Phosphorene

/Tag: Phosphorene

Controlled Synthesis of 2D Palladium Diselenide for Sensitive Photodetector Applications

2018-11-17T22:32:13+00:00November 17th, 2018|Categories: Publications|Tags: |

This study reports on the wafer‐area synthesis of high‐quality 2D PdSe2 layer through a simple selenization method. Both experimental analysis and theoretical simulation reveal that the PdSe2 film exhibits a gradual transition from a semiconductor (monolayer) to semimetal (bulk). Further combination of PdSe2 with Si leads to a fast and sensitive broadband photodiode, with a high responsivity and specific detectivity. Abstract Palladium diselenide (PdSe2), a thus far scarcely studied group‐10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer‐scale and homogeneous 2D PdSe2 film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe2 with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe2 exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe2 layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W−1) and specific detectivity (≈1013 Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the as‐selenized PdSe2 is a promising material for optoelectronic application.

Published in: "Advanced Functional Materials".

Controlled Synthesis of 2D Palladium Diselenide for Sensitive Photodetector Applications

2018-11-16T04:33:48+00:00November 16th, 2018|Categories: Publications|Tags: |

This study reports on the wafer‐area synthesis of high‐quality 2D PdSe2 layer through a simple selenization method. Both experimental analysis and theoretical simulation reveal that the PdSe2 film exhibits a gradual transition from a semiconductor (monolayer) to semimetal (bulk). Further combination of PdSe2 with Si leads to a fast and sensitive broadband photodiode, with a high responsivity and specific detectivity. Abstract Palladium diselenide (PdSe2), a thus far scarcely studied group‐10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer‐scale and homogeneous 2D PdSe2 film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe2 with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe2 exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe2 layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W−1) and specific detectivity (≈1013 Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the as‐selenized PdSe2 is a promising material for optoelectronic application.

Published in: "Advanced Functional Materials".

On the influence of dilute charged impurity and perpendicular electric field on the electronic phase of phosphorene: Band gap engineering

2018-11-13T12:33:20+00:00November 13th, 2018|Categories: Publications|Tags: |

Tuning the band gap plays an important role for applicability of 2D materials in the semiconductor industry. The present paper is a theoretical study on the band gap engineering using the electronic density of states (DOS) of phosphorene in the presence of dilute charged impurity and of a perpendicular electric field. The electronic DOS is numerically calculated using a combination of the continuum model Hamiltonian and the Green’s function approach. Our findings show that the band gap of phosphorene in the absence and presence of the perpendicular electric field decreases with increasing impurity concentration and/or impurity scattering potential. Further, we found that in the presence of opposite perpendicular electric fields, the electronic DOS of disordered phosphorene shows different changing behaviors stemming from the Stark effect: in the positive case the band gap increases with increasing electric-field strength; whereas in the negative case the band gap disappears. The…

Published in: "EPL".

Ultrafast photocarrier recombination dynamics in black phosphorus-molybdenum disulfide (BP/MoS2) heterostructure. (arXiv:1811.04706v1 [cond-mat.mes-hall])

2018-11-13T04:30:17+00:00November 13th, 2018|Categories: Publications|Tags: , , , |

Van der Waals (vdW) heterostructures constructed with two-dimensional (2D) materials have attracted great interests, due to their fascinating properties and potential for novel applications. While earlier efforts have advanced the understanding of the ultrafast cross-layer charge transfer process in 2D heterostructures, mechanisms for the interfacial photocarrier recombination remain, to a large extent, unclear. Here, we investigate a heterostructure comprised of black phosphorus (BP) and molybdenum disulfide (MoS2), with a type-II band alignment. Interestingly, it is found that the photo-generated electrons in MoS2 (transferred from BP) exhibit an ultrafast lifetime of about 5 ps, significantly shorter than those of the constituent materials. By corroborating with the relaxation of photo-excited holes in BP, it is revealed that the ultrafast time constant is as a result of efficient Langevin recombination, where the high hole mobility of BP facilitates a large recombination coefficient (approximately 2×10^-10 m^2/s). In addition, broadband transient absorption spectroscopy confirms that the hot electrons transferred to MoS2 distribute over a broad energy range following an ultrafast thermalization. The rate of the interlayer Langevin recombination is found to exhibit no energy level dependence. Our findings provide essential insights into the fundamental photo-physics in type-II 2D heterostructures, and also provide useful guidelines for customizing photocarrier lifetimes of BP for high-speed photo-sensitive devices.

Published : "arXiv Mesoscale and Nanoscale Physics".

Low Lattice Thermal Conductivity of a Two-Dimensional Phosphorene Oxide. (arXiv:1811.04612v1 [cond-mat.mtrl-sci])

2018-11-13T02:29:25+00:00November 13th, 2018|Categories: Publications|Tags: |

A fundamental understanding of the phonon transport mechanism is important for optimizing the efficiency of thermoelectric devices. In this study, we investigate the thermal transport properties of the oxidized form of phosphorene called phosphorene oxide (PO) by solving phonon Boltzmann transport equation based on first-principles density functional theory. We reveal that PO exhibits a much lower thermal conductivity (2.42-7.08 W/mK, at 300 K) than its pristine counterpart as well as other two-dimensional materials. To comprehend the physical origin of such low thermal conductivity, we scrutinize the contribution of each phonon branch to the thermal conductivity by evaluating various mode-dependent quantities including Gruneisen parameters, anharmonic threep-honon scattering rate, phase space of three-phonon scattering processes. Our results show that its exible puckered structure of PO leads to smaller sound velocities; its broken-mirror symmetry allows more ZA phonon scattering; and the relatively-free vibration of dangling oxygen atoms in PO gives rise to additional scattering resulting in further reduction in the phonon lifetime. These results can be verified by the fact that PO has larger phase space for three-phonon processes than phosphorene. Furthermore we show that the thermal conductivity of PO can be optimized by controlling its size or its phonon mean free path, indicating that PO can be a promising candidate for low-dimensional thermoelectric devices.

Published in: "arXiv Material Science".

Liquid-exfoliation of S-doped black phosphorus nanosheets for enhanced oxygen evolution catalysis

2018-11-12T18:33:03+00:00November 12th, 2018|Categories: Publications|Tags: |

Black phosphorus (BP) has recently drawn great attention in the field of electrocatalysis due to its distinct electrocatalytic activity for the oxygen evolution reaction (OER). However, the slow OER kinetics and the poor environmental stability of BP seriously limits its overall OER performance and prevents its electrocatalysis application. Here, sulfur (S)-doped BP nanosheets, which are prepared using high-pressure synthesis followed by liquid exfoliation, have been demonstrated to have much better OER electrocatalytic activity and environmental stability compared to their undoped counterparts. The S-doped BP nanosheets display a Tafel slope of 75 mV dec −1 , which is a favorable value refered to the kinetics of OER in electrochemical tests. Notably, there is no degradation of S-doped BP nanosheets after six days exposure to ambient, indicating an excellent environmental stability of the S-doped BP. The density functional theory calculations show that the OER activity …

Published in: "Nanotechnology".

Promise and Challenge of Phosphorus in Science, Technology, and Application

2018-11-11T04:33:02+00:00November 11th, 2018|Categories: Publications|Tags: , |

The synthesis, properties, functionalization, and applications of phosphorus are reviewed to reveal the challenges and opportunities facing present and future research on phosphorus‐based functional materials. The topological constructions of various phosphorus‐based functional materials are an encouraging prospect in the rapid development of nanotechnology. Abstract Tremendous progress has been made in scientific research and application of phosphorus allotropes and their hybrid materials in recent decades. In particular, nanomaterial design has emerged as a promising solution to tackle many fundamental problems in conventional materials. This review discusses phosphorus‐based functional materials from the perspective of topological structures, which have several advantages such as good chemical stability, high surface areas, adjustable particle sizes and compositions, as well as various functionalities that enable a good performance in energy storage and conversion as well as other applications. Then, the progress on these functional materials for application in batteries, supercapacitors, catalysis, field‐effect transistors, optoelectronics, flexible electronics, sensors, biomedicine, etc., is discussed and summarized as well. Special attention is given to the research efforts to overcome the inherent shortcomings faced by red/black phosphorus. The aim is to elucidate the relationship between the phosphorus‐based topological structures and their performance. Finally, this review casts an insightful outlook on the future direction of the phosphorus‐based materials in nanotechnology.

Published in: "Advanced Functional Materials".

Polymer Ionic Liquid Stabilized Black Phosphorus for Environmental Robust Flexible Optoelectronics

2018-11-11T04:32:27+00:00November 11th, 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".

Fraunhofer response and supercurrent spin switching in black phosphorus with strain and disorder

2018-11-09T18:35:33+00:00November 9th, 2018|Categories: Publications|Tags: |

Author(s): Mohammad Alidoust, Morten Willatzen, and Antti-Pekka JauhoWe develop theory models for both ballistic and disordered superconducting monolayer 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 quasic…[Phys. Rev. B 98, 184505] Published Fri Nov 09, 2018

Published in: "Physical Review B".

Optical absorption properties of few-layer phosphorene

2018-11-09T18:35:27+00:00November 9th, 2018|Categories: Publications|Tags: |

Author(s): Zahra Torbatian and Reza AsgariWe 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 conduct…[Phys. Rev. B 98, 205407] Published Fri Nov 09, 2018

Published in: "Physical Review B".

Rectifying properties in 90{deg} rotated bilayer black phosphorus nanojunction: A first principle study. (arXiv:1811.03523v1 [physics.app-ph])

2018-11-09T04:30:38+00:00November 9th, 2018|Categories: Publications|Tags: , |

We explore the possibility of using van dar Waals bonded heterostructures of stacked together 2D bilayer black phosphorus (BP) for nanoscale device applications. The electronic property of BP in AA stacking and 90{deg} twisted is studied with density functional theory. Further, we study the homogeneous nanojunction architecture of BP to use its anisotropic properties. Using the first principle simulations along with NEGF approach, we calculate quantum transport properties of the nanojunction setup. The interlayer directionally dependent current characteristics are explained in different setups. Our result revealed that 90{deg} twisted nanojucntion device would be a potential rectifier despite having no p-n junction characteristic only due to the intrinsic anisotropy of the material, making tunneling between armchair- and zigzag-directional BP sheets asymmetric.

Published : "arXiv Mesoscale and Nanoscale Physics".

Epitaxial Synthesis of Blue Phosphorene

2018-11-07T08:35:28+00:00November 7th, 2018|Categories: Publications|Tags: |

Phosphorene is a 2D material with an intrinsic tunable bandgap and high carrier mobility. Epitaxial growth of single‐layer phosphorene on Au(111) is achieved using molecular beam epitaxy. Scanning tunneling microscope images show high‐quality and ordered monolayer phosphorene. Density functional theory calculations support a blue phosphorene layer presenting two different structures. Photoemission (ARPES) measurements reveal a bandgap of at least 0.8 eV. Abstract Phosphorene is a new 2D material composed of a single or few atomic layers of black phosphorus. Phosphorene has both an intrinsic tunable direct bandgap 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) was investigated by molecular beam epitaxy and the obtained structure described as a blue phosphorene sheet. In the present study, large areas of high‐quality monolayer phosphorene, with a bandgap value equal to at least 0.8 eV, are synthesized on Au(111). The experimental investigations, coupled with density functional theory calculations, give evidence of two distinct phases of blue phosphorene on Au(111), instead of one as previously reported, and their atomic structures are determined.

Published in: "Small".

Charge Density Waves Driven by Peierls Instability at the Interface of Two‐Dimensional Lateral Heterostructures

2018-11-07T08:35:22+00:00November 7th, 2018|Categories: Publications|Tags: , , , , |

Charge density wave (CDW) formation at the one‐dimensional interface embedded in a lateral two‐dimensional (2D) heterostructure comprising blue and black phosphorene is found. The CDW formation is driven by the Peierls instability and substantially modifies the band alignment of the heterostructure. These findings are applicable to other 2D lateral heterostructures and have important implications for their application. Abstract The origin of charge density wave (CDW) observed in low‐dimensional systems is, for long, a subject of intensive debate in contemporary condensed matter physics. Specifically, a simple and well established model, namely, the Peierls instability is often (but not always) used to clearly explain CDW states in real systems. Here, first‐principles density functional theory calculations are used to show CDW formation at a one‐dimensional interface embedded in a lateral heterostructure comprising blue and black phosphorene, even at room temperature. The CDW formation is fully explained by the Peierls mechanism, including a double‐periodicity lattice distortion energy lowering and a bandgap opening. The lattice distortion also substantially modifies the band alignment of the heterostructure. Comparison with a freestanding P chain shows that the structural distortion is confined to one dimension within the heterostructures, ruling out competing non‐Peierls‐type distortions in two dimensions. In addition, similar Peierls‐type distortions for other lateral heterostructures are shown by using the example of a graphene–hexagonal boron nitride heterostructure, which may stimulate related studies in different 2D systems. These findings not only shed more light on the Peierls mechanism, but also have important implications for devices based on 2D lateral

Published in: "Small".

Promise and Challenge of Phosphorus in Science, Technology, and Application

2018-11-07T02:33:28+00:00November 7th, 2018|Categories: Publications|Tags: , |

The synthesis, properties, functionalization, and applications of phosphorus are reviewed to reveal the challenges and opportunities facing present and future research on phosphorus‐based functional materials. The topological constructions of various phosphorus‐based functional materials are an encouraging prospect in the rapid development of nanotechnology. Abstract Tremendous progress has been made in scientific research and application of phosphorus allotropes and their hybrid materials in recent decades. In particular, nanomaterial design has emerged as a promising solution to tackle many fundamental problems in conventional materials. This review discusses phosphorus‐based functional materials from the perspective of topological structures, which have several advantages such as good chemical stability, high surface areas, adjustable particle sizes and compositions, as well as various functionalities that enable a good performance in energy storage and conversion as well as other applications. Then, the progress on these functional materials for application in batteries, supercapacitors, catalysis, field‐effect transistors, optoelectronics, flexible electronics, sensors, biomedicine, etc., is discussed and summarized as well. Special attention is given to the research efforts to overcome the inherent shortcomings faced by red/black phosphorus. The aim is to elucidate the relationship between the phosphorus‐based topological structures and their performance. Finally, this review casts an insightful outlook on the future direction of the phosphorus‐based materials in nanotechnology.

Published in: "Advanced Functional Materials".

Charge Density Waves Driven by Peierls Instability at the Interface of Two‐Dimensional Lateral Heterostructures

2018-11-07T00:34:10+00:00November 6th, 2018|Categories: Publications|Tags: , , , , |

Charge density wave (CDW) formation at the one‐dimensional interface embedded in a lateral two‐dimensional (2D) heterostructure comprising blue and black phosphorene is found. The CDW formation is driven by the Peierls instability and substantially modifies the band alignment of the heterostructure. These findings are applicable to other 2D lateral heterostructures and have important implications for their application. Abstract The origin of charge density wave (CDW) observed in low‐dimensional systems is, for long, a subject of intensive debate in contemporary condensed matter physics. Specifically, a simple and well established model, namely, the Peierls instability is often (but not always) used to clearly explain CDW states in real systems. Here, first‐principles density functional theory calculations are used to show CDW formation at a one‐dimensional interface embedded in a lateral heterostructure comprising blue and black phosphorene, even at room temperature. The CDW formation is fully explained by the Peierls mechanism, including a double‐periodicity lattice distortion energy lowering and a bandgap opening. The lattice distortion also substantially modifies the band alignment of the heterostructure. Comparison with a freestanding P chain shows that the structural distortion is confined to one dimension within the heterostructures, ruling out competing non‐Peierls‐type distortions in two dimensions. In addition, similar Peierls‐type distortions for other lateral heterostructures are shown by using the example of a graphene–hexagonal boron nitride heterostructure, which may stimulate related studies in different 2D systems. These findings not only shed more light on the Peierls mechanism, but also have important implications for devices based on 2D lateral

Published in: "Small".

Promise and Challenge of Phosphorus in Science, Technology, and Application

2018-11-07T00:32:54+00:00November 6th, 2018|Categories: Publications|Tags: , |

The synthesis, properties, functionalization, and applications of phosphorus are reviewed to reveal the challenges and opportunities facing present and future research on phosphorus‐based functional materials. The topological constructions of various phosphorus‐based functional materials are an encouraging prospect in the rapid development of nanotechnology. Abstract Tremendous progress has been made in scientific research and application of phosphorus allotropes and their hybrid materials in recent decades. In particular, nanomaterial design has emerged as a promising solution to tackle many fundamental problems in conventional materials. This review discusses phosphorus‐based functional materials from the perspective of topological structures, which have several advantages such as good chemical stability, high surface areas, adjustable particle sizes and compositions, as well as various functionalities that enable a good performance in energy storage and conversion as well as other applications. Then, the progress on these functional materials for application in batteries, supercapacitors, catalysis, field‐effect transistors, optoelectronics, flexible electronics, sensors, biomedicine, etc., is discussed and summarized as well. Special attention is given to the research efforts to overcome the inherent shortcomings faced by red/black phosphorus. The aim is to elucidate the relationship between the phosphorus‐based topological structures and their performance. Finally, this review casts an insightful outlook on the future direction of the phosphorus‐based materials in nanotechnology.

Published in: "Advanced Functional Materials".

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".

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