27 Jul 04:16
by Hao Wu,
Felix Groß,
Bingqian Dai,
David Lujan,
Seyed Armin Razavi,
Peng Zhang,
Yuxiang Liu,
Kemal Sobotkiewich,
Johannes Förster,
Markus Weigand,
Gisela Schütz,
Xiaoqin Li,
Joachim Gräfe,
Kang L. Wang
The strong spin–orbit coupling in topological surface states provides a large interfacial noncollinear Dzyaloshinskii–Moriya interaction in topological insulator/ferrimagnet heterostructures, resulting in small‐size (radius around 100 nm) skyrmions in the adjacent ferrimagnet at room temperature, where antiferromagnetically coupled skyrmion sublattices are observed.
Abstract
Magnetic skyrmions are topologically nontrivial chiral spin textures that have potential applications in next‐generation energy‐efficient and high‐density spintronic devices. In general, the chiral spins of skyrmions are stabilized by the noncollinear Dzyaloshinskii–Moriya interaction (DMI), originating from the inversion symmetry breaking combined with the strong spin–orbit coupling (SOC). Here, the strong SOC from topological insulators (TIs) is utilized to provide a large interfacial DMI in TI/ferrimagnet heterostructures at room temperature, resulting in small‐size (radius ≈ 100 nm) skyrmions in the adjacent ferrimagnet. Antiferromagnetically coupled skyrmion sublattices are observed in the ferrimagnet by element‐resolved scanning transmission X‐ray microscopy, showing the potential of a vanishing skyrmion Hall effect and ultrafast skyrmion dynamics. The line‐scan spin profile of the single skyrmion shows a Néel‐type domain wall structure and a 120 nm size of the 180° domain wall. This work demonstrates the sizable DMI and small skyrmions in TI‐based heterostructures with great promise for low‐energy spintronic devices.
20 Jul 02:34
by Sri Venkata Narayana Pammi,
Van‐Dang Tran,
Reddeppa Maddaka,
Ji‐Ho Eom,
Jang Su Jung,
Hyeon‐Myeon Jeong,
Moon‐Deock Kim,
Vincenzo Pecunia,
Soon Gil Yoon
This study presents an approach to halide perovskite photodetectors leading to cutting‐edge performance and stability. This approach combines bromine doping of MAPbI3 films and CVD as the perovskite deposition method. These findings inspire future efforts in the development of stable perovskite photodetectors under strong, prolonged illumination, thereby paving the way for their use in outdoor applications.
Abstract
Hybrid lead‐halide perovskite photodetectors represent a highly promising technology, but long‐term operational stability under ambient conditions must be improved before these devices can be deployed in real‐world applications. In consideration of the relationship between film quality and device stability, this work explored photodetectors based on bromine‐doped CH3NH3PbI3 (i.e., CH3NH3PbI3−
x
Br
x
, MAPbI3−
x
Br
x
in short form) perovskite layers deposited via chemical vapor deposition (CVD). These layers have good compactness and no pinholes, hence they enable sandwich‐type photodetectors with high performance in self‐powered mode. Under 632 nm illumination, these photodetectors achieve a level of responsivity as high as 45 A/W, along with a specific detectivity of 1.15 × 1014 Jones and an external quantum efficiency of 8.84 × 103%. It is important to note that these photodetectors exhibit outstanding operational stability that is superior to that of their pure‐iodide (i.e., CH3NH3PbI3, MAPbI3 in short form) counterparts. When the MAPbI3−
x
Br
x
devices are stressed under simulated solar illumination in ambient air, their photoresponse is maintained to within 29% loss of the original value for more than 500 h, while the photoresponse of the MAPbI3 devices is reduced by 62%. The key figures of merit of the fabricated devices and their operational level of photostability are expected to create new avenues for future outdoor photodetector applications.
20 Jul 02:33
by Ying Sun,
Taige Dong,
Linwei Yu,
Jun Xu,
Kunji Chen
Precise location, orientation, and layout controls of self‐assembled semiconducting nanowires, grown or transferred on planar substrates, are indispensable capabilities to accomplish scalable electronic device integration. The latest technologies developed for achieving orderly in‐plane guided growth, transferring, and integration of inorganic nanowires are reviewed, followed by a summary of their device applications in logic applications, photodetectors, stretchable electronics, and 3D stacked‐channel integration.
Abstract
Silicon and other inorganic semiconductor nanowires (NWs) have been extensively investigated in the last two decades for constructing high‐performance nanoelectronics, sensors, and optoelectronics. For many of these applications, these tiny building blocks have to be integrated into the existing planar electronic platform, where precise location, orientation, and layout controls are indispensable. In the advent of More‐than‐Moore's era, there are also emerging demands for a programmable growth engineering of the geometry, composition, and line‐shape of NWs on planar or out‐of‐plane 3D sidewall surfaces. Here, the critical technologies established for synthesis, transferring, and assembly of NWs upon planar surface are examined; then, the recent progress of in‐plane growth of horizontal NWs directly upon crystalline or patterned substrates, constrained by using nanochannels, an epitaxial interface, or amorphous thin film precursors is discussed. Finally, the unique capabilities of planar growth of NWs in achieving precise guided growth control, programmable geometry, composition, and line‐shape engineering are reviewed, followed by their latest device applications in building high‐performance field‐effect transistors, photodetectors, stretchable electronics, and 3D stacked‐channel integration.
20 Jul 02:30
by Shi‐Jun Liang,
Bin Cheng,
Xinyi Cui,
Feng Miao
The diverse properties of van der Waals heterostructures open unprecedented opportunities for various types of device applications inaccessible in conventional heterostructure materials. Research progress of vertical heterostructure device applications in vertical transistors, infrared photodetectors, and spintronic devices is reviewed, together with a discussion on the challenges and opportunities in the future development of multifunctional devices.
Abstract
The discovery of two‐dimensional (2D) materials with unique electronic, superior optoelectronic, or intrinsic magnetic order has triggered worldwide interest in the fields of material science, condensed matter physics, and device physics. Vertically stacking 2D materials with distinct electronic and optical as well as magnetic properties enables the creation of a large variety of van der Waals heterostructures. The diverse properties of the vertical heterostructures open unprecedented opportunities for various kinds of device applications, e.g., vertical field‐effect transistors, ultrasensitive infrared photodetectors, spin‐filtering devices, and so on, which are inaccessible in conventional material heterostructures. Here, the current status of vertical heterostructure device applications in vertical transistors, infrared photodetectors, and spintronic memory/transistors is reviewed. The relevant challenges for achieving high‐performance devices are presented. An outlook into the future development of vertical heterostructure devices with integrated electronic and optoelectronic as well as spintronic functionalities is also provided.
20 Jul 02:23
by Qiang Wu,
Lijun Yang,
Xizhang Wang,
Zheng Hu
Carbon‐based nanocages have emerged as a new platform for advanced energy storage and conversion owing to their hollow interior cavity with microchannels across the shells, their high specific surface area with defective outer surface, and their tunable electronic structure. Up‐to‐date progress on the synthesis, encapsulating/supporting of carbon‐based nanocages and their applications is presented, along with the research challenges and trends.
Abstract
Energy storage and conversion play a crucial role in modern energy systems, and the exploration of advanced electrode materials is vital but challenging. Carbon‐based nanocages consisting of sp2 carbon shells feature a hollow interior cavity with sub‐nanometer microchannels across the shells, high specific surface area with a defective outer surface, and tunable electronic structure, much different from the intensively studied nanocarbons such as carbon nanotubes and graphene. These structural and morphological characteristics make carbon‐based nanocages a new platform for advanced energy storage and conversion. Up‐to‐date synthetic strategies of carbon‐based nanocages, the utilization of their unique porous structure and morphology for the construction of composites with foreign active species, and their significant applications to the advanced energy storage and conversion are reviewed. Structure–performance correlations are discussed in depth to highlight the contribution of carbon‐based nanocages. The research challenges and trends are also envisaged for deepening and extending the study and application of this multifunctional material.
20 Jul 02:18
by Qiming Sun,
Ning Wang,
Qiang Xu,
Jihong Yu
Recent research progress on nanopore‐supported metal nanocatalysts for H2 generation from various liquid‐phase chemical hydrogen storage materials is reviewed, mainly focusing on the presentation of state‐of‐the‐art synthetic strategies and advanced characterizations of these nanocatalysts and their catalytic performances in hydrogen generation. Some drawbacks of each hydrogen storage system and challenges and opportunities in future research are also highlighted.
Abstract
Hydrogen has emerged as an environmentally attractive fuel and a promising energy carrier for future applications to meet the ever‐increasing energy challenges. The safe and efficient storage and release of hydrogen remain a bottleneck for realizing the upcoming hydrogen economy. Hydrogen storage based on liquid‐phase chemical hydrogen storage materials is one of the most promising hydrogen storage techniques, which offers considerable potential for large‐scale practical applications for its excellent safety, great convenience, and high efficiency. Recently, nanopore‐supported metal nanocatalysts have stood out remarkably in boosting the field of liquid‐phase chemical hydrogen storage. Herein, the latest research progress in catalytic hydrogen production is summarized, from liquid‐phase chemical hydrogen storage materials, such as formic acid, ammonia borane, hydrous hydrazine, and sodium borohydride, by using metal nanocatalysts confined within diverse nanoporous materials, such as metal–organic frameworks, porous carbons, zeolites, mesoporous silica, and porous organic polymers. The state‐of‐the‐art synthetic strategies and advanced characterizations for these nanocatalysts, as well as their catalytic performances in hydrogen generation, are presented. The limitation of each hydrogen storage system and future challenges and opportunities on this subject are also discussed. References in related fields are provided, and more developments and applications to achieve hydrogen energy will be inspired.
20 Jul 02:06
by Boyu Peng,
Ke Cao,
Albert Ho Yuen Lau,
Ming Chen,
Yang Lu,
Paddy K. L. Chan
Contact resistance and intrinsic gain are important performance indicators of organic field‐effect transistors. Staggered‐structure devices based on highly crystallized monolayer organic semiconductor provide outstanding contact, carrier mobility, and intrinsic gain. Organic 2D materials can potentially play an important role in next‐generation flexible electronics.
Abstract
The contact resistance limits the downscaling and operating range of organic field‐effect transistors (OFETs). Access resistance through multilayers of molecules and the nonideal metal/semiconductor interface are two major bottlenecks preventing the lowering of the contact resistance. In this work, monolayer (1L) organic crystals and nondestructive electrodes are utilized to overcome the abovementioned challenges. High intrinsic mobility of 12.5 cm2 V−1 s−1 and Ohmic contact resistance of 40 Ω cm are achieved. Unlike the thermionic emission in common Schottky contacts, the carriers are predominantly injected by field emission. The 1L‐OFETs can operate linearly from V
DS = −1 V to V
DS as small as −0.1 mV. Thanks to the good pinch‐off behavior brought by the monolayer semiconductor, the 1L‐OFETs show high intrinsic gain at the saturation regime. At a high bias load, a maximum current density of 4.2 µA µm−1 is achieved by the only molecular layer as the active channel, with a current saturation effect being observed. In addition to the low contact resistance and high‐resolution lithography, it is suggested that the thermal management of high‐mobility OFETs will be the next major challenge in achieving high‐speed densely integrated flexible electronics.
20 Jul 02:06
by Hui Chen,
Xiao Liang,
Yipu Liu,
Xuan Ai,
Tewodros Asefa,
Xiaoxin Zou
Porous electrocatalysts are the most popular class of materials that can provide a large density of accessible active sites and efficient mass transport. Representative progress of active site engineering in porous electrocatalysts for efficient electrocatalysis of hydrogen evolution reaction, oxygen reduction reaction, CO2 reduction reaction, nitrogen reduction reaction, and oxygen evolution reaction, are reviewed.
Abstract
Electrocatalysis is at the center of many sustainable energy conversion technologies that are being developed to reduce the dependence on fossil fuels. The past decade has witnessed significant progresses in the exploitation of advanced electrocatalysts for diverse electrochemical reactions involved in electrolyzers and fuel cells, such as the hydrogen evolution reaction (HER), the oxygen reduction reaction (ORR), the CO2 reduction reaction (CO2RR), the nitrogen reduction reaction (NRR), and the oxygen evolution reaction (OER). Herein, the recent research advances made in porous electrocatalysts for these five important reactions are reviewed. In the discussions, an attempt is made to highlight the advantages of porous electrocatalysts in multiobjective optimization of surface active sites including not only their density and accessibility but also their intrinsic activity. First, the current knowledge about electrocatalytic active sites is briefly summarized. Then, the electrocatalytic mechanisms of the five above‐mentioned reactions (HER, ORR, CO2RR, NRR, and OER), the current challenges faced by these reactions, and the recent efforts to meet these challenges using porous electrocatalysts are examined. Finally, the future research directions on porous electrocatalysts including synthetic strategies leading to these materials, insights into their active sites, and the standardized tests and the performance requirements involved are discussed.
20 Jul 02:03
by Hao Wu,
Felix Groß,
Bingqian Dai,
David Lujan,
Seyed Armin Razavi,
Peng Zhang,
Yuxiang Liu,
Kemal Sobotkiewich,
Johannes Förster,
Markus Weigand,
Gisela Schütz,
Xiaoqin Li,
Joachim Gräfe,
Kang L. Wang
The strong spin–orbit coupling in topological surface states provides a large interfacial noncollinear Dzyaloshinskii–Moriya interaction in topological insulator/ferrimagnet heterostructures, resulting in small‐size (radius around 100 nm) skyrmions in the adjacent ferrimagnet at room temperature, where antiferromagnetically coupled skyrmion sublattices are observed.
Abstract
Magnetic skyrmions are topologically nontrivial chiral spin textures that have potential applications in next‐generation energy‐efficient and high‐density spintronic devices. In general, the chiral spins of skyrmions are stabilized by the noncollinear Dzyaloshinskii–Moriya interaction (DMI), originating from the inversion symmetry breaking combined with the strong spin–orbit coupling (SOC). Here, the strong SOC from topological insulators (TIs) is utilized to provide a large interfacial DMI in TI/ferrimagnet heterostructures at room temperature, resulting in small‐size (radius ≈ 100 nm) skyrmions in the adjacent ferrimagnet. Antiferromagnetically coupled skyrmion sublattices are observed in the ferrimagnet by element‐resolved scanning transmission X‐ray microscopy, showing the potential of a vanishing skyrmion Hall effect and ultrafast skyrmion dynamics. The line‐scan spin profile of the single skyrmion shows a Néel‐type domain wall structure and a 120 nm size of the 180° domain wall. This work demonstrates the sizable DMI and small skyrmions in TI‐based heterostructures with great promise for low‐energy spintronic devices.
20 Jul 02:03
by Pranay Ranjan,
Jang Mee Lee,
Prashant Kumar,
Ajayan Vinu
Borophene is considered as one of the most promising 2D nanomaterials, owing to its unique structural and electronic properties. The various synthetic approaches for the fabrication of borophene nanostructures with different phases and morphologies, including free‐standing borophene sheets, are described. The frontline applications of these nanostructures in flexible electronics, sensing, disease diagnosis, catalysis, and hybrid energy storage are also considered.
Abstract
Borophene, a 2D allotrope of boron and the lightest elemental Dirac material, is the latest very promising 2D material owing to its unique structural and electronic characteristics of the X3 and β12 phases. The high atomic density on ridgelines of the β12 phase of borophene provides a substantial orbital overlap, which leads to an excellent electron density in the conduction level and thus to a highly metallic behavior. These unique structural characteristics and electronic properties of borophene attract significant scientific interest. Herein, approaches for crystal growth/synthesis of these unique nanostructures and their potential technological applications are discussed. Various substrate‐supported ultrahigh‐vacuum growth techniques for borophene, such as molecular beam epitaxy, atomic layer deposition, and chemical vapor deposition, along with their challenges, are also summarized. The sonochemical exfoliation and modified Hummer's technique for the synthesis of free‐standing borophene are also discussed. Solution‐phase exfoliation seems to address the scalability issues and expands the applications of these unique materials to various fields, including renewable energy devices and ultrafast sensors. Furthermore, the electronic, optical, thermal, and elastic properties of borophene are thoroughly discussed and are compared with those of graphene and its “cousins.” Numerous frontline applications are envisaged and an outlook is presented.
20 Jul 02:00
by Anna W. Kuziel,
Karolina Z. Milowska,
Pak‐Lee Chau,
Slawomir Boncel,
Krzysztof K. Koziol,
Noorhana Yahya,
Mike C. Payne
Pristine graphene flakes are 2D amphiphiles with well‐defined hydrophilic edges and hydrophobic basal plane surfaces, the interplay of which allows small flakes to be utilized as stabilizers. The interactions between flakes can be controlled by varying the flake size and the oil‐to‐water ratio. Pristine graphene flakes can stabilize water/oil emulsions even under high pressure, high temperature, and in saline solutions.
Abstract
The fundamental colloidal properties of pristine graphene flakes remain incompletely understood, with conflicting reports about their chemical character, hindering potential applications that could exploit the extraordinary electronic, thermal, and mechanical properties of graphene. Here, the true amphipathic nature of pristine graphene flakes is demonstrated through wet‐chemistry testing, optical microscopy, electron microscopy, and density functional theory, molecular dynamics, and Monte Carlo calculations, and it is shown how this fact paves the way for the formation of ultrastable water/oil emulsions. In contrast to commonly used graphene oxide flakes, pristine graphene flakes possess well‐defined hydrophobic and hydrophilic regions: the basal plane and edges, respectively, the interplay of which allows small flakes to be utilized as stabilizers with an amphipathic strength that depends on the edge‐to‐surface ratio. The interactions between flakes can be also controlled by varying the oil‐to‐water ratio. In addition, it is predicted that graphene flakes can be efficiently used as a new‐generation stabilizer that is active under high pressure, high temperature, and in saline solutions, greatly enhancing the efficiency and functionality of applications based on this material.
13 Jul 10:42
by Zhaoyang Liu,
Haixin Qiu,
Can Wang,
Zongping Chen,
Björn Zyska,
Akimitsu Narita,
Artur Ciesielski,
Stefan Hecht,
Lifeng Chi,
Klaus Müllen,
Paolo Samorì
Mixed‐dimensional van der Waals heterostructures (VDWHs) are fabricated based on 1D graphene nanoribbons onto 2D MoS2, showing a significantly suppressed persistent photoconductivity effect of MoS2. Photomodulation of the charge transport of the obtained VDWHs field‐effect transistor is realized by interfacing with photochromic molecules, demonstrating its great potential for multilevel memories, which are promising for future development of ultrathin multifunctional optoelectronics.
Abstract
Van der Waals heterostructures (VDWHs), obtained via the controlled assembly of 2D atomically thin crystals, exhibit unique physicochemical properties, rendering them prototypical building blocks to explore new physics and for applications in optoelectronics. As the emerging alternatives to graphene, monolayer transition metal dichalcogenides and bottom‐up synthesized graphene nanoribbons (GNRs) are promising candidates for overcoming the shortcomings of graphene, such as the absence of a bandgap in its electronic structure, which is essential in optoelectronics. Herein, VDWHs comprising GNRs onto monolayer MoS2 are fabricated. Field‐effect transistors (FETs) based on such VDWHs show an efficient suppression of the persistent photoconductivity typical of MoS2, resulting from the interfacial charge transfer process. The MoS2‐GNR FETs exhibit drastically reduced hysteresis and more stable behavior in the transfer characteristics, which is a prerequisite for the further photomodulation of charge transport behavior within the MoS2‐GNR VDWHs. The physisorption of photochromic molecules onto the MoS2‐GNR VDWHs enables reversible light‐driven control over charge transport. In particular, the drain current of the MoS2‐GNR FET can be photomodulated by 52%, without displaying significant fatigue over at least 10 cycles. Moreover, four distinguishable output current levels can be achieved, demonstrating the great potential of MoS2‐GNR VDWHs for multilevel memory devices.
13 Jul 10:38
by Sanghyeon Park,
Changmin Kim,
Sung O. Park,
Nam Khen Oh,
Ungsoo Kim,
Junghyun Lee,
Jihyung Seo,
Yejin Yang,
Hyeong Yong Lim,
Sang Kyu Kwak,
Guntae Kim,
Hyesung Park
High‐purity 1T‐MoS2 is successfully synthesized by the molten‐metal‐assisted intercalation (MMI) approach, which exploits the capillary action of molten potassium metal and the difference between the electron affinity of MoS2 and the ionization potential of potassium. The potassium dopants maintain a high electron density in the Mo d orbitals. Consequently, the 1T‐MoS2 (MMI) shows excellent phase stability and great promise as a non‐noble‐metal‐based electrocatalyst.
Abstract
The crystalline phase of layered transition metal dichalcogenides (TMDs) directly determines their material property. The most thermodynamically stable phase structures in TMDs are the semiconducting 2H and metastable metallic 1T phases. To overcome the low phase purity and instability of 1T‐TMDs, which limits the utilization of their intrinsic properties, various synthesis strategies for 1T‐TMDs have been proposed in phase‐engineering studies. Herein, a facile and scalable synthesis of 1T‐phase molybdenum disulfide (MoS2) via the molten‐metal‐assisted intercalation (MMI) approach is introduced, which exploits the capillary action of molten potassium and the difference between the electron affinity of MoS2 and the ionization potential of potassium. Highly reactive molten potassium metal can readily intercalate into the MoS2 interlayers, inducing an efficient phase transition from the 2H to 1T crystal structure. The ionic bonding between the intercalated potassium and sulfur lowers the energy barrier of the 1T‐phase transition, enhancing the phase stability of the 1T crystals. Owing to the high purity and stability of the 1T phase, the electrocatalytic performance for the hydrogen evolution reaction is significantly higher in 1T‐MoS2 (MMI) than in 2H‐MoS2 and even in 1T‐MoS2 synthesized using n‐butyllithium.
02 Jul 02:13
by Kyaw Zin Latt†, John A. Schlueter‡, Pierre Darancet§, and Saw-Wai Hla*†§
ACS Nano
DOI: 10.1021/acsnano.0c03694
02 Jul 02:12
by Jianping Shi*†‡#, Yahuan Huan†#, Mengmeng Xiao§, Min Hong†, Xiaoxu Zhao?, Yinlu Gao?, Fangfang Cui†, Pengfei Yang†, Stephen John Pennycook?, Jijun Zhao?, and Yanfeng Zhang*†
ACS Nano
DOI: 10.1021/acsnano.0c03940
02 Jul 02:12
by Yuanfei Ai†‡?, Shu-Chi Wu‡???, Kuangye Wang‡??, Tzu-Yi Yang‡??, Mingjin Liu‡??, Hsiang-Ju Liao‡??, Jiachen Sun†, Jyun-Hong Chen‡??, Shin-Yi Tang‡, Ding Chou Wu‡, Teng-Yu Su‡??, Yi-Chung Wang†‡, Hsuan-Chu Chen‡??, Shan Zhang‡??, Wen-Wu Liu§, Yu-Ze Chen#, Ling Lee†‡??, Jr-Hau He?, Zhiming M. Wang*†, and Yu-Lun Chueh*‡??
ACS Nano
DOI: 10.1021/acsnano.0c02831
02 Jul 02:11
by Kinga Lasek†, Paula Mariel Coelho†, Krzysztof Zberecki‡, Yan Xin§, Sadhu K. Kolekar†, Jingfeng Li†, and Matthias Batzill*†
ACS Nano
DOI: 10.1021/acsnano.0c02712
02 Jul 02:11
by Seoungwoong Park†‡?, Aram Lee†?, Kwang-Hun Choi†, Seok-Ki Hyeong†, Sukang Bae†, Jae-Min Hong†, Tae-Wook Kim§, Byung Hee Hong*‡, and Seoung-Ki Lee*†
ACS Nano
DOI: 10.1021/acsnano.0c02745
02 Jul 02:11
by Soniya S. Raja†, Chang-Wei Cheng‡, Yungang Sang‡§, Chun-An Chen#, Xin-Quan Zhang#, Abhishek Dubey#, Ta-Jen Yen#, Yu-Ming Chang&, Yi-Hsien Lee#, and Shangjr Gwo*†‡?
ACS Nano
DOI: 10.1021/acsnano.0c03462
02 Jul 02:10
by Li Wang†?, Ying Wu†?, Yayun Yu‡?, Aixi Chen†, Huifang Li†, Wei Ren†?, Shuai Lu†, Sunan Ding*†?, Hui Yang†, Qi-Kun Xue§, Fang-Sen Li*†?, and Guang Wang*‡§
ACS Nano
DOI: 10.1021/acsnano.0c02072
02 Jul 02:07
by Jiahua Duan†‡, Nathaniel Capote-Robayna§, Javier Taboada-Gutie´rrez†‡, Gonzalo A´lvarez-Pe´rez†‡, Iva´n Prieto?, Javier Marti´n-Sa´nchez†‡, Alexey Y. Nikitin*§?, and Pablo Alonso-Gonza´lez*†‡
Nano Letters
DOI: 10.1021/acs.nanolett.0c01673
02 Jul 02:07
by Xue Liu†, Jiajie Pei†‡, Zehua Hu†, Weijie Zhao†, Sheng Liu†, Mohamed-Raouf Amara†, Kenji Watanabe§, Takashi Taniguchi?, Han Zhang‡, and Qihua Xiong†?*
Nano Letters
DOI: 10.1021/acs.nanolett.0c01722
02 Jul 02:06
by Jiaojian Shi?†, Edoardo Baldini?‡, Simone Latini¶, Shunsuke A. Sato§¶, Yaqing Zhang†, Brandt C. Pein†, Pin-Chun Shen?, Jing Kong?, Angel Rubio¶?#, Nuh Gedik‡, and Keith A. Nelson*†
Nano Letters
DOI: 10.1021/acs.nanolett.0c01134
02 Jul 02:05
by Yue Luo*†‡§?, Na Liu†‡, Bumho Kim?, James Hone?, and Stefan Strauf*†‡
Nano Letters
DOI: 10.1021/acs.nanolett.0c01358
02 Jul 02:05
by Zebo Zheng‡, Fengsheng Sun‡, Wuchao Huang, Jingyao Jiang, Runze Zhan, Yanlin Ke, Huanjun Chen*, and Shaozhi Deng*
Nano Letters
DOI: 10.1021/acs.nanolett.0c01627
02 Jul 02:04
by Rasmus H. Godiksen†‡, Shaojun Wang†‡§, T. V. Raziman†‡, Marcos H. D. Guimaraes†?, Jaime Go´mez Rivas†‡§, and Alberto G. Curto*†‡
Nano Letters
DOI: 10.1021/acs.nanolett.0c00756
02 Jul 02:04
by Jiawei Sun†, Huatian Hu†, Deng Pan§, Shunping Zhang*‡, and Hongxing Xu*†‡
Nano Letters
DOI: 10.1021/acs.nanolett.0c01019
02 Jul 02:03
by Gwang Hyuk Shin†, Cheolmin Park†, Khang June Lee, Hyeok Jun Jin, and Sung-Yool Choi*
Nano Letters
DOI: 10.1021/acs.nanolett.0c01460
02 Jul 01:58
by Ider Ronneberger,
Zeila Zanolli,
Matthias Wuttig,
Riccardo Mazzarello
A first‐principles study of the structure, bonding, and ferroelectricity in quasi 2D monochalcogenides (GeSe, GeTe, SnSe, SnTe) is carried out. It is found that a few bilayers are sufficient to recover bulk behavior in selenides, while tellurides deviate strongly from the bulk, even for thick models. These differences stem from the effects of depolarizing fields and the different bonding mechanisms.
Abstract
Extreme miniaturization is known to be detrimental for certain properties, such as ferroelectricity in perovskite oxide films below a critical thickness. Remarkably, few‐layer crystalline films of monochalcogenides display robust in‐plane ferroelectricity with potential applications in nanoelectronics. These applications critically depend on the electronic properties and the nature of bonding in the 2D limit. A fundamental open question is thus to what extent bulk properties persist in thin films. Here, this question is addressed by a first‐principles study of the structural, electronic, and ferroelectric properties of selected monochalcogenides (GeSe, GeTe, SnSe, and SnTe) as a function of film thickness up to 18 bilayers. While in selenides a few bilayers are sufficient to recover the bulk behavior, the Te‐based compounds deviate strongly from the bulk, irrespective of the slab thickness. These results are explained in terms of depolarizing fields in Te‐based slabs and the different nature of the chemical bond in selenides and tellurides. It is shown that GeTe and SnTe slabs inherit metavalent bonding of the bulk phase, despite structural and electronic properties being strongly modified in thin films. This understanding of the nature of bonding in few‐layers structures offers a powerful tool to tune materials properties for applications in information technology.
02 Jul 01:49
by Junyong Wang,
Yong Justin Zhou,
Du Xiang,
Shiuan Jun Ng,
Kenji Watanabe,
Takashi Taniguchi,
Goki Eda
Linearly polarized light‐emitting diodes are demonstrated using few‐layer ReS2, a 2D semiconductor with reduced in‐plane symmetry. Two excitonic electroluminescence peaks exhibiting high degrees of linear polarization of ≈80% are observed in near‐infrared frequencies. Hot hole injection through a hBN tunneling layer is shown to be key to the activation of hot exciton emission.
Abstract
An on‐chip polarized light source is desirable in signal processing, optical communication, and display applications. Layered semiconductors with reduced in‐plane symmetry have inherent anisotropic excitons that are attractive candidates as polarized dipole emitters. Herein, the demonstration of polarized light‐emitting diode based on anisotropic excitons in few‐layer ReS2, a 2D semiconductor with excitonic transition energy of 1.5–1.6 eV, is reported. The light‐emitting device is based on minority carrier (hole) injection into n‐type ReS2 through a hexagonal boron nitride (hBN) tunnel barrier in a metal–insulator–semiconductor (MIS) van der Waals heterostack. Two distinct emission peaks from excitons are observed at near‐infrared wavelength regime from few‐layer ReS2. The emissions exhibit a degree of polarization of 80% reflecting the nearly 1D nature of excitons in ReS2.