible deterioration in 100 d. Furthermore, the PILs attached on the BP surface provide reliable and flexible electrical contact between the few‐layer BP and other device components. As a proof of concept, PIL‐modified BP nanosheets are successfully applied in flexible photodetectors, which show high flexibility, good detectivity with no obvious performance deterioration in 120 h. This work demonstrates that the PIL modification can endow BP nanosheets with excellent environmental stability and good conductivity, so that may significantly expand the applications of BP in flexible optoelectronics.

Published in: "Advanced Functional Materials".

Epitaxial Synthesis of Blue Phosphorene. (arXiv:1811.01289v1 [cond-mat.mtrl-sci])

2018-11-06T05:29:36+00:00November 6th, 2018|Categories: Publications|Tags: |

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-phosphorene sheet. In the present study, large areas of high-quality monolayer phosphorene, with a band gap value at least equal to 0.8 eV, have been synthesized on Au(111). Our experimental investigations, coupled with DFT calculations, give evidence of two distinct phases of blue phosphorene on Au(111), instead of one as previously reported, and their atomic structures have been determined.

Published in: "arXiv Material Science".

Optical absorption properties of few-layer phosphorene. (arXiv:1811.01172v1 [cond-mat.mes-hall])

2018-11-06T04:30:29+00:00November 6th, 2018|Categories: Publications|Tags: , , , |

We investigate the optical absorption and transmission of few-layer phosphorene in the framework of ab initio density functional simulations and many-body perturbation theory at the level of random phase approximation. In bilayer phosphorene, the optical transition of the valence band to the conduction band appears along the armchair direction at about 0.72 eV, while it is absent along the zigzag direction. This phenomenon is consistent with experimental observations. The angle-resolved optical absorption in few-layer phosphorene shows that it is transparent when illuminated by near grazing incidence of light. Also, there is a general trend of an increase in the absorption by increasing the number of layers. Our results show that the bilayer phosphorene exhibits greater absorbance compared to that of bilayer graphene in the ultraviolet region. Moreover, the maximal peak in the calculated absorption of bilayer MoS2 is in the visible region, while bilayer graphene and phosphorene are transparent. Besides, the collective electronic excitations of few-layer phosphorene are explored. An optical mode (in-phase mode) that follows a low-energy sqrt q dependence for all structures, and another which is a damped acoustic mode (out-of-phase mode) with linear dispersion for multilayer phosphorene are obtained. The anisotropy of the band structure of few-layer phosphorene along the armchair and zigzag directions is manifested in the collective plasmon excitations.

Published : "arXiv Mesoscale and Nanoscale Physics".

Exchange interaction of magnetic impurities in a biased bilayer phosphorene nanoribbon

2018-11-02T16:34:12+00:00November 2nd, 2018|Categories: Publications|Tags: |

Author(s): Moslem Zare and Ebrahim SadeghiWe study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between local magnetic moments in zigzag bilayer phosphorene nanoribbons (ZBLPNRs) under a perpendicular electric field. We evaluate the spatial and electric field dependency of the static spin susceptibility in real space in various conf…[Phys. Rev. B 98, 205401] Published Fri Nov 02, 2018

Published in: "Physical Review B".

Fraunhofer response and supercurrent spin-switching in Black Phosphorus with strain and impurity. (arXiv:1811.00027v1 [cond-mat.mtrl-sci])

2018-11-02T02:29:23+00:00November 2nd, 2018|Categories: Publications|Tags: |

We develop theory models for both ballistic and disordered superconducting black phosphorus devices in the presence of magnetic exchange field and stress. The ballistic case is studied through a microscopic Bogoliubov-de Gennes formalism while for the disordered case we formulate a quasiclassical model. Utilizing the two models, we theoretically study the response of supercurrent to an externally applied magnetic field in two-dimensional black phosphorus Josephson junctions. Our results demonstrate that the response of the supercurrent to a perpendicular magnetic field in ballistic samples can deviate from the standard Fraunhofer interference pattern when the Fermi level and mechanical stress are varied. This finding suggests the combination of chemical potential and strain as an efficient external knob to control the current response in high-sensitive strain-effect transistors and SQUIDs. We also study the supercurrent in a superconductor-ferromagnet-ferromagnet-superconductor junction where the magnetizations of the two adjacent magnetized regions are uniform with misaligned orientations. We show that the magnetization misalignment can control the excitation of higher harmonics than the first harmonic $sin varphi$ (in which $varphi$ is the phase difference between the superconductors) in supercurrent and constitutes a full spin switching current element. Finally, we discuss possible experimental implementations of our findings. We foresee our models and discussions can provide guidelines to experimentalists in designing devices and future investigations.

Published in: "arXiv Material Science".

Mass spectrometry imaging of the in situ drug release from nanocarriers

2018-11-01T02:36:30+00:00November 1st, 2018|Categories: Publications|Tags: , |

It is crucial but of a great challenge to study in vivo and in situ drug release of nanocarriers when developing a nanomaterial-based drug delivery platform. We developed a new label-free laser desorption/ionization mass spectrometry (MS) imaging strategy that enabled visualization and quantification of the in situ drug release in

Published in: "Science Advances".

Generating strong room-temperature photoluminescence in black phosphorus using organic molecules

2018-10-30T12:39:51+00:00October 30th, 2018|Categories: Publications|Tags: |

Black phosphorus (BP) exhibits fascinating thickness dependent optical and electronic characteristics. However, photoluminescence (PL) emission in the visible spectrum does not exist for multilayer BP and requires the achievement of single layer, which are highly environmentally sensitive. This poses significant challenges in realizing the true potential of BP as multilayer BP exhibits exciting optical properties for a range of applications. Here, for the first time we reveal visible range room-temperature photoluminescence (PL) in multi-layered black phosphorus (BP) via chemical doping using organic molecules. We find the drastic enhancement of PL originates from the adsorption of p-type dopants and offer further insight using density functional theory (DFT) calculations. The reported non-destructive method creates a pathway to precisely control optical and electronic properties thereby expanding the application horizon for multilayer BP that is environmentally robust compared …

Published in: "2DMaterials".

Exciton in phosphorene: Strain, impurity, thickness and heterostructure. (arXiv:1810.11994v1 [cond-mat.mes-hall])

2018-10-30T04:30:32+00:00October 30th, 2018|Categories: Publications|Tags: , |

Reduced electron screening in two-dimension plays a fundamental role in determining exciton properties, which dictates optoelectronic and photonic device performances. Considering the explicit electron-hole interaction within the $GW-$Bethe-Salpeter formalism, we first study the excitonic properties of pristine phosphorene and investigate the effects of strain and impurity coverage. The calculations reveal strongly bound exciton in these systems with anisotropic spatial delocalization. Further, we present a simplified hydrogenic model with anisotropic exciton mass and effective electron screening as parameters, and the corresponding results are in excellent agreement with the present $GW-$BSE calculations. The simplified model is then used to investigate exciton renormalization in few-layer and heterostructure phosphorene. The changes in carrier effective mass along with increasing electron screening renormalizes the exciton binding in these systems. We establish that the present model, where the parameters are calculated within computationally less expensive first-principles calculations, can predict exciton properties with excellent accuracy for larger two-dimensional systems, where the many-body $GW-$BSE calculations are impossible.

Published : "arXiv Mesoscale and Nanoscale Physics".

Tunable transmission due to defects in zigzag phosphorene nanoribbons. (arXiv:1810.11827v1 [cond-mat.mtrl-sci])

2018-10-30T02:29:24+00:00October 30th, 2018|Categories: Publications|Tags: , |

Transport of the edge-state electrons along zigzag phosphorene nanoribbons in presence of two impurities/vacancies is analytically investigated. Considering the places of the defects, a number of different situations are examined. When both defects are placed on the edge zigzag chain, as is expected, with changing the energy of the traveling electrons the electrical conductance exhibits a resonance behavior. In this case, for two vacancies the observed resonant peaks become extremely sharp. An amazing behavior is seen when the second vacancy is located along an armchair chain while the first is placed at the intersection of the edge zigzag and this armchair chains. In this case, in a considerable range of energy, the conductance is strongly strengthened. In fact the presence of the second vacancy create a shielded region around the first vacancy, consequently, the traveling wave bypasses this region and enhances the conductivity. The analytical results are compared with numerical simulations showing a very good agreement.

Published in: "arXiv Material Science".

High-Quality Reconfigurable Black Phosphorus p-n Junctions

2018-10-23T00:32:37+00:00October 23rd, 2018|Categories: Publications|Tags: , , , , |

The p-n junction is the fundamental building block for electronics and photonics applications. In a conventional p-n junction, the performance parameters cannot be tuned due to the fixed doping level after ion implantation. In this paper, reconfigurable p-n or n-p junctions were built based on the ambipolar black phosphorus (BP) and other 2-D materials, namely, graphene and hexagonal boron nitride (h-BN). High-quality graphene/h-BN/BP/h-BN sandwich device was created by the dry transfer method in an inert environment. Graphene serves as the local back gate, which can tune BP partially into either n-type or p-type material. The rest of the BP channel can be controlled by the back gate. The BP encapsulated device can enable the high performance of the ideality factor down to 1.08 (p-n junction) and 1.18 (n-p junction). The device developed in this paper has a more balanced ideality factor than previously reported reconfigurable WSe2 and BP devices. By tuning the back gate and graphene gate, the BP device can be tuned into four operational quadrants, namely, n-n, n-p, p-n, and p-p junctions. Moreover, the hole mobility of BP is up to 404 cm2/$text {V}cdot text {s}$ at room temperature. Our work shows that the BP heterostructure is very promising for high-speed reconfigurable logic functions and circuits.

Published in: "IEEE Transactions on Electron Devices".

STM study of exfoliated few layer black phosphorus annealed in ultrahigh vacuum

2018-10-22T16:34:15+00:00October 22nd, 2018|Categories: Publications|Tags: |

Black phosphorus (bP) has emerged as an interesting addition to the category of two-dimensional materials. Surface-science studies on this material are of great interest, but they are hampered by bP’s high reactivity to oxygen and water, a major challenge to scanning tunneling microscopy (STM) experiments. As a consequence, the large majority of these studies were performed by cleaving a bulk crystal in situ . Here we present a study of surface modifications on exfoliated bP flakes upon consecutive annealing steps, up to 550 °C, well above the sublimation temperature of bP. In particular, our attention is focused on the temperature range 375 °C–400 °C, when sublimation starts, and a controlled desorption from the surface occurs alongside with the formation of characteristic well-aligned craters. There is an open debate in the literature about the crystallographic orientation of these craters, whether they align along the zigzag or the armchair direction. Thanks to the atom…

Published in: "2DMaterials".

Theranostic nanocomposite from upconversion luminescent nanoparticles and black phosphorus nanosheets

2018-10-19T10:32:35+00:00October 19th, 2018|Categories: Publications|Tags: |

RSC Adv., 2018, 8,35706-35718DOI: 10.1039/C8RA07441K, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.Solomon Tiruneh Dibaba, Ruoyan Wei, Wensong Xi, Lei Zhao, Liyi Shi, Wei Ren, Torsten Mayr, Lining SunWe successfully synthesized a multifunctional theranostic nanocomposite

Published in: "RSC Advances".

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