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Surface-Condition-Dependent Deformation Mechanisms in Lead Nanocrystals

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Research 2022年第4期2022卷 589-595页

作者： Hongtao Zhangg Wen Wang Jun sun Li Zhong Longbing He litao sun SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSoutheast UniversityNanjing 210096China Center for Advanced Materials and Manufacture Southeast University-Monash University Joint Research InstituteSuzhou215123China

Serving as nanoelectrodes or frame units,small-volume metals may critically affect the performance and reliability of nanodevices,especially with feature sizes down to the nanometer ***-volume metals usually behave extraordinarily in comparison with their bulk counterparts,but the knowledge of how their sizes and surfaces give rise to their extraordinary properties is currently *** this study,we investigate the influence of surface conditions on mechanical behaviors in nanometer-sized Pb crystals by performing in situ mechanical deformation tests inside an aberration-corrected transmission electron microscope(TEM).Pseudoelastic deformation and plastic deformation processes were observed at atomic precision during deformation of pristine and surface-oxidized Pb particles,*** is found that in most of the pristine Pb particles,surface atom diffusion dominates and leads to a pseudoelastic deformation *** stark contrast,in surface-passivated Pb particles where surface atom diffusion is largely inhibited,deformation proceeds via displacive plasticity including dislocations,stacking faults,and twinning,leading to dominant plastic deformation without any *** research directly reveals the dramatic impact of surface conditions on the deformation mechanisms and mechanical behaviors of metallic nanocrystals,which provides significant implications for property tuning of the critical components in advanced nanodevices.

关键词： deformation sizes diffusion

In Situ Liquid Cell Transmission Electron Microscopy Observations of Growth and Anticorrosion Behaviors of AuCl3 Shell on Au Nanobipyramids

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Chinese Journal of Chemistry 2024年第22期42卷 2757-2764页

作者： Wei Wei Jun sun Songtao Zhang litao sun Feng Xu School of Information Technology Jiangsu Open UniversityNanjingJiangsu 210036China SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationCollaborative Innovation Center for Micro/Nano FabricationDevice and SystemSoutheast UniversityNanjingJiangsu 210096China Testing Center Yangzhou UniversityYangzhouJiangsu 225009China

Comprehensive Summary Designing new materials and architectures to maintain activity and stability requires a better understanding on the anticorrosion dynamics of ***-coordinated atoms on the surface of nanoparticles can be protected by deposited ***-time observation on how protective shells grow and play a role is challenging but ***,protective effects of AuCl_(3) shells on Au nanobipyramids(NBPs)are studied in HAuCl_(4) aqueous solutions by in-situ liquid cell transmission electron microscopy(LCTEM).This study is the first to observe the formation of Au-AuCl_(3) core-shell nanostructure and the corresponding anticorrosion behaviors of AuCl_(3) deposited *** presence of CTAB can substantially influence the growth mode and structure of AuCl_(3) shell,by a direct or indirect way,intervene the dissolution of Au *** growth or dissolution kinetics here revealed at the nanoscale provide insights towards engineering of the surface anticorrosion to pursue Au nanoparticles with improved stability in acidic environment.

关键词： In situ liquid cell TEM Au-AuCl core-shell Growth process Anticorrosion behavior I Nanotechnology Synthesis design Crystalstructure

Atomic-scale insights into the formation of 2D crystals from in situ transmission electron microscopy

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Nano Research 2021年第6期14卷 1650-1658页

作者： Yatong Zhu Dundong Yuan Hao Zhang Tao Xu litao sun SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSoutheast UniversityNanjing210096China Center for Advanced Materials and Manufacture Southeast University-Monash University Joint Research InstituteSuzhou215123China

Two-dimensional(2D)crystals are attractive due to their intriguing structures and properties which are strongly dependent on the synthesis *** achieve their superior properties,it is of critical importance to fully understand the growth processes and mechanisms for tailored design and controlled growth of 2D *** to the high spatiotemporal resolution and the capability to mimic the realistic growth conditions,in situ transmission electron microscopy(TEM)becomes an effective way to monitor the growth process in real-time at the atomic scale,which is expected to provide atomic-scale insights into the nucleation and growth of 2D *** we review the recent in situ TEM works on the formation of 2D crystals under electron irradiation,thermal excitation as well as voltage *** underlying mechanisms are also elucidated in detail,providing key insights into the nucleation and formation of 2D crystals.

关键词： two-dimensional crystal in situ transmission electron microscopy formation mechanism electron irradiation

Phase transformation at controlled locations in nanowires by in situ electron irradiation

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Nano Research 2020年第7期13卷 1912-1919页

作者： Hongtao Zhang Wen Wang Tao Xu Feng Xu litao sun SEU-FEI Nano-Pico Center Key Laboratory ofMEMS of Ministry of EducationSoutheast UniversityNanjing 210096China Center for Advanced Materials and Manufacture Southeast University-Monash University Joint Research InstituteSuzhou 215123China

Solid state phase transtormations have drawn great attention because they can be effectively exploited to control the microstructure and property of *** the physics of such phase transformation processes is critical to designing materials with controlled structure and with desired ***,in traditional ex situ experiments,it is hard to achieve position controlled phase transformations or obtain desirable crystal phase on nanometer *** the underlying mechanisms of the reaction processes are not fully understood due to the lack of direct and real-time *** this paper,we observe phase transformation from body-centered tetragonal PX PbTiO3 to monclinic TiO2(B)on the atomic scale by in situ electron iradiation during heat treatment in transmission electron microscope,at pre-defined locations on the *** demonstrate that by controlling the location of the incident electron beam,a porous TiO2(B)crystal structure can be formed at the desired area on the nanowire,which is dificult to achieve by traditional synthesis *** in situ heating,the Pb atoms in the crystal migrate out of the pristine nanowire through inelastic scattering under incident electrons while high temperature(>400℃)provides energy for the crytalization of TiO2(B)and the vlatlization of a substantial number of Pb atoms,which makes the resultingTiO2(B)nanowires to be *** contrast,at temperatures<400℃,the segregated Pb atoms form Pb particles and the TiO、nanowires remain in the amorphous *** work not only provides in situ visualization of the phase transition from the PX-PbTiO3 to monoclinic TiO2(B),but also suggests a crystallography engineering strategy to obtain the desired crystal phase at controlled locations on the nanometer scale.

关键词： phase transformation controlled locations in situ transmission electron microscopy

Defect Engineering in 2D Materials: Precise Manipulation and Improved Functionalities

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Research 2019年第1期2019卷 42-55页

作者： Jie Jiang Tao Xu Junpeng Lu litao sun Zhenhua Ni School of Physics Southeast UniversityNanjing 211189China SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSoutheast UniversityNanjing 210096China

Two-dimensional(2D)materials have attracted increasing interests in the last *** ultrathin feature of 2D materials makes them promising building blocks for next-generation electronic and optoelectronic *** reducing dimensionality from 3D to 2D,the inevitable defects will play more important roles in determining the properties of *** order to maximize the functionality of 2D materials,deep understanding and precise manipulation of the defects are *** the recent years,increasing research efforts have been made on the observation,understanding,manipulation,and control of defects in 2D ***,we summarize the recent research progress of defect engineering on 2D *** defect engineering triggered by electron beam(e-beam),plasma,chemical treatment,and so forth is comprehensively ***,e-beam irradiation-induced defect evolution,structural transformation,and novel structure fabrication are *** the assistance of a high-resolution electron microscope,the dynamics of defect engineering can be visualized in ***,defect engineering employed to improve the performance of 2D devices by means of other methods of plasma,chemical,and ozone treatments is *** last,the challenges and opportunities of defect engineering on promoting the development of 2D materials are *** this review,we aim to build a correlation between defects and properties of 2D materials to support the design and optimization of high-performance electronic and optoelectronic devices.

关键词： materials defect treatment

Enhancing stability by tuning element ratio in 2D transition metal chalcogenides

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Nano Research 2021年第6期14卷 1704-1710页

作者： Zhenjia Zhou Tao Xu Chenxi Zhang Shisheng Li Jie Xu litao sun Libo Gao National Laboratory of Solid State Microstructures School of PhysicsCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210093China SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSchool of Electronic Science and EngineeringSoutheast UniversityNanjing210096China International Center for Young Scientists(ICYS) National Institute for Materials Science(NIMS)TsukubaIbaraki3050044Japan

Two-dimensional(2D)transition metal chalcogenides(TMCs)are known to be susceptible to the atmosphere,which greatly obscures the intrinsic physical and chemical *** quantitative origin of the instability on the atomic scale has not been well investigated due to the lack of environmentally stable TMCs ***,we find the stability of the grown TMCs is strongly relevant to their initial element ratios,and thus the stoichiometric bonded TMCs have favorable stability,benefitted from the TMCs with controllable *** this study,the degree of structural degradation has been quantitatively defined by the reduced element ratio of chalcogen to metal through the time-dependent characterizations,and the non-stoichiometric ratios in TMCs reveal the atomic lattices with point defects like additive bonds or vacancies *** study not only provides a potential view to fabricate environmentally stable TMCs based devices,but also will bring an effective feasibility of stacking stable vertical heterostructures.

关键词： transition metal chalcogenides stability point defects stoichiometric ratio two-step vapor deposition

Thermal stability of Te nanowires and their crystallographydetermined surface evolution at elevated temperatures

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Nano Research 2023年第4期16卷 5695-5701页

作者： Lei Shangguan Yating Ran Ziyu Lu Yutian Gao Lei Shi Longbing He litao sun SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSoutheast UniversityNanjing 210096China Centre for Advanced Materials and Manufacture Joint Research Institute of Southeast University and Monash UniversitySuzhou 215123China

Nanowires are fantastic nanostructures for designing new functional devices because of their extraordinary ***,nanowires usually suffer pronounced size and surface effects with decreasing diameter *** their structure and thermal stability can still fill the requirements of practical applications is a critical issue to be figured ***,Te nanowires with diameters ranging from sub-10 to over 80 nm are used as samples to probe into this *** situ heating experiments are performed on these Te nanowires using an aberration-corrected transmission electron microscopy combined with a chip-based heating *** is found that Te nanowires suffer sublimation at elevated temperatures rather than melting,showing sizedependent sublimation *** Te nanowires with diameter smaller than 20 nm sublimate below 205℃,while the larger ones with diameter around 85 nm require a higher temperature of around 225℃.During sublimation-induced shape evolution,the interfacial wetting equilibrium and crystal orientations play critical roles,leading to the formation of spherical surfaces or featured facets at the free surfaces.A mean contact angle of 107.5°is determined at the C-Te interface when the crystalline Te nanowires stay in a quasi-liquid equilibrium ***,once the crystalline feature is overwhelming,e.g.,at moderate temperatures,the(1011),(1120),and(1010)facets govern the free surface,despite the wetting condition at the interfaces.

关键词： Te nanowires in situ transmission electron microscopy thermal stability surface evolution

Combining in-situ TEM observations and theoretical calculation for revealing the thermal stability of CeO_(2) nanoflowers

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Nano Research 2022年第2期15卷 1319-1326页

作者： Mingyun Zhu Kuibo Yin Yifeng Wen Shugui Song Yuwei Xiong Yunqian Dai litao sun SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSoutheast UniversityNanjing 210096China School of Chemistry and Chemical Engineering Southeast UniversityNanjing 211189China

The thermal stability of Ce_(2) nanomaterials can directly impact both the uniformity of the supported catalysts and the catalytic behavior of Ce_(2) ***,knowledge about the thermal stability of Ce_(2) is still ***,we conduct in-situ transmission electron microscopy experiments and theoretical calculations to elucidate the thermal stability of Ce_(2) nanomaterials under different environments.A sinter(700℃)are observed within Ce_(2) nanoflowers under O_(2).The sinter firstly occurs among the nanoflowers’monomers and then the sintered nanoparticles structurally decompose to tiny nanoparticles from the strain *** a vacuum environment,the Ce_(2) nanoflowers firstly undergo a transition from cubic fluorite Ce_(2) to hexagonal Ce_(2)O_(3),accompanied by the oxygen *** Ce_(2)O_(3) nanoparticles further atomically sublimate from the edges to the center under high *** calculation results reveal a considerably lower energy barrier for the structural decomposition under O_(2) and for the sublimation under *** work provides a perspective on the structural design and performance optimization of Ce_(2)-based catalysts.

关键词： CeO_(2) in-situ transmission electron microscopy structural evolution thermal stability theoretical calculation

Visualizing the crystallization of sodium chloride under supersaturated condition

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Nano Research 2024年第8期17卷 7786-7792页

作者： Mao Ye Tao Xu Yuwei Xiong Yatong Zhu Mingrui Zhou Longxiang Han Jinyi sun Ming Qin litao sun SEU-FEI Nano-Pico Center Key Laboratory of MEMS of Ministry of EducationSchool of Integrated CircuitsSoutheast UniversityNanjing 210096China

Crystallization in supersaturated solution plays a fundamental role in a variety of natural and industrial ***,a thorough understanding of crystallization phenomena in supersaturated solution is still difficult because the real-time visualization of crystallization processes under supersaturated condition is a great ***,an electron beam-induced crystallization method was carried out in in situ liquid cell transmission electron microscopy(TEM)to visualize the crystallization of NaCl under supersaturated condition in real *** steps and behaviors in the crystallization of NaCl were captured and clarified,including the growth of NaCl nanocrystals with different morphologies,the formation of initial crystalline seeds from amorphous ion clusters,and the non-equilibrium growth behaviors caused by uneven distribution of precursor *** study provides the real-time visualization of detailed nucleation and growth behaviors in NaCl crystallization and brings an ideal strategy for investigating crystallization phenomena under supersaturated condition.

关键词： crystallization in situ liquid cell transmission electron microscopy(TEM) electron-water interaction sodium chloride