Multifunctional van der Waals Broken-Gap Heterojunction
TL;DR: The tunability of the BP work function with variation in flake thickness is exploited in order to demonstrate that a BP-based broken-gap heterojunction can manifest diverse current-transport characteristics such as gate tunable rectifying p-n junction diodes, Esaki diode, backward-rectifying diode, and nonrectifying devices as a consequence of diverse band-bending at the heteroj junction.
Abstract: The finite energy band-offset that appears between band structures of employed materials in a broken-gap heterojunction exhibits several interesting phenomena. Here, by employing a black phosphorus (BP)/rhenium disulfide (ReS2 ) heterojunction, the tunability of the BP work function (Φ BP ) with variation in flake thickness is exploited in order to demonstrate that a BP-based broken-gap heterojunction can manifest diverse current-transport characteristics such as gate tunable rectifying p-n junction diodes, Esaki diodes, backward-rectifying diodes, and nonrectifying devices as a consequence of diverse band-bending at the heterojunction. Diversity in band-bending near heterojunction is attributed to change in the Fermi level difference (Δ) between BP and ReS2 sides as a consequence of Φ BP modulation. No change in the current transport characteristics in several devices with fixed Δ also provides further evidence that current-transport is substantially impacted by band-bending at the heterojunction. Optoelectronic experiments on the Esaki diode and the p-n junction diode provide experimental evidence of band-bending diversity. Additionally, the p+ -n-p junction comprising BP (38 nm)/ReS2 /BP(5.8 nm) demonstrates multifunctionality of binary and ternary inverters as well as exhibiting the behavior of a bipolar junction transistor with common-emitter current gain up to 50.
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TL;DR: This article, which focuses on BP and BP-analogue materials, will present their crystal structure, properties, synthesis methods and applications and the future opportunities and challenges of the materials are included.
Abstract: Black phosphorus (BP), a novel two-dimensional (2D) layered semiconductor material, has attracted tremendous attention since 2014 due to its prominent carrier mobility, thickness-dependent direct bandgap and in-plane anisotropic physical properties. BP has been considered as a promising material for many applications, such as in transistors, photonics, optoelectronics, sensors, batteries and catalysis. However, the development of BP was hampered by its instability under ambient conditions, as well as by the lack of methods to synthesize large-area and high quality 2D nanofilms. Recently, some BP-analogue materials such as binary phosphides (MPx), transition metal phosphorus trichalcogenides (MPX3), and 2D group V (pnictogens) and 2D group VI materials have attracted increasing interest for their unique and stable structures, and excellent physical and chemical properties. This article, which focuses on BP and BP-analogue materials, will present their crystal structure, properties, synthesis methods and applications. Also the similarity and difference between BP and BP-analogue materials will be discussed, and the presentation of the future opportunities and challenges of the materials are included at the end.
220 citations
Journal Article•
TL;DR: In this paper, a few-layer black phosphorus crystals with thickness down to a few nanometres are used to construct field effect transistors for nanoelectronic devices. But the performance of these materials is limited.
Abstract: Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.
138 citations
TL;DR: 2D van der Waals heterostructures based on direct bandgap materials black phosphorus and rhenium disulfide for the nonvolatile ternary logic operations is demonstrated for the first time with the ultrathin oxide layer from the black phosphorus serving as the charge trapping as well as band‐to‐band tunneling layer.
Abstract: Nonvolatile logic devices have attracted intensive research attentions recently for energy efficiency computing, where data computing and storage can be realized in the same device structure. Various approaches have been adopted to build such devices; however, the functionality and versatility are still very limited. Here, 2D van der Waals heterostructures based on direct bandgap materials black phosphorus and rhenium disulfide for the nonvolatile ternary logic operations is demonstrated for the first time with the ultrathin oxide layer from the black phosphorus serving as the charge trapping as well as band-to-band tunneling layer. Furthermore, an artificial electronic synapse based on this heterostructure is demonstrated to mimic trilingual synaptic response by changing the input base voltage. Besides, artificial neural network simulation based on the electronic synaptic arrays using the handwritten digits data sets demonstrates a high recognition accuracy of 91.3%. This work provides a path toward realizing multifunctional nonvolatile logicin-memory applications based on novel 2D heterostructures.
70 citations
TL;DR: In this article, a Van der Waals tunneling heterostructure is proposed for near-infrared photodetection by combining WSe2 and Bi2Se3, which shows an ultralow dark current below pico-ampere and a high tunnelingdominated photocurrent.
Abstract: Tunneling heterostructures are emerging as a versatile architecture for photodetection due to their advanced optical sensitivity, tailorable detection band, and well- balanced photoelectric performances However, the existing tunneling heterostructures are mainly operated in the visible wavelengths and have been rarely investigated for the near-infrared detection Herein, we report the design and realization of a novel broken-gap tunneling heterostructure by combining WSe2 and Bi2Se3, which is able to realize the simultaneous visible and near-infrared detection because of the complementary bandgaps of WSe2 and Bi2Se3 (146 and 03 eV, respectively) Thanks to the realigned band structure, the heterostructure shows an ultralow dark current below pico-ampere and a high tunneling-dominated photocurrent The photodetector based on our tunneling heterostructure exhibits a superior specific detectivity of 79× 1012 Jones for a visible incident of 532 nm and 22× 1010 Jones for a 1456 nm near-infrared illumination Our study demonstrates a new band structure engineering avenue for the construction of van der Waals tunneling heterostructures for high-performance wide band photodetection
70 citations
TL;DR: In this article, a broken-gap van der Waals (vdW) heterojunction with a bilateral accumulation region design and a big band offset was proposed, which exhibits an ultrahigh reverser rectification ratio approaching 108 and on/off ratio over 108 at room temperature.
Abstract: Broken-gap van der Waals (vdW) heterojunctions based on 2D materials are promising structures to fabricate high-speed switching and low-power multifunctional devices thanks to its charge transport versus quantum tunneling mechanism. However, the tunneling current is usually generated under both positive and negative bias voltage, resulting in small rectification and photocurrent on/off ratio. In this paper, we report a broken-gap vdW heterojunction PtS2/WSe2 with a bilateral accumulation region design and a big band offset by utilizing thick PtS2 as an effective carrier-selective contact, which exhibits an ultrahigh reverser rectification ratio approaching 108 and on/off ratio over 108 at room temperature. We also find excellent photodetection properties in such a heterodiode with a large photocurrent on/off ratio over 105 due to its ultralow forward current and a comparable photodetectivity of 3.8 × 1010 Jones. In addition, the response time of such a photodetector reaches 8 μs owing to the photoinduced tunneling mechanism and reduced interface trapping effect. The proposed heterojunction not only demonstrates the high-performance broken-gap heterodiode but also provides in-depth understanding of the tunneling mechanism in the development of future electronic and optoelectronic applications.
70 citations
References
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TL;DR: With steady improvement in fabrication techniques and using graphene’s springboard, van der Waals heterostructures should develop into a large field of their own.
Abstract: Fabrication techniques developed for graphene research allow the disassembly of many layered crystals (so-called van der Waals materials) into individual atomic planes and their reassembly into designer heterostructures, which reveal new properties and phenomena. Andre Geim and Irina Grigorieva offer a forward-looking review of the potential of layering two-dimensional materials into novel heterostructures held together by weak van der Waals interactions. Dozens of these one-atom- or one-molecule-thick crystals are known. Graphene has already been well studied but others, such as monolayers of hexagonal boron nitride, MoS2, WSe2, graphane, fluorographene, mica and silicene are attracting increasing interest. There are many other monolayers yet to be examined of course, and the possibility of combining graphene with other crystals adds even further options, offering exciting new opportunities for scientific exploration and technological innovation. Research on graphene and other two-dimensional atomic crystals is intense and is likely to remain one of the leading topics in condensed matter physics and materials science for many years. Looking beyond this field, isolated atomic planes can also be reassembled into designer heterostructures made layer by layer in a precisely chosen sequence. The first, already remarkably complex, such heterostructures (often referred to as ‘van der Waals’) have recently been fabricated and investigated, revealing unusual properties and new phenomena. Here we review this emerging research area and identify possible future directions. With steady improvement in fabrication techniques and using graphene’s springboard, van der Waals heterostructures should develop into a large field of their own.
8,162 citations
TL;DR: In this article, a few-layer black phosphorus crystals with thickness down to a few nanometres are used to construct field effect transistors for nanoelectronic devices. But the performance of these materials is limited.
Abstract: Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.
6,924 citations
TL;DR: In this article, the authors focus on the origin of the D and G peaks and the second order of D peak and show that the G and 2 D Raman peaks change in shape, position and relative intensity with number of graphene layers.
6,496 citations
TL;DR: A detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) is presented to predict its electrical and optical properties, finding that the mobilities are hole-dominated, rather high and highly anisotropic.
Abstract: Two-dimensional crystals are emerging materials for nanoelectronics. Development of the field requires candidate systems with both a high carrier mobility and, in contrast to graphene, a sufficiently large electronic bandgap. Here we present a detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) to predict its electrical and optical properties. This system has a direct bandgap, tunable from 1.51 eV for a monolayer to 0.59 eV for a five-layer sample. We predict that the mobilities are hole-dominated, rather high and highly anisotropic. The monolayer is exceptional in having an extremely high hole mobility (of order 10,000 cm(2) V(-1) s(-1)) and anomalous elastic properties which reverse the anisotropy. Light absorption spectra indicate linear dichroism between perpendicular in-plane directions, which allows optical determination of the crystalline orientation and optical activation of the anisotropic transport properties. These results make few-layer BP a promising candidate for future electronics.
3,622 citations
Pennsylvania State University1, Rensselaer Polytechnic Institute2, Oak Ridge National Laboratory3, University of Central Florida4, Yale University5, Purdue University6, Carnegie Mellon University7, Massachusetts Institute of Technology8, Lawrence Berkeley National Laboratory9, University of California, Berkeley10, Rice University11, Chinese Academy of Sciences12, University of Texas at Austin13, University of California, Santa Barbara14
TL;DR: Insight is provided into the theoretical modeling and understanding of the van der Waals forces that hold together the 2D layers in bulk solids, as well as their excitonic properties and growth morphologies.
Abstract: The isolation of graphene in 2004 from graphite was a defining moment for the “birth” of a field: two-dimensional (2D) materials In recent years, there has been a rapidly increasing number of papers focusing on non-graphene layered materials, including transition-metal dichalcogenides (TMDs), because of the new properties and applications that emerge upon 2D confinement Here, we review significant recent advances and important new developments in 2D materials “beyond graphene” We provide insight into the theoretical modeling and understanding of the van der Waals (vdW) forces that hold together the 2D layers in bulk solids, as well as their excitonic properties and growth morphologies Additionally, we highlight recent breakthroughs in TMD synthesis and characterization and discuss the newest families of 2D materials, including monoelement 2D materials (ie, silicene, phosphorene, etc) and transition metal carbide- and carbon nitride-based MXenes We then discuss the doping and functionalization of 2
2,036 citations