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A deep understanding of the mechanisms controlling shear banding is of fundamental importance for improving the mechanical properties of metallic glasses. Atomistic simulations highlight the importance of nanoscale stresses and strains for shear banding, but corresponding experimental proofs are scarce due to limited characterization techniques. Here, by using precession nanodiffraction mapping in the transmission electron microscope, the atomic density and strain distribution of an individual shear band is quantitatively mapped at 2 nm resolution. We demonstrate that shear bands exhibit density alternation from the atomic scale to the submicron scale and complex strain fields exist, causing shear band segmentation and deflection. The atomic scale density alternation reveals the autocatalytic generation of shear transformation zones, while the density alternation at submicron scale results from the progressive propagation of shear band front and extends to the surrounding matrix, forming oval highly strained regions with density consistently higher (∼0.2%) than the encapsulated shear band segments. Through combination with molecular dynamic simulations, a complete picture for shear band formation and propagation is established.

In our work, NiCo2O4@Ni(OH)2 electrode materials are prepared by a two-step hydrothermal method. The synthesized product can be directly used as electrode material of a supercapacitor, and its specific capacity is 687 C g−1 at 1 A g−1. The composite electrode is used as the positive electrode and a hybrid capacitor is assembled. The ASCs (asymmetric supercapacitors) possess an energy density of 71.38 Wh kg−1 at a power density of 2750 W kg−1 and capacity retention of 92% after 10,000 cycles.

The viscoelastic behavior of four different bulk metallic glass (BMG) systems, i.e., Cu46Zr46Al8, Cu44Zr44Al8Co4, Cu44Zr44Al8Hf4, and Cu44Zr44Al8Co2Hf2, is investigated concerning its deformation-mode dependence via dynamic mechanical analysis (DMA) in 3-point bending (TPB), tension, and torsion modes. At temperatures below the glass transition, the considered BMGs deform primarily elastic, and the mechanical response is independent of the testing frequency, whereas, in the glass transition region, the viscoelastic component dominates. Crystallization decreases the viscoelastic contribution, whereas plastic deformation leads to an increase in atomic mobility for all three deformation modes. Compared to tension and torsion, TPB is found to be more sensitive to dynamic mechanical stress. TPB generates a complex stress state in the matrix and can thus introduce substantial variations in loss modulus. Structural analyses carried out by transmission electron microscopy and X-ray diffraction confirmed the amorphous nature of the base composition and structural changes when heated to the intermediate peak temperature observed at 743 K for the TPB mode. Compared to Cu46Zr46Al8, 4 at. pct Co addition in the Cu46−x\2Zr46−x\2Al8Cox amorphous alloy leads to a glass showing relatively higher thermomechanical stability around its glass transition. This study provides evidence for the enhancement of the mechanical properties of CuZr-based BMGs at elevated temperatures by microalloying.

Layered double hydroxides (LDHs) have lately been hailed as robust lubricant additives for improving tribological properties and as ideal catalysts for synthesizing carbon-based nanomaterials. In this paper, in situ analytical tools are used to track the evolution of the crystal structure and chemical composition of LDHs during calcination. Nickel oxide and elemental nickel can be produced by calcining NiAl-LDH in air (LDH-C-Air) and argon (LDH-C-Ar), respectively. For the base oil with 1 wt % LDH-C-Air, negligible wear can be detected even after a 2 h friction test under a severe contact pressure (∼637 MPa). A relatively thick tribofilm (∼60 nm) with a better mechanical property is formed, which protects the solid surface from severe wear. In addition, the possible formed carbon debris may also prevent the direct collision of asperities and effectively improve the wear resistance. This work provides a unique vision for the application of calcined LDHs with the combination of catalysis and tribology.

Knowledge regarding the phase and valence state evolution of molybdenum (Mo) and its oxides during the redox reaction is essential for advancing their energy applications (e.g., electrocatalysis), which unfortunately remains largely unexplored. Herein, the effects of atomic and electronic structures on the electrocatalytic performance of Mo/oxides core–shell structures are investigated on the basis of the combination of ex situ and in situ experiments. First, a two-step reaction pathway is revealed during the oxidation of nanoscale Mo: the formation of amorphous MoO3 (A-MoO3) shells followed by the nucleation of crystalline α-MoO3. It is shown that the electrocatalytic performance of A-MoO3 is superior to that of α-MoO3, mainly due to more catalytically active sites in the former material. Furthermore, in situ transmission electron microscopy observations show that the A-MoO3 shell can be rapidly reduced into metallic MoO2 under reductive environment, which is likely to occur during the hydrogen evolution...

Determining atomistic structures of grain boundaries (GBs) is essential to understand structure–property interplay in oxides. Here, different GB superstructures in CuO nanosheets, including $$(11\bar1)$$ and (114) twinning boundaries (TBs) and (002)/(223) GB, are investigated. Unlike the lower-energy stoichiometric $$(11\bar1)$$ TB, both experimental and first-principles investigations reveal a severe segregation of Cu and O vacancies and a nonstoichiometric property at (114) TB, which may facilitate ionic transportation and provide space for elemental segregation. More importantly, the calculated electronic structures have shown the increased conductivity as well as the unanticipated magnetism in both (114) TB and (002)/(223) GB. These findings could contribute to the race towards the property-directing structural design by GB engineering.

Silica supported Pd (∼2 nm), Pd3Fe (∼2 nm) and Pd3Fe_large (∼12 nm) catalysts were synthesized and tested for propane dehydrogenation at 510 °C. At the 10% conversion, Pd and Pd3Fe catalysts exhibited propylene selectivity of 45% and 94%, respectively. Moreover, the latter showed a turnover rate (TOR) of 0.2 s−1, which is five times higher than that of the Pd catalyst (0.04 s−1). Pd K edge XAS, XRD, and CO adsorbed IR were used to characterize the geometric structure of the catalysts. By combined comparison of XRD and XAS spectra of Pd3Fe and Pd3Fe_large catalysts, we successfully identified the crystalline phase in the 2 nm Pd3Fe catalyst. The CO adsorbed IR suggests that the formation of Pd3Fe breaks the ensemble of Pd, which is responsible for the increase of selectivity. The Pd L edge XAS was used to characterize the electronic structure of the catalysts. The Pd3Fe catalyst exhibits an increase of the edge energy compared with the Pd catalyst, which indicates the change of d-band structure in the bimetallic catalyst. The change in the electronic structure is likely the reason for the increase in TOR.

With the increasing requirement of developing non-toxic piezoelectric materials, an alkaline niobate-based perovskite solid (K,Na)NbO3 (KNN) has been intensively studied. Promising piezoelectric properties are reported, which are mostly achieved by adding other elements, or simply varying the K/Na ratio. It is found that KNN nanorods grown on conductive Nb-doped SrTiO3 (STO) substrates show enhanced piezoelectric properties after annealing at 800 °C for 12 h [Y. He, Z. Wang, W. Jin, X. Hu, L. Li, Y. Gao, X. Zhang, H. Gu and X. Wang, Appl. Phys. Lett., 2017, 110, 212904]. However, the underlying mechanism for property enhancement at the atomic scale is not clearly revealed. In this study, comprehensive transmission electron microscopy techniques are utilized focusing on the atomic scale study of the interfacial composition, structures, strain, dipolar displacement vectors and their variations along the interface normal of the as-grown and annealed KNN nanorods. The results indicate phase transformation during annealing, and a larger spontaneous polarization within each unit cell of the annealed KNN nanorods, which lead to an overall enhancement of the piezoelectric properties. These results would be very beneficial for advanced nanogenerators and sensors with enhanced piezoelectric properties.

Semiconducting binary sulfides are often produced with controlled size and shape by solvothermal synthesis using amine solvents. The versatility of this method, however, has not been extended to dense ternary sulfides that include alkali and transition metal ions, which are renowned for their complex magnetic and electronic properties. We report the solvothermal synthesis of the alkali–transition metal sulfides KFeS2 and KFe2S3. The latter compound is not accessible by direct solid-state synthesis. Magnetic susceptibility measurements indicate antiferromagnetic ordering of KFeS2 and KFe2S3, which contain single and double chains of FeS4 tetrahedra, respectively. Given the ability to access KFe2S3 here, further development of this method may lead to isolation of new functional compounds.

Depending on the nucleation sites, two types of tin dioxide (SnO2) nanostructures were synthesized: (1) single-crystal SnO2 nanowires and (2) novel tri-crystal SnO2 nanobelts with the coexistence of (301) and (01) twins. It is speculated that the different vapor concentrations of Sn/O may lead to the nucleation of distinct structures and morphologies in low-dimensional SnO2. Meanwhile, the growth direction changes in both nanowires (from [01] to [001]) and nanobelts (from [03] to [001]), which could be related to the relatively lower Sn/O ratio during the later growth stages. The thermodynamic growth processes are also discussed in terms of surface energy. These findings contribute to the intuitive understanding of the growth mechanisms in SnO2 which may lead to the property-controlled design of next generation optical and electrical nanodevices.

Here we provide a systematic study of tensile deformation mechanisms in PdSi metallic glasses employing polymer-supported sputter deposited films. Due to the polymer substrate, global strain localization within one critical shear band is inhibited and thus thousands of different shear bands and cracks can be examined within a single tensile sample. Two distinctly different types of shear bands, allowed by the sample geometry, are observed and analyzed. It is shown that crack formation occurs through activation of multiple out-of-plane shear bands leading to local plasticity and neck-like shape of crack edges. The in-plane shear bands, which appear at higher applied strains, typically do not lead to crack formation and can accommodate both applied tensile strain and transverse compressive strain. The mechanism of effective strain hardening through de-activation of in-plane shear bands is demonstrated by means of quasi-in-situ studies. Shear banding is shown to be the fundamental deformation mechanism for different film thicknesses ranging from 25 to 1000 nm. Polymer-supported films represent a unique model material system which enables easy characterization of the tensile behavior of metallic glasses and provides an opportunity to gain new insights into the fundamental mechanisms of shear banding.

Atomic-scale oxidation dynamics of Cu2O nanocrystallines (NCs) are directly observed by in situ high-resolution transmission electron microscopy. A two-stage oxidation process is observed: (1) The initial oxidation stage is dominated by the dislocation-mediated oxidation behavior of Cu2O NCs via solid-solid transformations, leading to the formation of a new intermediate CuO x phase. The possible crystal structure of the CuO x phase is discussed. (2) Subsequently, CuO x is transformed into CuO by layer-by-layer oxidation. These results will help in understanding the oxidation mechanisms of copper oxides and pave the way for improving their structural diversity and exploiting their potential industrial applications.

Employing electrons for direct control of a nanoscale reaction is highly desirable since it enables fabrication of nanostructures with different properties at atomic resolution and with flexibility of dimensions and location. Here, applying in situ transmission electron microscopy, we show the reversible oxidation and reduction kinetics in Ag, well controlled by changing the dose rate of the electron beam. Aberration-corrected high-resolution transmission electron microscopy observation reveals that O atoms are preferably inserted and extracted along the {111} close-packed planes of Ag, leading to the nucleation and decomposition of nanoscale Ag2O islands on the Ag substrate. By controlling the electron beam size and dose rate, we demonstrated the fabrication of an array of 3 nm Ag2O nanodots in an Ag matrix. Our results open a new pathway to manipulate an atomistic reaction with an electron beam towards the precise fabrication of nanostructures for device applications.

Although coherent twin boundary (CTB) migration in fcc metals has been widely studied, little is known about the CTB migration behavior in the binary transition-metal nitrides system (e.g. rock-salt CrN). Using in-situ atomic-resolution electron microscopy, we report two different twin boundary defect (TD) nucleation and CTB migration modes at the CTB/ITB (incoherent twin boundary) and CTB/surface junctions. A new twin defect nucleation and CTB migration mode are observed from the CTB/surface junction. We show that such CTB migration is associated with a boundary structure alternating from an N-terminated to Cr-terminated, involving Cr and N atom respective motion, i.e., asynchronous CTB migration. We further reveal the dynamic and thermodynamic mechanism of such asynchronous migration through strain analysis and DFT simulations. Our findings uncover an atomic-scale dynamic process of defect nucleation and CTB migration in a binary system, which provides new insight into the atomic-scale deformation mechanism in complex materials.

Defects, such as dislocations, grain boundaries, and surfaces, play vital roles in the properties of nanocrystalline metal oxides. Thus, it is crucial to understand the structural evolution during the growth of metal oxides. In this work, atomistic observation of the structural dynamics in MgO grains during magnesium oxidation is realized by the in situ high resolution transmission electron microscopy. There are three major equivalent orientation relationships between MgO grains and Mg. Interestingly, our experiments reveal the grain rotation and grain boundary (GB) migration, resulting in the change of the orientation in MgO grains and the morphology of GBs. The dislocation activity that may mediate the GB migration and/or grain rotation is captured in MgO with high lattice strain/stress. Our results provide the atomic-scale structural evolution of the growth of passivating oxide layer on the Mg surface, which not only facilitate the development of metal oxide growth method but also provide a possible an...

An effective way to modify the photocatalytic activity of both anatase and rutile TiO2 nanoparticles by coating the surface with either an inorganic (SiO2/silica) or organic (green-tea) layer using a chemical approach is demonstrated. Tetraethyl orthosilicate (TEOS) was used to cover the surface of TiO2 with silica which facilitates the inhibition of photocatalytic activity, ensuring its application in sunscreens by blocking the reactive oxygen species (ROS). Green-tea extract, rich in epigallocatechin gallate (EGCG), was used to coat/stabilize nano-sized TiO2. The morphology of these coatings was revealed by transmission electron microscopy (TEM) and by energy dispersive spectroscopy (EDS) mapping. These studies showed good coverage for both types of coating, but with somewhat better uniformity of the coating layer on rutile TiO2 compared to anatase due to its more uniform particle geometry. The effectiveness of each coating was evaluated by photodegradation of an organic dye (methyl orange). These studies showed rutile_polyphenol exhibits the highest photocatalytic activity among rutile forms which validates its feasibility to be used in photodegradation.

The structural characteristics of monoclinic CuO nanowires (NWs) fabricated by heating pure Cu in ambient air were investigated by electron microscopy. Besides the single-crystalline NW, four different twinned NWs with twinning planes of (11\bar 1), (002), (110) and {{(20\bar 2)}} have been found. The twin boundaries are generally in parallel with the NW axial direction. To the best of the authors' knowledge, the {{(11\bar 1)}} and (110) twins are reported for the first time in CuO. Moreover, the prevailing existence of {{(11\bar 1)}} and (002) twinned NWs could be closely related to the NW growth as well as the oxidation processes of Cu. The presented results provide a systematic investigation on the twin structures of CuO NWs, which may open up a pathway to explore new potential applications of CuO nanostructures.

Metal-organic framework (MOF)-derived materials have attracted increasing interest and show promising catalytic performances in many fields. Intensive efforts have been focused on the structure design and metal-site integration in MOF-derived catalysts. However, the key catalytic processes related with the metal sites in MOF-derived catalysts that dominate the electrocatalytic performance still remain obscure. Herein, we show a neglected but critical issue in the pyrolytic synthesis of MOF-derived catalysts: the coupled evolution of dual sites, that is, metallic sites and single-atom metal sites. The identification of active sites of single-atom sites from the visible particles has been elucidated through the combined X-ray spectroscopic, electron microscopic, and electrochemical studies. Interestingly, after a total removal of metallic cobalt sites, catalysts with purified single-atom metal sites show no faltering activity for either the oxygen reduction reaction (ORR) or hydrogen evolution reaction (HER), while significantly enhanced ORR selectivity is achieved; this reveals the dominant activity and selectivity contribution from single-atom electrocatalysis. The insight of the coupled evolution of dual sites and the as-demonstrated dual-site decoupling strategies open up a new routine for the design and synthesis of MOF-derived catalysts with the optimized single-atom electrocatalysis towards various electrochemical reactions.

Unraveling the phase selection mechanisms of semiconductor nanowires (NWs) is critical for the applications in future advanced nanodevices. In this study, the atomistic vapor–solid–liquid growth processes of Sn-catalyzed wurtzite (WZ) and zinc blende (ZB) ZnO are directly revealed based on the in situ transmission electron microscopy. The growth kinetics of WZ and ZB crystal phases in ZnO appear markedly different in terms of the NW–droplet interface, whereas the nucleation site as determined by the contact angle ϕ between the seed particle and the NW is found to be crucial for tuning the NW structure through combined experimental and theoretical investigations. These results offer an atomic-scale view into the dynamic growth process of ZnO NW, which has implications for the phase-controllable synthesis of II–VI compounds and heterostructures with tunable band structures.

This paper presents an electron microscopy study of reduced calcium titanate crystals (CaTi2O4) and the growth mechanism of titanium monoxide TiOxon a CaTi2O4surface. Large high-quality CaTi2O4crystals were prepared using the molten salt flux method. The crystallographic directions and the growth direction of the CaTi2O4crystalline needles were confirmed by electron backscatter diffraction and Kikuchi pattern analysis. The low-angle grain boundaries in CaTi2O4and the crystallographic orientation relationship between CaTi2O4and TiOxwere investigated using high-resolution transmission electron microscopy. It is found that both the low-angle boundaries and the amorphous area may play a key role during the growth process of titanium monoxide TiOx. The results presented here contribute to a better understanding of the detailed growth mechanism of TiOxon a CaTi2O4surface.

The mechanical behavior of CuO nanowires (NWs) was investigated by in situ transmission electron microscopy. During compression, the NWs exhibited high bending capabilities associated with high mechanical stress. Interestingly, anelasticity was consistently observed after stress release. Further investigations indicate that the anelasticity is intrinsic to the CuO NWs, although electronbeam irradiation was proved capable of accelerating the shape recovery. A mechanism based on the cooperative motion of twin-associated atoms is proposed to account for this phenomenon. The results provide insight into the mechanical properties of CuO NWs, which are promising materials for nanoscale damping systems.

International audience; The detailed study of phase transition processes among various calcium sulfates is still insufficient in spite of its importance in artificial and natural processes. Here, the phase transformation γ-CaSO4 → β-CaSO4 → CaO is induced by electron beam irradiation and directly observed inside the transmission electron microscope (TEM). Relying on the real-time atomic-scale observation, the topological transition from γ-CaSO4 (hexagonal) to β-CaSO4 (orthorhombic) is investigated in detail, and the orientation relationship is determined: [0001]H//[001]O and (101̅0)H//(010)O. Furthermore, three β-CaSO4 variants related by 120° rotation are observed, which is theorized to occur during the transformation from hexagonal to orthorhombic structure. The possible transition mechanism is thus discussed. This work offers detailed information on the transition mechanism concerning the calcium sulfates, which might facilitate their industrial applications and possibly further understanding of rock deformation in the earth crust.

Highlights: • Cu nanoparticles were synthesized on the surface of carbon nanotubes by heating. • The particle size could be tuned by controlling the temperature and duration. • The possible nucleation and growth mechanisms of nanoparticles were discussed. - Abstract: In this paper, employing simple heating inside the transmission electron microscope, we demonstrated the decoration of carbon nanotubes (CNTs) by Cu nanoparticles (NPs). More significantly, the particle sizes could be effectively controlled by simply controlling the temperature and duration. It is believed that the nucleation and growth of NPs results from the deposition of generated Cu vapor as well as the surface diffusion of Cu on the CNTs at elevated temperature.

Layered double hydroxides (LDHs) are a class of naturally occurring inorganic minerals that are composed of divalent and trivalent metal cations. In this study, three different sized NiAl-LDH nanoplatelets were synthesized by varying crystallization time during the microemulsification process. The layered structure and three-dimensional size of nanoplatelets were confirmed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). As lubricant additives, their tribological properties in base oil were evaluated by use of a ball-on-disk reciprocating tribometer under three different loads: 50, 100, and 150 N (which created peak Hertz pressures of 1.74, 2.16, and 2.47 GPa). Under contact pressures of up 2.16 GPa, not only did the coefficient of friction (COF) decrease by about 10% after nano-LDHs were added but also the wear performance improved substantially. These improvements resulted from a protective tribolayer formation on the contact interface, as revealed by detailed surface and structure analytical studies. In particular, cross-sectional TEM images revealed that the larger size nanoplatelets (NiAl-24h), rather than the smaller ones (NiAl-6h) showed the best and most stable tribological performance. This was mainly because of their higher degree of crystallinity, which in turn resulted in the formation of a tribofilm with far superior mechanical properties during sliding. Owing to the simple synthetic method and superior tribological properties as oil-based additives, nano-LDHs hold great potential for use in demanding industrial applications in the future.

We observed the dynamic evolution of the morphology and phase transformations of CuO nanowires during sodiation using in situ transmission electron microscopy. These results will facilitate our fundamental understanding of the sodiation mechanism of CuO nanostructures used as electrode materials in sodium ion batteries.

Fractals are commonly observed in nature and elucidating the mechanisms of fractal-related growth is a compelling issue for both fundamental science and technology. Here we report an in situ electron microscopy study of dynamic fractal growth of platinum during electrodeposition in a miniaturized electrochemical cell at varying growth conditions. Highly dendritic growth - either dense branching or ramified islands - are formed at the solid-electrolyte interface. We show how the diffusion length of ions in the electrolyte influences morphology selection and how instability induced by initial surface roughness, combined with local enhancement of electric field, gives rise to non-uniform branched deposition as a result of nucleation/growth at preferred locations. Comparing the growth behavior under these different conditions provides new insight into the fundamental mechanisms of platinum nucleation.

YBa$_{2}$Cu$_{3}$O$_{7-{\delta}}$ coated conductors (CCs) have achieved high critical current densities ($\textit{J}_{c}$) that can be further increased through the introduction of additional defects using particle irradiation. However, these gains are accompanied by increases in the flux creep rate, a manifestation of competition between the different types of defects. Here, we study this competition to better understand how to design pinning landscapes that simultaneously increase $\textit{J}_{c}$ and reduce creep. CCs grown by metal organic deposition show non-monotonic changes in the temperature-dependent creep rate, $\textit{S}(\textit{T})$. Notably, in low fields, there is a conspicuous dip to low $\textit{S}$ as temperature ($\textit{T}$) increases from ~20 K to ~65 K. Oxygen-, proton-, and Au-irradiation substantially increase $\textit{S}$ in this temperature range. Focusing on an oxygen-irradiated CC, we investigate the contribution of different types of irradiation-induced defects to the flux creep rate. Specifically, we study $\textit{S}(\textit{T})$ as we tune the relative density of point defects to larger defects by annealing both an as-grown and an irradiated CC in O$_{2}$ at temperatures $\textit{T}_{A}$ = 250${\deg}$C to 600${\deg}$C. We observe a steady decrease in $\textit{S}$($\textit{T}$ > 20 K) with increasing $\textit{T}_{A}$, unveiling the role of pre-existing nanoparticle precipitates in creating the dip in $\textit{S}(\textit{T})$ and point defects and clusters in increasing $\textit{S}$ at intermediate temperatures., Comment: 22 pages, 7 figures

The optimization of nanopore-based devices is closely related to the nanopore three-dimensional (3D) structures. In this paper, faceted nanopores were fabricated in magnesium (Mg) by aligning the electron beam (e-beam) along the [0001] direction. Detailed structural characterization by transmission electron microscopy reveals the existence of two 3D structures: hexagonal prism-shaped and hourglass-shaped 3D morphologies. Moreover, the 3D structures of nanopores are also found to depend on the widest nanopore diameter-to-thickness ratio (D/t). A plausible formation mechanism for different 3D structures is discussed. Our results incorporate a critical piece of information regarding the nanopore 3D structures in Mg and may serve as an important design guidance for the size- and shape-controllable fabrication of solid-state nanopores applying the e-beam sculpting technique.

We demonstrate that 3.5-MeV oxygen irradiation can markedly enhance the in-field critical current of commercial 2nd generation superconducting tapes with an exposure time of just one second per 0.8 cm2. The speed demonstrated here is now at the level required for an industrial reel-to-reel post-processing. The irradiation is made on production line samples through the protective silver coating and does not require any modification of the growth process. From TEM imaging, we identify small clusters as the main source of increased vortex pinning., Comment: 4 figures

The atomic-scale oxide growth dynamics are directly revealed by in situ high resolution transmission electron microscopy during the oxidation of Mg surface. The oxidation process is characterized by the layer-by-layer growth of magnesium oxide (MgO) nanocrystal via the adatom process. Consistently, the nucleated MgO crystals exhibit faceted surface morphology as enclosed by {200} lattice planes. It is believed that the relatively lower surface energies of {200} lattice planes should play important roles, governing the growth mechanism. These results facilitate the understanding of the nanoscale oxide growth mechanism that will have an important impact on the development of magnesium or magnesium alloys with improved resistance to oxidation.

In this paper, using high resolution transmission electron microscopy, we showed the fabrication of faceted nanopores with various shapes in magnesium by focused electron beam (e-beam). The characteristics of nanopore shapes and the crystallographic planes corresponding to the edges of the nanopores were discussed in detail. Interestingly, by manipulating the e-beam (e.g., irradiation direction and duration), the nanopore shape and size could be effectively controlled along different directions. Our results provide important insight into the nanopore patterning in metallic materials and are of fundamental importance concerning the relevant applications, such as nanopore-based sensor, etc.

Employing electrons for direct control of nanoscale reaction is highly desirable since it provides fabrication of nanostructures with different properties at atomic resolution and with flexibility of dimension and location. Here, applying in situ transmission electron microscopy, we show the reversible oxidation and reduction kinetics in Ag, well controlled by changing the dose rate of electron beam. Aberration-corrected high-resolution transmission electron microscopy observation reveals that O atoms are preferably inserted and extracted along the {111} close-packed planes of Ag, leading to the nucleation and decomposition of nanoscale Ag2O islands on the Ag substrate. By controlling electron beam size and dose rate, we demonstrated fabrication of an array of 3 nm Ag2O nanodots in an Ag matrix. Our results open up a new pathway to manipulate atomistic reaction with electron beam towards the precise fabrication of nanostructures for device applications.