Nano Letters
DOI: 10.1021/acs.nanolett.9b02982
Xingxing Zhang
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09 Jan 01:36
[ASAP] Electronic Polarizability as the Fundamental Variable in the Dielectric Properties of Two-Dimensional Materials
by Tian Tian†#, Declan Scullion‡#, Dale Hughes‡, Lu Hua Li§, Chih-Jen Shih†, Jonathan Coleman?, Manish Chhowalla?, and Elton J. G. Santos*‡
jingjiniao, Xingxing Zhang and one other like this
09 Jan 01:35
Controlling Defects in Continuous 2D GaS Films for High‐Performance Wavelength‐Tunable UV‐Discriminating Photodetectors
by Yang Lu,
Jun Chen,
Tongxin Chen,
Yu Shu,
Ren‐Jie Chang,
Yuewen Sheng,
Viktoryia Shautsova,
Nhlakanipho Mkhize,
Philip Holdway,
Harish Bhaskaran,
Jamie H. Warner
A chemical vapor deposition method is developed for controlling defects in gallium(II) sulfide (GaS), and their influence on the UV photosensing response in devices is elucidated. Defects in GaS act as sites of photoinduced oxidation and degradation. High‐quality GaS 2D films show uniform UV photodetector response and defect tuning enables selective UV sensing.
Abstract
A chemical vapor deposition method is developed for thickness‐controlled (one to four layers), uniform, and continuous films of both defective gallium(II) sulfide (GaS): GaS0.87 and stoichiometric GaS. The unique degradation mechanism of GaS0.87 with X‐ray photoelectron spectroscopy and annular dark‐field scanning transmission electron microscopy is studied, and it is found that the poor stability and weak optical signal from GaS are strongly related to photo‐induced oxidation at defects. An enhanced stability of the stoichiometric GaS is demonstrated under laser and strong UV light, and by controlling defects in GaS, the photoresponse range can be changed from vis‐to‐UV to UV‐discriminating. The stoichiometric GaS is suitable for large‐scale, UV‐sensitive, high‐performance photodetector arrays for information encoding under large vis‐light noise, with short response time (<66 ms), excellent UV photoresponsivity (4.7 A W–1 for trilayer GaS), and 26‐times increase of signal‐to‐noise ratio compared with small‐bandgap 2D semiconductors. By comprehensive characterizations from atomic‐scale structures to large‐scale device performances in 2D semiconductors, the study provides insights into the role of defects, the importance of neglected material‐quality control, and how to enhance device performance, and both layer‐controlled defective GaS0.87 and stoichiometric GaS prove to be promising platforms for study of novel phenomena and new applications.
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30 Dec 11:44
Gap‐Mode Plasmon‐Induced Photovoltaic Effect in a Vertical Multilayer Graphene Homojunction
by Khang June Lee,
Kyungmok Kwon,
Shinho Kim,
Woonggi Hong,
Junghoon Park,
Kyoungsik Yu,
Sung‐Yool Choi
The gap‐mode plasmon‐induced photovoltaic effect is studied in a vertical homojunction of multilayer graphene. Multilayer graphene acts both as a photo‐carrier generation layer and as a spacer for gap‐mode plasmon. Such structural advantages can serve as a platform for building more efficient two‐dimensional (2D) materials‐based photodevices that overcome the trade‐off between photoresponsivity and photoresponse time.
Abstract
Gap‐mode plasmons that occur between metallic nanoparticles and metallic films separated by a thin spacer have been widely studied in the field of nano‐optics and plasmonics for enhancing the light–matter interaction of graphene and other two‐dimensional (2D) materials. However, efficient photovoltaic devices using such gap‐mode plasmons have not been achieved because of structural difficulties. Here, a gap‐mode plasmon‐induced asymmetric vertical homojunction photovoltaic device using multilayer graphene is presented. In this structure, the multilayer graphene acts both as a photo‐carrier generation layer and as a spacer for the gap‐mode plasmon. The optical absorption of graphene is further enhanced by the presence of gap‐mode plasmons, and the photoresponse time is extremely short because of the atomically short channel lengths across the vertical direction. The wavelength dependence of the gap‐mode plasmon is also investigated for three devices with different metal electrodes by photocurrent measurement at five different wavelengths and numerical simulations. The device strategies implemented in this work can enhance the performance of graphene‐based vertical photonic devices and can be applied to other 2D materials‐based photonic devices.
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30 Dec 11:43
2D Ductile Transition Metal Chalcogenides (TMCs): Novel High‐Performance Ag2S Nanosheets for Ultrafast Photonics
by Jiangjiang Feng,
Xiaohui Li,
Zhaojiang Shi,
Chuang Zheng,
Xuwei Li,
Deying Leng,
Yamin Wang,
Jie Liu,
Lujun Zhu
As a member of 2D transition metal chalcogenides (TMCs), 2D Ag2S with large absorption coefficient, broadband optical response, and unique layered structure has offered a platform for achieving disruptive successes in divisional fields. Ag2S saturable absorber (SA) is incorporated into an Er‐doped fiber laser to achieve 229th harmonic soliton molecule, corresponding to the repetition frequency of 1.1 GHz for the first time.
Abstract
As a member of 2D transition metal chalcogenides (TMCs), 2D Ag2S with large absorption coefficient, broadband optical response, extraordinary metal‐like ductility, high plastic deformation strain, unique layered structure, and very low solubility has offered a platform for achieving disruptive successes in divisional fields. Great achievements have been achieved in exploring the linear optical, mechanical, and photoelectric properties of 2D Ag2S nanosheets. However, the nonlinear optical properties of 2D Ag2S nanosheets and their applications in ultrafast photonics have not been studied. The saturable absorption property of 2D Ag2S nanosheets is experimentally illustrated at the telecommunication band with a large optical modulation depth of 15.5% and a low saturable intensity of 250.4 MW cm−2. Moreover, 229th harmonic soliton molecule with repetition rate of 1.1 GHz based on 2D Ag2S saturable absorber (SA) is realized at the telecommunication band for the first time to the authors' knowledge. Thankfully, 2D Ag2S nanosheets display excellent nonlinear optical properties suggesting that this may open a new door for advanced photonic devices based on 2D Ag2S nanosheets.
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30 Dec 11:42
[ASAP] Transition from Semimetal to Semiconductor in ZrTe2 Induced by Se Substitution
by Zahir Muhammad†?, Bo Zhang†?, Haifeng Lv‡, Huan Shan§, Zia ur Rehman†, Shuangming Chen†, Zhe Sun*†?, Xiaojun Wu‡, Aidi Zhao§, and Li Song*†
ACS Nano
DOI: 10.1021/acsnano.9b07931
yuanql@sjtu.edu.cn, Xingxing Zhang likes this
30 Dec 11:40
[ASAP] Observation and Active Control of a Collective Polariton Mode and Polaritonic Band Gap in Few-Layer WS2 Strongly Coupled with Plasmonic Lattices
by Wenjing Liu†, Yuhui Wang†, Biyuan Zheng‡, Minsoo Hwang†, Zhurun Ji†, Gerui Liu†, Ziwei Li‡, Volker J. Sorger§, Anlian Pan*‡, and Ritesh Agarwal*†
Nano Letters
DOI: 10.1021/acs.nanolett.9b05056
Xingxing Zhang, Alex Strasser likes this
30 Dec 11:40
[ASAP] Enhanced Piezoelectric Effect Derived from Grain Boundary in MoS2 Monolayers
by Mingjin Dai†‡?, Wei Zheng†‡??, Xi Zhang*§, Sanmei Wang§, Junhao Lin?, Kai Li?, Yunxia Hu†‡, Enwei Sun?, Jia Zhang‡, Yunfeng Qiu‡, Yongqing Fu#, Wenwu Cao?, and PingAn Hu*†‡?
Nano Letters
DOI: 10.1021/acs.nanolett.9b03642
Juanjuan, Xingxing Zhang likes this
30 Dec 11:39
[ASAP] Giant Valley-Zeeman Splitting from Spin-Singlet and Spin-Triplet Interlayer Excitons in WSe2/MoSe2 Heterostructure
by Tianmeng Wang†?, Shengnan Miao†?, Zhipeng Li†?, Yuze Meng†?, Zhengguang Lu‡§, Zhen Lian†, Mark Blei?, Takashi Taniguchi?, Kenji Watanabe?, Sefaattin Tongay*?, Dmitry Smirnov‡, and Su-Fei Shi*†#
Nano Letters
DOI: 10.1021/acs.nanolett.9b04528
Xingxing Zhang, jingjiniao and one other like this
30 Dec 11:39
[ASAP] Quantitative Nanoscale Absorption Mapping: A Novel Technique To Probe Optical Absorption of Two-Dimensional Materials
by Marco Negri†, Luca Francaviglia†, Dumitru Dumcenco†‡?, Matteo Bosi§, Daniel Kaplan?, Venkataraman Swaminathan??, Giancarlo Salviati§, Andras Kis‡, Filippo Fabbri*?, and Anna Fontcuberta i Morral*†#
Nano Letters
DOI: 10.1021/acs.nanolett.9b04304
Xingxing Zhang, Alex Strasser and 2 others like this
30 Dec 11:38
Atomic‐Scale Metal–Insulator Transition in SrRuO3 Ultrathin Films Triggered by Surface Termination Conversion
by Han Gyeol Lee,
Lingfei Wang,
Liang Si,
Xiaoyue He,
Daniel G. Porter,
Jeong Rae Kim,
Eun Kyo Ko,
Jinkwon Kim,
Sung Min Park,
Bongju Kim,
Andrew Thye Shen Wee,
Alessandro Bombardi,
Zhicheng Zhong,
Tae Won Noh
An atomic‐scale metal–insulator transition triggered by surface termination conversion in SrRuO3 ultrathin films is demonstrated. A water‐leaching method enables uniform and effective termination engineering at the SrRuO3(001) surface. As the surface termination converts from SrO to RuO2, a highly insulating and nonferromagnetic phase emerges within the topmost SrRuO3 monolayer due to the broken octahedral symmetry resulting in insulating orbital occupancy.
Abstract
The metal–insulator transition (MIT) in transition‐metal‐oxide is fertile ground for exploring intriguing physics and potential device applications. Here, an atomic‐scale MIT triggered by surface termination conversion in SrRuO3 ultrathin films is reported. Uniform and effective termination engineering at the SrRuO3(001) surface can be realized via a self‐limiting water‐leaching process. As the surface termination converts from SrO to RuO2, a highly insulating and nonferromagnetic phase emerges within the topmost SrRuO3 monolayer. Such a spatially confined MIT is corroborated by systematic characterizations on electrical transport, magnetism, and scanning tunneling spectroscopy. Density functional theory calculations and X‐ray linear dichroism further suggest that the surface termination conversion breaks the local octahedral symmetry of the crystal field. The resultant modulation in 4d orbital occupancy stabilizes a nonferromagnetic insulating surface state. This work introduces a new paradigm to stimulate and tune exotic functionalities of oxide heterostructures with atomic precision.
23 Dec 03:12
Controllable Synthesis of Crystalline ReS2(1−x)Se2x Monolayers on Amorphous SiO2/Si Substrates with Fast Photoresponse
by Peipei Kang,
Haiyan Nan,
Xiumei Zhang,
Haoxin Mo,
Zhenhua Ni,
Xiaofeng Gu,
Kostya (Ken) Ostrikov,
Shaoqing Xiao
High‐quality and large‐size ReS2(1− x )Se2 x monolayer films are prepared on amorphous SiO2/Si substrates by a controllable and reliable method that synergizes the effects of common salt (NaCl) and confined‐space synthesis in a versatile and scalable chemical vapor deposition process. The ReS2(1− x )Se2 x based photodetectors exhibit good photoresponse to visible and near‐infrared light with a fast response of less than 15 ms.
Abstract
Re‐based transition metal dichalcogenides (TMDs) and alloys have many unusual features such as in‐plane anisotropic optical, electrical, and phonon properties and thus receive increasing research interest. However, the distorted 1T structure and the weaker interlayer coupling easily cause anisotropic growth and out‐of‐plane growth, making it particularly challenging to produce Re‐based TMD and alloy monolayers on amorphous SiO2/Si substrates. Here, a reliable method is developed for the synthesis of high‐quality and large‐size ReS2(1− x )Se2 x monolayer crystals on SiO2/Si substrates by NaCl‐assisted, confined‐space chemical vapor deposition. The synergy of salt assistance with the confined reaction space facilitates the formation of intermediate metal oxychlorides and creates a relatively stable growth environment, finally leading to the successful synthesis of ReS2(1− x )Se2 x monolayer crystals on SiO2/Si substrates. The as‐grown ReS2(1− x )Se2 x monolayer alloys exhibit continuously variable composition, high crystal quality, and uniform distribution of Re, S, and Se elements. Furthermore, the ReS2(1− x )Se2 x based photodetectors display good photoresponse to visible and near‐infrared light with a fast response of less than 15 ms. The salt‐assisted, confined‐space chemical vapor deposition provides a reliable way for the synthesis of large‐scale low‐lattice symmetry 2D materials on amorphous SiO2/Si substrates and opens up new prospects for Re‐based TMDs and alloys in optoelectronic devices.
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23 Dec 03:10
[ASAP] Direct Laser Patterning and Phase Transformation of 2D PdSe2 Films for On-Demand Device Fabrication
by Viktoryia Shautsova*, Sapna Sinha, Linlin Hou, Qianyang Zhang, Martin Tweedie, Yang Lu, Yuewen Sheng, Benjamin F. Porter, Harish Bhaskaran, and Jamie H. Warner*
ACS Nano
DOI: 10.1021/acsnano.9b06892
Xingxing Zhang, Alex Strasser likes this
23 Dec 03:10
[ASAP] Reduced Binding Energy and Layer-Dependent Exciton Dynamics in Monolayer and Multilayer WS2
by Yuanshuang Liu, Xiangmin Hu, Ting Wang, and Dameng Liu*
ACS Nano
DOI: 10.1021/acsnano.9b08004
yuanql@sjtu.edu.cn, Xingxing Zhang and 2 others like this
23 Dec 03:09
[ASAP] Unsaturated Single Atoms on Monolayer Transition Metal Dichalcogenides for Ultrafast Hydrogen Evolution
by Yuting Luo†¶, Shuqing Zhang†¶, Haiyang Pan‡, Shujie Xiao§, Zenglong Guo?, Lei Tang†, Usman Khan†, Bao-Fu Ding†, Meng Li?, Zhengyang Cai†, Yue Zhao‡, Wei Lv§, Qingliang Feng?, Xiaolong Zou*†, Junhao Lin*?, Hui-Ming Cheng†#, and Bilu Liu*†
ACS Nano
DOI: 10.1021/acsnano.9b07763
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23 Dec 03:08
[ASAP] Inlaid ReS2 Quantum Dots in Monolayer MoS2
by Ziqian Wang†, Ruichun Luo†, Isaac Johnson†, Hamzeh Kashani†, and Mingwei Chen*†‡
ACS Nano
DOI: 10.1021/acsnano.9b08186
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23 Dec 03:05
[ASAP] Yu–Shiba–Rusinov States in the Charge-Density Modulated Superconductor NbSe2
by Eva Liebhaber†, Sergio Acero Gonza´lez‡, Rojhat Baba†, Gae¨l Reecht†, Benjamin W. Heinrich†, Sebastian Rohlf§, Kai Rossnagel§?, Felix von Oppen‡, and Katharina J. Franke*†
Nano Letters
DOI: 10.1021/acs.nanolett.9b03988
Xingxing Zhang, jingjiniao likes this
23 Dec 02:47
PdTe2 Transition‐Metal Dichalcogenide: Chemical Reactivity, Thermal Stability, and Device Implementation
by Gianluca D'Olimpio,
Cheng Guo,
Chia‐Nung Kuo,
Raju Edla,
Chin Shan Lue,
Luca Ottaviano,
Piero Torelli,
Lin Wang,
Danil W. Boukhvalov,
Antonio Politano
The chemical and thermal stability of PdTe2 is assessed by experiments and theory, with successive implementation in electronics. Remarkably, the responsivity of a PdTe2‐based millimeter‐wave receiver is 13 and 21 times higher than similar devices based on black phosphorus and graphene in the same operational conditions, respectively. Moreover, the PdTe2 surface is stable for one year, with only a sub‐nanometric TeO2 skin formed after air exposure.
Abstract
Palladium ditelluride (PdTe2) is a novel transition‐metal dichalcogenide exhibiting type‐II Dirac fermions and topological superconductivity. To assess its potential in technology, its chemical and thermal stability is investigated by means of surface‐science techniques, complemented by density functional theory, with successive implementation in electronics, specifically in a millimeter‐wave receiver. While water adsorption is energetically unfavorable at room temperature, due to a differential Gibbs free energy of ≈+12 kJ mol−1, the presence of Te vacancies makes PdTe2 surfaces unstable toward surface oxidation with the emergence of a TeO2 skin, whose thickness remains sub‐nanometric even after one year in air. Correspondingly, the measured photocurrent of PdTe2‐based optoelectronic devices shows negligible changes (below 4%) in a timescale of one month, thus excluding the need of encapsulation in the nanofabrication process. Remarkably, the responsivity of a PdTe2‐based millimeter‐wave receiver is 13 and 21 times higher than similar devices based on black phosphorus and graphene in the same operational conditions, respectively. It is also discovered that pristine PdTe2 is thermally stable in a temperature range extending even above 500 K, thus paving the way toward PdTe2‐based high‐temperature electronics. Finally, it is shown that the TeO2 skin, formed upon air exposure, can be removed by thermal reduction via heating in vacuum.
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23 Dec 02:44
[ASAP] Probing Angle-Dependent Interlayer Coupling in Twisted Bilayer WS2
by Wei Yan†§, Lan Meng‡§, Zhaoshun Meng†, Yakui Weng†, Lulu Kang†, and Xing-ao Li*†
The Journal of Physical Chemistry C
DOI: 10.1021/acs.jpcc.9b08602
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12 Dec 04:26
[ASAP] Band-Structure Spin-Filtering in Vertical Spin Valves Based on Chemical Vapor Deposited WS2
by Victor Zatko*†, Marta Galbiati†, Simon Mutien-Marie Dubois†§, Mauro Och?, Pawel Palczynski?, Cecilia Mattevi?, Pierre Brus†‡, Odile Bezencenet‡, Marie-Blandine Martin†, Bernard Servet‡, Jean-Christophe Charlier§, Florian Godel†, Aymeric Vecchiola†, Karim Bouzehouane†, Sophie Collin†, Fre´de´ric Petroff†, Bruno Dlubak*†, and Pierre Seneor*†
ACS Nano
DOI: 10.1021/acsnano.9b08178
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12 Dec 04:25
[ASAP] Spatially Controlled Fabrication and Mechanisms of Atomically Thin Nanowell Patterns in Bilayer WS2 Using in Situ High Temperature Electron Microscopy
by Jun Chen, Gyeong Hee Ryu, Qianyang Zhang, Yi Wen, Kuo-Lun Tai, Yang Lu, and Jamie H. Warner*
ACS Nano
DOI: 10.1021/acsnano.9b08220
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12 Dec 04:24
[ASAP] Synthesis of PdM (M = Zn, Cd, ZnCd) Nanosheets with an Unconventional Face-Centered Tetragonal Phase as Highly Efficient Electrocatalysts for Ethanol Oxidation
by Qinbai Yun‡§?, Qipeng Lu‡??, Cuiling Li‡??, Bo Chen‡, Qinghua Zhang#, Qiyuan He‡, Zhaoning Hu‡, Zhicheng Zhang‡, Yiyao Ge‡, Nailiang Yang‡?, Jingjie Ge‡, Yan-Bing He?, Lin Gu#%^, and Hua Zhang*†‡
ACS Nano
DOI: 10.1021/acsnano.9b07775
12 Dec 04:22
[ASAP] Fabrication and Imaging of Monolayer Phosphorene with Preferred Edge Configurations via Graphene-Assisted Layer-by-Layer Thinning
by Yangjin Lee†‡, Sol Lee†‡, Jun-Yeong Yoon†‡, Jinwoo Cheon‡§?, Hu Young Jeong*?, and Kwanpyo Kim*‡†
Nano Letters
DOI: 10.1021/acs.nanolett.9b04292
zhulj, Xingxing Zhang and -1 others like this
12 Dec 04:17
Graphene Nanoarchitectonics: Recent Advances in Graphene‐Based Electrocatalysts for Hydrogen Evolution Reaction
by Huajie Huang,
Minmin Yan,
Cuizhen Yang,
Haiyan He,
Quanguo Jiang,
Lu Yang,
Zhiyong Lu,
Ziqi Sun,
Xingtao Xu,
Yoshio Bando,
Yusuke Yamauchi
Electrode catalysts for the hydrogen evolution reaction are at the heart of electrochemical water splitting technology. Recent advances in the controllable synthesis, microstructural analysis, and electrocatalytic properties of graphene‐based hydrogen evolution electrocatalysts are presented, together with a discussion of the major challenges and opportunities in this emerging field.
Abstract
Under the double pressures of both the energy crisis and environmental pollution, the exploitation and utilization of hydrogen, a clean and renewable power resource, has become an important trend in the development of sustainable energy‐production and energy‐consumption systems. In this regard, the electrocatalytic hydrogen evolution reaction (HER) provides an efficient and clean pathway for the mass production of hydrogen fuel and has motivated the design and construction of highly active HER electrocatalysts of an acceptable cost. In particular, graphene‐based electrocatalysts commonly exhibit an enhanced HER performance owing to their distinctive structural merits, including a large surface area, high electrical conductivity, and good chemical stability. Considering the rapidly growing research enthusiasm for this topic over the last several years, herein, a panoramic review of recent advances in graphene‐based electrocatalysts is presented, covering various advanced synthetic strategies, microstructural characterizations, and the applications of such materials in HER electrocatalysis. Lastly, future perspectives on the challenges and opportunities awaiting this emerging field are proposed and discussed.
zhulj, Xingxing Zhang likes this
12 Dec 04:16
Phase Transition and Superconductivity Enhancement in Se‐Substituted MoTe2 Thin Films
by Peiling Li,
Jian Cui,
Jiadong Zhou,
Dong Guo,
Zhenzheng Zhao,
Jian Yi,
Jie Fan,
Zhongqing Ji,
Xiunian Jing,
Fanming Qu,
Changli Yang,
Li Lu,
Junhao Lin,
Zheng Liu,
Guangtong Liu
Consecutively tailoring few‐layer transition metal dichalcogenides from the 2H to Td phase may realize the long‐sought topological superconductivity by incorporating the quantum spin Hall effect and superconductivity. This study demonstrates that the transitions from Td to 1T' to 2H phase can be realized in Se‐substituted MoTe2 thin films. More importantly, the observed superconductivity enhancement can be interpreted as two‐band superconductivity.
Abstract
Consecutively tailoring few‐layer transition metal dichalcogenides MX2 from 2H to T d phase may realize the long‐sought topological superconductivity in a single material system by incorporating superconductivity and the quantum spin Hall effect together. Here, this study demonstrates that a consecutive structural phase transition from T d to 1T′ to 2H polytype can be realized by increasing the Se concentration in Se‐substituted MoTe2 thin films. More importantly, the Se‐substitution is found to dramatically enhance the superconductivity of the MoTe2 thin film, which is interpreted as the introduction of two‐band superconductivity. The chemical‐constituent‐induced phase transition offers a new strategy to study the s+− superconductivity and the possible topological superconductivity, as well as to develop phase‐sensitive devices based on MX2 materials.
12 Dec 04:15
Direct Visualization of Exciton Transport in Defective Few‐Layer WS2 by Ultrafast Microscopy
by Huan Liu,
Chong Wang,
Zhengguang Zuo,
Dameng Liu,
Jianbin Luo
Defect‐limited exciton transport in defective few‐layer WS2 is directly visualized by ultrafast microscopy. Neutral excitons can be captured by defects to form bound excitons in 7.75–17.88 ps, leading to decreased exciton lifetime and diffusion coefficient. Compared with the pristine sample, the exciton transport length of the defective sample is dramatically reduced from 349.44 to 107.40 nm.
Abstract
As defects usually limit the exciton diffusion in 2D transition metal dichalcogenides (TMDCs), the interaction knowledge of defects and exciton transport is crucial for achieving efficient TMDC‐based devices. A direct visualization of defect‐modulated exciton transport is developed in few‐layer WS2 by ultrafast transient absorption microscopy. Atomic‐scale defects are introduced by argon plasma treatment and identified by aberration‐corrected scanning transmission electron microscopy. Neutral excitons can be captured by defects to form bound excitons in 7.75–17.88 ps, which provide a nonradiative relaxation channel, leading to decreased exciton lifetime and diffusion coefficient. The exciton diffusion length of defective sample has a drastic reduction from 349.44 to 107.40 nm. These spatially and temporally resolved measurements reveal the interaction mechanism between defects and exciton transport dynamics in 2D TMDCs, giving a guideline for designing high‐performance TMDC‐based devices.
zhulj, Xingxing Zhang likes this
12 Dec 04:14
A New Opportunity for 2D van der Waals Heterostructures: Making Steep‐Slope Transistors
by Juan Lyu,
Jing Pei,
Yuzheng Guo,
Jian Gong,
Huanglong Li
2D materials are predicted to be a rich library of cold‐source (CS) materials. Transistors based on 2D metallic CS material:2D semiconducting channel material van der Waals (vdW) heterostructures can have steep subthreshold‐slopes below 60 mV dec−1 because of the multiple inherent advantages of the 2D vdW heterostructures, namely desired density‐of‐states–energy relations and gate‐tunable barrier heights.
Abstract
The use of a foreign metallic cold source (CS) has recently been proposed as a promising approach toward the steep‐slope field‐effect‐transistor (FET). In addition to the selection of source material with desired density of states–energy relation (D(E)), engineering the source:channel interface for gate‐tunable channel‐barrier is crucial to CS‐FETs. However, conventional metal:semiconductor (MS) interfaces generally suffer from strong Fermi‐level pinning due to the inevitable chemical disorder and defect‐induced gap states, precluding the gate tunability of the barriers. By comprehensive materials and device modeling at the atomic scale, it is reported that 2D van der Waals (vdW) MS interfaces, with their atomic sharpness and cleanness, can be considered as general ingredients for CS‐FETs. As test cases, InSe‐based n‐type FETs are studied. It is found that graphene can be spontaneously p‐type doped along with slightly opened bandgap around the Dirac‐point by interfacing with InSe, resulting in superexponentially decaying hot carrier density with increasing n‐type channel‐barrier. Moreover, the D(E) relations suggest that 2D transition‐metal dichalcogenides and 2D transition‐metal carbides are a rich library of CS materials. Graphene, Cd3C2, T‐VTe2, H‐VTe2, and H‐TaTe2 CSs lead to subthreshold swing below 60 mV dec−1. This work broadens the application potentials of 2D vdW MS heterostructures and serves as a springboard for more studies on low‐power electronics based on 2D materials.
12 Dec 03:22
Construction of Chiral, Helical Nanoparticle Superstructures: Progress and Prospects
by Soumitra Mokashi‐Punekar,
Yicheng Zhou,
Sydney C. Brooks,
Nathaniel L. Rosi
Helical nanoparticle superstructures are an exciting subclass of chiral nanomaterials with interesting chiroptical properties. The emergence and recent growth of this field is detailed, focusing on the various assembly methods developed for fabricating these unique materials.
Abstract
Chiral nanoparticle (NP) superstructures, in which discrete NPs are assembled into chiral architectures, represent an exciting and growing class of nanomaterials. Their enantiospecific properties make them promising candidates for a variety of potential applications. Helical NP superstructures are a rapidly expanding subclass of chiral nanomaterials in which NPs are arranged in three dimensions about a screw axis. Their intrinsic asymmetry gives rise to a variety of interesting properties, including plasmonic chiroptical activity in the visible spectrum, and they hold immense promise as chiroptical sensors and as components of optical metamaterials. Herein, a concise history of the foundational conceptual advances that helped define the field of chiral nanomaterials is provided, and some of the major achievements in the development of helical nanomaterials are highlighted. Next, the key methodologies employed to construct these materials are discussed, and specific merits that are offered by each assembly methodology are identified, as well as their potential disadvantages. Finally, some specific examples of the emerging applications of these materials are discussed and some areas of future development and research focus are proposed.
Xingxing Zhang likes this
12 Dec 03:22
DNA‐ and Field‐Mediated Assembly of Magnetic Nanoparticles into High‐Aspect Ratio Crystals
by Sarah S. Park,
Zachary J. Urbach,
Chase A. Brisbois,
Kelly A. Parker,
Benjamin E. Partridge,
Taegon Oh,
Vinayak P. Dravid,
Monica Olvera de la Cruz,
Chad A. Mirkin
DNA programmable assembly in combination with applied magnetic fields is used to direct magnetite nanoparticles into high‐aspect‐ratio superlattice crystals with various morphologies. A range of field strengths, nanoparticle core diameters, particle symmetries, and DNA lengths are explored to understand the competition between hybridization and magnetic dipole–dipole coupling interactions.
Abstract
Under an applied magnetic field, superparamagnetic Fe3O4 nanoparticles with complementary DNA strands assemble into crystalline, pseudo‐1D elongated superlattice structures. The assembly process is driven through a combination of DNA hybridization and particle dipolar coupling, a property dependent on particle composition, size, and interparticle distance. The DNA controls interparticle distance and crystal symmetry, while the magnetic field leads to anisotropic crystal growth. Increasing the dipole interaction between particles by increasing particle size or external field strength leads to a preference for a particular crystal morphology (e.g., rhombic dodecahedra, stacked clusters, and smooth rods). Molecular dynamics simulations show that an understanding of both DNA hybridization energetic and magnetic interactions is required to predict the resulting crystal morphology. Taken together, the data show that applied magnetic fields with magnetic nanoparticles can be deliberately used to access nanostructures beyond what is possible with DNA hybridization alone.
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12 Dec 03:19
Controlled Growth and Thickness‐Dependent Conduction‐Type Transition of 2D Ferrimagnetic Cr2S3 Semiconductors
by Fangfang Cui,
Xiaoxu Zhao,
Junjie Xu,
Bin Tang,
Qiuyu Shang,
Jianping Shi,
Yahuan Huan,
Jianhui Liao,
Qing Chen,
Yanglong Hou,
Qing Zhang,
Stephen J. Pennycook,
Yanfeng Zhang
The thickness‐tunable synthesis of rhombohedral Cr2S3 flakes is first achieved via a facile chemical vapor deposition route by a unique design of the metal precursor and a precise control of the growth temperature. Particularly, the conduction behavior of the nanothick Cr2S3 is variable with increasing thickness, i.e., from p‐type to ambipolar, and then to n‐type.
Abstract
2D magnetic materials have attracted intense attention as ideal platforms for constructing multifunctional electronic and spintronic devices. However, most of the reported 2D magnetic materials are mainly achieved by the mechanical exfoliation route. The direct synthesis of such materials is still rarely reported, especially toward thickness‐controlled synthesis down to the 2D limit. Herein, the thickness‐tunable synthesis of nanothick rhombohedral Cr2S3 flakes (from ≈1.9 nm to tens of nanometers) on a chemically inert mica substrate via a facile chemical vapor deposition route is demonstrated. This is accomplished by an accurate control of the feeding rate of the Cr precursor and the growth temperature. Furthermore, it is revealed that the conduction behavior of the nanothick Cr2S3 is variable with increasing thickness (from 2.6 to 4.8 nm and >7 nm) from p‐type to ambipolar and then to n‐type. Hereby, this work can shed light on the scalable synthesis, transport, and magnetic properties explorations of 2D magnetic materials.
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12 Dec 03:18
Large‐Scale Synthesis of Strain‐Tunable Semiconducting Antimonene on Copper Oxide
by Tianchao Niu,
Qingling Meng,
Dechun Zhou,
Nan Si,
Shuwei Zhai,
Xiamin Hao,
Miao Zhou,
Harald Fuchs
High‐quality antimonene with semiconducting nature is fabricated by molecular beam epitaxy on a dielectric oxide substrate. The evolution process and strain‐tunable band structures are revealed by scanning tunneling (ST) microscopy/ST spectroscopy measurements and theoretical calculations. The oxide substrate allows both decoupled electronic properties and direct integration of 2D systems into well‐established fabrication lines, a great advantage for large‐scale synthesis and practical application.
Abstract
Controlled synthesis of 2D structures on nonmetallic substrate is challenging, yet an attractive approach for the integration of 2D systems into current semiconductor technologies. Herein, the direct synthesis of high‐quality 2D antimony, or antimonene, on dielectric copper oxide substrate by molecular beam epitaxy is reported. Delicate scanning tunneling microscopy imaging on the evolution intermediates reveals a segregation growth process on Cu3O2/Cu(111), from ordered dimer chains to packed dot arrays, and finally to monolayer antimonene. First‐principles calculations demonstrate the strain‐modulated band structures in antimonene, which interacts weakly with the oxide surface so that its semiconducting nature is preserved, in perfect agreement with spectroscopic measurements. This work paves the way for large‐scale growth and processing of antimonene for practical implementation.
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