The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
A Castro H Neto - One of the best experts on this subject based on the ideXlab platform.
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surface transfer doping induced effective modulation on ambipolar characteristics of few layer Black Phosphorus
Nature Communications, 2015Co-Authors: Du Xiang, A Castro H Neto, Jiadan Lin, Barbaros Ozyilmaz, Cheng Han, Shu Zhong, Yiyang Liu, Xueao Zhang, A T S Wee, Wei ChenAbstract:Black Phosphorus, a fast emerging two-dimensional material, has been configured as field effect transistors, showing a hole-transport-dominated ambipolar characteristic. Here we report an effective modulation on ambipolar characteristics of few-layer Black Phosphorus transistors through in situ surface functionalization with caesium carbonate (Cs2CO3) and molybdenum trioxide (MoO3), respectively. Cs2CO3 is found to strongly electron dope Black Phosphorus. The electron mobility of Black Phosphorus is significantly enhanced to similar to 27 cm(2)V(-1) s(-1) after 10 nm Cs2CO3 modification, indicating a greatly improved electron-transport behaviour. In contrast, MoO3 decoration demonstrates a giant hole-doping effect. In situ photoelectron spectroscopy characterization reveals significant surface charge transfer occurring at the dopants/Black Phosphorus interfaces. Moreover, the surface-doped Black Phosphorus devices exhibit a largely enhanced photodetection behaviour. Our findings coupled with the tunable nature of the surface transfer doping scheme ensure Black Phosphorus as a promising candidate for further complementary logic electronics.
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tunable optical properties of multilayer Black Phosphorus thin films
Physical Review B, 2014Co-Authors: A S Rodin, Yongjin Jiang, Han Wang, A Castro H Neto, A CarvalhoAbstract:Black Phosphorus thin films might offer attractive alternatives to narrow gap compound semiconductors for optoelectronics across mid- to near-infrared frequencies. In this work, we calculate the optical conductivity tensor of multilayer Black Phosphorus thin films using the Kubo formula within an effective low-energy Hamiltonian. The optical absorption spectra of multilayer Black Phosphorus are shown to vary sensitively with thickness, doping, and light polarization. In conjunction with experimental spectra obtained from infrared absorption spectroscopy, we also discuss the role of interband coupling and disorder on the observed anisotropic absorption spectra.
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strain induced gap modification in Black Phosphorus
Physical Review Letters, 2014Co-Authors: A S Rodin, A Castro H Neto, A CarvalhoAbstract:The band structure of single-layer Black Phosphorus and the effect of strain are predicted using density functional theory and tight-binding models. Having determined the localized orbital composition of the individual bands from first principles, we use the system symmetry to write down the effective low-energy Hamiltonian at the Γ point. From numerical calculations and arguments based on the crystal structure of the material, we show that the deformation in the direction normal to the plane can be used to change the gap size and induce a semiconductor-metal transition.
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tunable optical properties of multilayers Black Phosphorus
2014Co-Authors: Tony Low, A S Rodin, A F Carvalho, Yongjin Jiang, Han Wang, Fengnian Xia, A Castro H NetoAbstract:Black Phosphorus thin films might offer attractive alternatives to narrow gap compound semiconductors for optoelectronics across mid- to near-infrared frequencies. In this work, we calculate the optical conductivity tensor of multilayer Black Phosphorus thin films using the Kubo formula within an effective low-energy Hamiltonian. The optical absorption spectra of multilayer Black Phosphorus are shown to vary sensitively with thickness, doping, and light polarization. In conjunction with experimental spectra obtained from infrared absorption spectroscopy, we also discuss the role of interband coupling and disorder on the observed anisotropic absorption spectra.
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electric field effect in ultrathin Black Phosphorus
Applied Physics Letters, 2014Co-Authors: Steven P Koenig, A Castro H Neto, Rostislav A Doganov, Hennrik Schmidt, Barbaros OzyilmazAbstract:Black Phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer Black Phosphorus field effect devices on Si/SiO2 and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm2/Vs and drain current modulation of over 103. At low temperatures, the on-off ratio exceeds 105, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin Black Phosphorus crystals over the course of 1 h after exfoliation.
Peide D Ye - One of the best experts on this subject based on the ideXlab platform.
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auxetic Black Phosphorus a 2d material with negative poisson s ratio
Nano Letters, 2016Co-Authors: Yuchen Du, Xianfan Xu, Jesse Maassen, Wangran Wu, Peide D YeAbstract:The Poisson’s ratio of a material characterizes its response to uniaxial strain. Materials normally possess a positive Poisson’s ratio - they contract laterally when stretched, and expand laterally when compressed. A negative Poisson’s ratio is theoretically permissible but has not, with few exceptions of man-made bulk structures, been experimentally observed in any natural materials. Here, we show that the negative Poisson’s ratio exists in the low-dimensional natural material Black Phosphorus and that our experimental observations are consistent with first-principles simulations. Through applying uniaxial strain along armchair direction, we have succeeded in demonstrating a cross-plane interlayer negative Poisson’s ratio on Black Phosphorus for the first time. Meanwhile, our results support the existence of a cross-plane intralayer negative Poisson’s ratio in the constituent phosphorene layers under uniaxial deformation along the zigzag axis, which is in line with a previous theoretical prediction. The ...
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semiconducting Black Phosphorus synthesis transport properties and electronic applications
Chemical Society Reviews, 2015Co-Authors: Han Liu, Yexin Deng, Yuchen Du, Peide D YeAbstract:Phosphorus is one of the most abundant elements preserved in earth, and it comprises a fraction of ∼0.1% of the earth crust. In general, Phosphorus has several allotropes, and the two most commonly seen allotropes, i.e. white and red Phosphorus, are widely used in explosives and safety matches. In addition, Black Phosphorus, though rarely mentioned, is a layered semiconductor and has great potential in optical and electronic applications. Remarkably, this layered material can be reduced to one single atomic layer in the vertical direction owing to the van der Waals structure, and is known as phosphorene, in which the physical properties can be tremendously different from its bulk counterpart. In this review article, we trace back to the research history on Black Phosphorus of over 100 years from the synthesis to material properties, and extend the topic from Black Phosphorus to phosphorene. The physical and transport properties are highlighted for further applications in electronic and optoelectronics devices.
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Black Phosphorus monolayer mos2 van der waals heterojunction p n diode
ACS Nano, 2014Co-Authors: Yexin Deng, Nathan J. Conrad, Sina Najmaei, Xianfan Xu, Pulickel Madhavapanicker Ajayan, Yongji Gong, Peide D YeAbstract:Phosphorene, a elemental 2D material, which is the monolayer of Black Phosphorus, has been mechanically exfoliated recently. In its bulk form, Black Phosphorus shows high carrier mobility (∼10 000 cm2/V·s) and a ∼0.3 eV direct band gap. Well-behaved p-type field-effect transistors with mobilities of up to 1000 cm2/V·s, as well as phototransistors, have been demonstrated on few-layer Black Phosphorus, showing its promise for electronics and optoelectronics applications due to its high hole mobility and thickness-dependent direct band gap. However, p–n junctions, the basic building blocks of modern electronic and optoelectronic devices, have not yet been realized based on Black Phosphorus. In this paper, we demonstrate a gate-tunable p–n diode based on a p-type Black Phosphorus/n-type monolayer MoS2 van der Waals p–n heterojunction. Upon illumination, these ultrathin p–n diodes show a maximum photodetection responsivity of 418 mA/W at the wavelength of 633 nm and photovoltaic energy conversion with an exter...
Yexin Deng - One of the best experts on this subject based on the ideXlab platform.
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anisotropic in plane thermal conductivity observed in few layer Black Phosphorus
Nature Communications, 2015Co-Authors: Zhe Luo, Yexin Deng, Jesse Maassen, Richard P Garrelts, Mark LundstromAbstract:Black Phosphorus has been revisited recently as a new two-dimensional material showing potential applications in electronics and optoelectronics. Here we report the anisotropic in-plane thermal conductivity of suspended few-layer Black Phosphorus measured by micro-Raman spectroscopy. The armchair and zigzag thermal conductivities are ∼20 and ∼40 W m(-1) K(-1) for Black Phosphorus films thicker than 15 nm, respectively, and decrease to ∼10 and ∼20 W m(-1) K(-1) as the film thickness is reduced, exhibiting significant anisotropy. The thermal conductivity anisotropic ratio is found to be ∼2 for thick Black Phosphorus films and drops to ∼1.5 for the thinnest 9.5-nm-thick film. Theoretical modelling reveals that the observed anisotropy is primarily related to the anisotropic phonon dispersion, whereas the intrinsic phonon scattering rates are found to be similar along the armchair and zigzag directions. Surface scattering in the Black Phosphorus films is shown to strongly suppress the contribution of long mean-free-path acoustic phonons.
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semiconducting Black Phosphorus synthesis transport properties and electronic applications
Chemical Society Reviews, 2015Co-Authors: Han Liu, Yexin Deng, Yuchen Du, Peide D YeAbstract:Phosphorus is one of the most abundant elements preserved in earth, and it comprises a fraction of ∼0.1% of the earth crust. In general, Phosphorus has several allotropes, and the two most commonly seen allotropes, i.e. white and red Phosphorus, are widely used in explosives and safety matches. In addition, Black Phosphorus, though rarely mentioned, is a layered semiconductor and has great potential in optical and electronic applications. Remarkably, this layered material can be reduced to one single atomic layer in the vertical direction owing to the van der Waals structure, and is known as phosphorene, in which the physical properties can be tremendously different from its bulk counterpart. In this review article, we trace back to the research history on Black Phosphorus of over 100 years from the synthesis to material properties, and extend the topic from Black Phosphorus to phosphorene. The physical and transport properties are highlighted for further applications in electronic and optoelectronics devices.
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Black Phosphorus monolayer mos2 van der waals heterojunction p n diode
ACS Nano, 2014Co-Authors: Yexin Deng, Nathan J. Conrad, Sina Najmaei, Xianfan Xu, Pulickel Madhavapanicker Ajayan, Yongji Gong, Peide D YeAbstract:Phosphorene, a elemental 2D material, which is the monolayer of Black Phosphorus, has been mechanically exfoliated recently. In its bulk form, Black Phosphorus shows high carrier mobility (∼10 000 cm2/V·s) and a ∼0.3 eV direct band gap. Well-behaved p-type field-effect transistors with mobilities of up to 1000 cm2/V·s, as well as phototransistors, have been demonstrated on few-layer Black Phosphorus, showing its promise for electronics and optoelectronics applications due to its high hole mobility and thickness-dependent direct band gap. However, p–n junctions, the basic building blocks of modern electronic and optoelectronic devices, have not yet been realized based on Black Phosphorus. In this paper, we demonstrate a gate-tunable p–n diode based on a p-type Black Phosphorus/n-type monolayer MoS2 van der Waals p–n heterojunction. Upon illumination, these ultrathin p–n diodes show a maximum photodetection responsivity of 418 mA/W at the wavelength of 633 nm and photovoltaic energy conversion with an exter...
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Black Phosphorus monolayer mos2 van der waals heterojunction p n diode
arXiv: Mesoscale and Nanoscale Physics, 2014Co-Authors: Yexin Deng, Nathan J. Conrad, Sina Najmaei, Pulickel Madhavapanicker Ajayan, Yongji Gong, Han Liu, Zhe Luo, Jun LouAbstract:Phosphorene, an elemental 2D material, which is the monolayer of Black Phosphorus, has been mechanically exfoliated recently. In its bulk form, Black Phosphorus shows high carrier mobility (~10000 cm2/Vs) and a ~0.3 eV direct bandgap. Well-behaved p-type field-effect transistors with mobilities of up to 1000 cm2/Vs, as well as phototransistors, have been demonstrated on few-layer Black Phosphorus, showing its promise for electronics and optoelectronics applications due to its high hole mobility and thickness-dependence direct bandgap. However, p-n junctions, the basic building blocks of modern electronic and optoelectronic devices, have not yet been realized based on Black Phosphorus. In this paper, we demonstrate a gate tunable p-n diode based on a p-type Black Phosphorus/n-type monolayer MoS2 van der Waals p-n heterojunction. Upon illumination, these ultra-thin p-n diodes show a maximum photodetection responsivity of 418 mA/W at the wavelength of 633 nm, and photovoltaic energy conversion with an external quantum efficiency of 0.3%. These p-n diodes show promise for broadband photodetection and solar energy harvesting.
Barbaros Ozyilmaz - One of the best experts on this subject based on the ideXlab platform.
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electron doping of ultrathin Black Phosphorus with cu adatoms
Nano Letters, 2016Co-Authors: Steven P Koenig, Kenji Watanabe, Takashi Taniguchi, Rostislav A Doganov, Leandro Seixas, A Carvalho, Jun You Tan, N L Yakovlev, Antonio Castro H Neto, Barbaros OzyilmazAbstract:Few-layer Black Phosphorus is a monatomic two-dimensional crystal with a direct band gap that has high carrier mobility for both holes and electrons. Similarly to other layered atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer Black Phosphorus is sensitive to surface impurities, adsorbates, and adatoms. Here we study the effect of Cu adatoms onto few-layer Black Phosphorus by characterizing few-layer Black Phosphorus field effect devices and by performing first-principles calculations. We find that the addition of Cu adatoms can be used to controllably n-dope few layer Black Phosphorus, thereby lowering the threshold voltage for n-type conduction without degrading the transport properties. We demonstrate a scalable 2D material-based complementary inverter which utilizes a boron nitride gate dielectric, a graphite gate, and a single bP crystal for both the p- and n-channels. The inverter operates at matched input and output voltages, exhibits a ...
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creating a stable oxide at the surface of Black Phosphorus
ACS Applied Materials & Interfaces, 2015Co-Authors: Mark T Edmonds, Steven P Koenig, Barbaros Ozyilmaz, A Carvalho, Antonio Castro H Neto, Anton Tadich, Angelo Ziletti, Kane M Odonnell, D F Coker, Michael S FuhrerAbstract:The stability of the surface of in situ cleaved Black Phosphorus crystals upon exposure to atmosphere is investigated with synchrotron-based photoelectron spectroscopy. After 2 days atmosphere exposure a stable subnanometer layer of primarily P2O5 forms at the surface. The work function increases by 0.1 eV from 3.9 eV for as-cleaved Black Phosphorus to 4.0 eV after formation of the 0.4 nm thick oxide, with Phosphorus core levels shifting by <0.1 eV. The results indicate minimal charge transfer, suggesting that the oxide layer is suitable for passivation or as an interface layer for further dielectric deposition.
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air stable transport in graphene contacted fully encapsulated ultrathin Black Phosphorus based field effect transistors
ACS Nano, 2015Co-Authors: Ahmet Avsar, Kenji Watanabe, Takashi Taniguchi, Antonio Castro H Neto, I J Veramarun, Barbaros OzyilmazAbstract:The presence of direct bandgap and high mobility in semiconductor few-layer Black Phosphorus offers an attractive prospect for using this material in future two-dimensional electronic devices. However, creation of barrier-free contacts which is necessary to achieve high performance in Black Phosphorus-based devices is challenging and currently limits their potential for applications. Here, we characterize fully encapsulated ultrathin (down to bilayer) Black Phosphorus field effect transistors fabricated under inert gas conditions by utilizing graphene as source–drain electrodes and boron nitride as an encapsulation layer. The observation of a linear ISD–VSD behavior with negligible temperature dependence shows that graphene electrodes lead to barrier-free contacts, solving the issue of Schottky barrier limited transport in the technologically relevant two-terminal field-effect transistor geometry. Such one-atom-thick conformal source–drain electrodes also enable the Black Phosphorus surface to be sealed, ...
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surface transfer doping induced effective modulation on ambipolar characteristics of few layer Black Phosphorus
Nature Communications, 2015Co-Authors: Du Xiang, A Castro H Neto, Jiadan Lin, Barbaros Ozyilmaz, Cheng Han, Shu Zhong, Yiyang Liu, Xueao Zhang, A T S Wee, Wei ChenAbstract:Black Phosphorus, a fast emerging two-dimensional material, has been configured as field effect transistors, showing a hole-transport-dominated ambipolar characteristic. Here we report an effective modulation on ambipolar characteristics of few-layer Black Phosphorus transistors through in situ surface functionalization with caesium carbonate (Cs2CO3) and molybdenum trioxide (MoO3), respectively. Cs2CO3 is found to strongly electron dope Black Phosphorus. The electron mobility of Black Phosphorus is significantly enhanced to similar to 27 cm(2)V(-1) s(-1) after 10 nm Cs2CO3 modification, indicating a greatly improved electron-transport behaviour. In contrast, MoO3 decoration demonstrates a giant hole-doping effect. In situ photoelectron spectroscopy characterization reveals significant surface charge transfer occurring at the dopants/Black Phosphorus interfaces. Moreover, the surface-doped Black Phosphorus devices exhibit a largely enhanced photodetection behaviour. Our findings coupled with the tunable nature of the surface transfer doping scheme ensure Black Phosphorus as a promising candidate for further complementary logic electronics.
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electric field effect in ultrathin Black Phosphorus
Applied Physics Letters, 2014Co-Authors: Steven P Koenig, A Castro H Neto, Rostislav A Doganov, Hennrik Schmidt, Barbaros OzyilmazAbstract:Black Phosphorus exhibits a layered structure similar to graphene, allowing mechanical exfoliation of ultrathin single crystals. Here, we demonstrate few-layer Black Phosphorus field effect devices on Si/SiO2 and measure charge carrier mobility in a four-probe configuration as well as drain current modulation in a two-point configuration. We find room-temperature mobilities of up to 300 cm2/Vs and drain current modulation of over 103. At low temperatures, the on-off ratio exceeds 105, and the device exhibits both electron and hole conduction. Using atomic force microscopy, we observe significant surface roughening of thin Black Phosphorus crystals over the course of 1 h after exfoliation.
Takashi Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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strain modulated bandgap and piezo resistive effect in Black Phosphorus field effect transistors
Nano Letters, 2017Co-Authors: Zuocheng Zhang, Guorui Chen, Kenji Watanabe, Takashi Taniguchi, X H Chen, Fangyuan Yang, Jason Horng, Nai Zhou Wang, Yu Zhang, Feng WangAbstract:Energy bandgap largely determines the optical and electronic properties of a semiconductor. Variable bandgap therefore makes versatile functionality possible in a single material. In layered material Black Phosphorus, the bandgap can be modulated by the number of layers; as a result, few-layer Black Phosphorus has discrete bandgap values that are relevant for optoelectronic applications in the spectral range from red, in monolayer, to mid-infrared in the bulk limit. Here, we further demonstrate continuous bandgap modulation by mechanical strain applied through flexible substrates. The strain-modulated bandgap significantly alters the density of thermally activated carriers; we for the first time observe a large piezo-resistive effect in Black Phosphorus field-effect transistors (FETs) at room temperature. The effect opens up opportunities for future development of electromechanical transducers based on Black Phosphorus, and we demonstrate an ultrasensitive strain gauge constructed from Black Phosphorus th...
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Strain-Modulated Bandgap and Piezo-Resistive Effect in Black Phosphorus Field-Effect Transistors
2017Co-Authors: Zuocheng Zhang, Guorui Chen, Kenji Watanabe, Fangyuan Yang, Jason Horng, Nai Zhou Wang, Yu Zhang, Takashi TaniguchiAbstract:Energy bandgap largely determines the optical and electronic properties of a semiconductor. Variable bandgap therefore makes versatile functionality possible in a single material. In layered material Black Phosphorus, the bandgap can be modulated by the number of layers; as a result, few-layer Black Phosphorus has discrete bandgap values that are relevant for optoelectronic applications in the spectral range from red, in monolayer, to mid-infrared in the bulk limit. Here, we further demonstrate continuous bandgap modulation by mechanical strain applied through flexible substrates. The strain-modulated bandgap significantly alters the density of thermally activated carriers; we for the first time observe a large piezo-resistive effect in Black Phosphorus field-effect transistors (FETs) at room temperature. The effect opens up opportunities for future development of electromechanical transducers based on Black Phosphorus, and we demonstrate an ultrasensitive strain gauge constructed from Black Phosphorus thin crystals
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quantum hall effect in Black Phosphorus two dimensional electron system
Nature Nanotechnology, 2016Co-Authors: Fangyuan Yang, Kenji Watanabe, Takashi Taniguchi, Zuocheng Zhang, Zengwei Zhu, Wenkai Lou, Xiaoying Zhou, Kai ChangAbstract:The development of new, high-quality functional materials has been at the forefront of condensed-matter research. The recent advent of two-dimensional Black Phosphorus has greatly enriched the materials base of two-dimensional electron systems (2DESs). Here, we report the observation of the integer quantum Hall effect in a high-quality Black Phosphorus 2DES. The high quality is achieved by embedding the Black Phosphorus 2DES in a van der Waals heterostructure close to a graphite back gate; the graphite gate screens the impurity potential in the 2DES and brings the carrier Hall mobility up to 6,000 cm(2) V(-1) s(-1). The exceptional mobility enabled us to observe the quantum Hall effect and to gain important information on the energetics of the spin-split Landau levels in Black Phosphorus. Our results set the stage for further study on quantum transport and device application in the ultrahigh mobility regime.
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electron doping of ultrathin Black Phosphorus with cu adatoms
Nano Letters, 2016Co-Authors: Steven P Koenig, Kenji Watanabe, Takashi Taniguchi, Rostislav A Doganov, Leandro Seixas, A Carvalho, Jun You Tan, N L Yakovlev, Antonio Castro H Neto, Barbaros OzyilmazAbstract:Few-layer Black Phosphorus is a monatomic two-dimensional crystal with a direct band gap that has high carrier mobility for both holes and electrons. Similarly to other layered atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer Black Phosphorus is sensitive to surface impurities, adsorbates, and adatoms. Here we study the effect of Cu adatoms onto few-layer Black Phosphorus by characterizing few-layer Black Phosphorus field effect devices and by performing first-principles calculations. We find that the addition of Cu adatoms can be used to controllably n-dope few layer Black Phosphorus, thereby lowering the threshold voltage for n-type conduction without degrading the transport properties. We demonstrate a scalable 2D material-based complementary inverter which utilizes a boron nitride gate dielectric, a graphite gate, and a single bP crystal for both the p- and n-channels. The inverter operates at matched input and output voltages, exhibits a ...
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quantum oscillations in a two dimensional electron gas in Black Phosphorus thin films
Nature Nanotechnology, 2015Co-Authors: Vy Tran, Ruixiang Fei, Guorui Chen, Huichao Wang, Jian Wang, Kenji Watanabe, Takashi Taniguchi, Li Yang, X H Chen, Yuanbo ZhangAbstract:The high material quality achieved in Black Phosphorus thin films combined with the choice of an appropriate substrate enables the electrostatic formation of a high-mobility two-dimensional electron gas that exhibits quantum oscillations in its magnetoresistance.