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The ordered structure of platinum-cobalt (Pt-Co) alloy nanoparticles has been studied actively because the structure influences their magnetic and catalytic properties. On the Pt-Co alloy's surface, Pt atoms preferentially segregate during annealing to reduce the surface energy. Such surface segregation has been shown to promote the formation of an ordered structure near the surface of Pt-Co thin films. Although this phenomenon seems also useful to control the nanoparticle structure, this has not been observed. Here, we have studied the ordered structure in annealed Pt@Co core-shell nanoparticles using a scanning transmission electron microscope. The nanoparticles were chemically synthesized, and their structural changes after annealing at 600 °C, 700 °C, and 800 °C for 3 h were observed. After being annealed at 600 °C and 800 °C, the particles contained the L1

All-scale scattering contributes to the reduction of lattice thermal conductivity of SiGe-based TE materials and leads to a maximum ZT value of 1.47 at 873 K, which is best one in the temperature range of 300–900 K ever reported.

Even though there has been a lot of studies on the magnetic properties of Fe x TiS2 and their corresponding atomic structures at different Fe concentrations, the dependency of the properties on the Fe atomic arrangement has not been fully clarified yet. In this study, Fe x TiS2 structures, synthesized by chemical vapor transport technique at Fe concentrations of 0.05, 0.10, 0.15, 0.20 0.25 and 0.33, were observed three-dimensionally using a transmission electron microscope and their corresponding magnetization values were measured using a superconducting quantum interference device. The results show a switch from local in-plane two-dimensional (2D) ordering of \sqrt 3 a and 2a at concentrations below 0.15 to three-dimensional (3D) ordering of 2a × 2a × 2c at x = 0.20 and 0.25, as well as \sqrt 3 a × \sqrt 3 a × 2c superstructures at x = 0.33, although it should be noted that the x = 0.20 sample only had partial ordering of Fe atoms. The type of Fe ordering present in Fe x TiS2 could be explained by the balance of cohesive energy of neighboring Fe atoms and local strain energy imposed on the host structure due to the formation of Fe clusters. It is also found that the switch from 2D to 3D Fe order coincides with the magnetic measurements, which reveal spin-glass behavior below x = 0.15 and ferromagnetic behavior above x = 0.20. This suggests that the magnetic properties of the Fe x TiS2 structure are highly influenced by the ordering of Fe atoms between planes.

High-performance PtNi alloy nanoparticle-supported multiwalled carbon nanotube composite (PtNi/MWCNT) electrocatalysts can be prepared via one-pot preparation for oxygen reduction reaction. This route of preparation utilizes the pyrolytic decomposition of metal precursors, such as Pt(acac)2 with Ni precursors, nickel bis(trifluoromethanesulfonyl)amide (Ni[Tf2N]2) or nickel acetylacetonate (Ni(acac)2), in an ionic liquid (IL), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide ([N1,1,1,3][Tf2N]). Currently, there is insufficient information concerning the effect of difference in preparation conditions on the formation mechanism and catalytic activity of PtNi/MWCNT. In this article, a staircase heating process was used to investigate the PtNi alloy nanoparticle formation mechanism and catalytic activity of the resulting PtNi/MWCNT. We found that the alloy formation process, composition, and crystal structure, which directly affect the electrocatalytic activity, strongly depended on the Ni precursor species and heating process. The catalytic performance of certain PtNi/MWCNTs collected during the staircase heating process was better than that of PtNi/MWCNTs produced via the conventional heating process.

The structure-dependent electronic properties of suspended graphene nanoribbon (GNR) have still been important issues. However, these properties have been rarely investigated experimentally due to technical difficulties to produce high-quality suspended GNRs and the identification of atomic structures. Here, we report the electronic properties of suspended GNRs by in situ transmission electron microscopy observations to simultaneously obtain the structural information while measuring the current-voltage (I-V) curves. The suspended GNRs could be obtained by convergent electron beam nanosculpting after careful cleaning by current annealing. The I-V curves were measured for GNRs with a mixture of both zigzag and armchair edges (MGNR) with widths of 3.7 to 1.9 nm and also zigzag edge GNRs (ZGNR) with widths of 1.7 to 1.2 nm. The I-V curves for the ZGNRs were different from those of the MGNRs, as follows. (1) The ZGNRs showed a sharp increase at the threshold voltage in differential conductance-voltage curves. (2) The band gaps measured for ZGNRs were smaller than the band gaps calculated using the GW approximation. (3) The threshold voltage increased with the GNR length. These findings support magnetic-insulator and nonmagnetic-metal nonequilibrium phase transitions as theoretically predicted. Narrow and short ZGNR represents the potential for further nanosized switching devices.

Pt and PtNi alloy nanoparticle-supported multiwalled carbon nanotubes (Pt/MWCNTs and PtNi/MWCNTs) are prepared by a one-pot pyrolysis method with the N,N,N-trimethyl-N-propylammonium bis(trifluorom...

The surface bond nature of face centered cubic metals has been controversial between hardening and softening theoretically because of the lack of precise measurement. Here, we precisely measured the size dependence of Young's modulus of gold [111] nanocontacts with a clean surface by our in situ TEM-frequency modulation force sensing method in ultrahigh vacuum at room temperature. Young's modulus gradually decreased from ca. 80 to 30 GPa, as the nanocontact width decreased below 2 nm, which could be explained by surface softening; Young's modulus of the outermost atomic layer was estimated to be approximately 22 GPa, while that of the other part was almost the same with the bulk.

Metal atomic chains have been reported to change their electronic or magnetic properties by slight mechanical stimulus. However, the mechanical response has been veiled because of lack of information on the bond nature. Here, we clarify the bond nature in platinum (Pt) monatomic chains by our developed in-situ transmission electron microscope method. The stiffness is measured with sub N/m precision by quartz length-extension resonator. The bond stiffnesses at the middle of the chain and at the connecting to the base are estimated to be 25 and 23 N/m, respectively, which are higher than the bulk counterpart. Interestingly, the bond length of 0.25 nm is found to be elastically stretched to 0.31 nm, corresponding to 24% in strain. Such peculiar bond nature could be explained by a novel concept of "string tension". This study is a milestone that will significantly change the way we think about atomic bonds in one-dimensional substance., 20pages, 4 figures

Even though there has been a lot of studies on the magnetic properties of Fe

Analysis of subpercent local strain is important for a deeper understanding of nanomaterials, whose properties often depend on the strain. Conventional strain analysis has been performed by measuring interatomic distances from scanning transmission electron microscopy (STEM) images. However, measuring subpercent strain remains a challenge because the peak positions in STEM images do not precisely correspond to the real atomic positions due to disturbing influences, such as random noise and image distortion. Here, we utilized an advanced datadriven analysis method, Gaussian process regression, to predict the true strain distribution by reconstructing the true atomic positions. As a result, a precision of 0.2% was achieved in strain measurement at the atomic scale. The method was applied to gold nanoparticles of different shapes to reveal the shape dependence of the strain distribution. A spherical gold nanoparticle showed a symmetric strain distribution with a contraction of similar to 1% near the surface owing to surface relaxation. By contrast, a gold nanorod, which is a cylinder terminated by hemispherical caps on both sides, showed nonuniform strain distributions with lattice expansions of similar to 0.5% along the longitudinal axis around the caps except for the contraction at the surface. Our results indicate that the strain distribution depends on the shape of the nanomaterials. The proposed data-driven analysis is a convenient and powerful tool to measure the strain distribution with high precision at the atomic scale.

Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00 l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor.

Recently, visualization of lithium ions has brought great benefit for understanding lithium movement in the cathode, electrolyte and anode materials of lithium ion battery. It has been achieved by several methods such as spherical aberration corrected scanning transmission electron microscopy, multivariable analysis, advanced electron holography and so on, which was reviewed by the special issue, 'Challenges for Lithium Detection' in Microscopy (Vol. 66, No. 1, 2017). In this paper, recent research progress in lithium detection is introduced as a follow-up for the special issue.

In this work, Zr-doped CeO2 (Ce1-xZrxO2, CZO) films with (001) preferential orientation were fabricated on biaxially textured NiW alloy substrates by using a novel sol-gel method. The precursor solutions were synthesized through a newly developed process using common inorganic metal salts of Zr and Ce as the starting materials instead of organic salts. The influence of annealing temperature and the Ce/Zr mole ratio in the precursor solutions on the growth texture of CZO films was investigated. The precursor solutions with the concentration of 0.3 mol/L were coated on the Ni5W substrates using a dip-coating method and then heat-treated at 1050 °C for an hour under a reducing atmosphere of high-purity Ar with 5 vol% H2. The CZO thin films show excellent c-axis preferential orientation when the content of Zr in CZO thin film is less than 40%. The full width of half maximum of the phi scan of (111) reflection and omega scan of (200) reflection of CZO films is as low as the value of about 5° and 6°, respectively. Moreover, it is found that the inside of CZO thin film exhibits quite dense and uniform without cracks and porosity with the aid of the scanning transmission electron microscopy analysis by which the epitaxial growth relationship of (220)CZO // (200)NiW between CZO and NiW is simultaneously confirmed. Finally, highly (00 l)-oriented YBCO film with good superconducting properties was deposited on CZO buffered NiW substrate. The above results indicate that the CZO film is a quite promising candidate of single buffer layer architecture for YBCO coated conductor.

In this work, YBCO films were epitaxially grown on Ce1−xZrxO2 (CZO) buffered yttria stabilized zirconia (YSZ) single crystal substrates through a fluorine-free sol-gel process. The influence of two different CZO buffer architectures on the microstructure and superconducting properties of YBCO films was investigated. According to XRD results in combination with (S)TEM analysis, it was confirmed that YBCO film grown on the gradient CZO buffer layer (CZO-G) exhibits better in-plane and out-of-plane texture than YBCO film deposited on the uniform CZO buffer layer (CZO-20). And besides, the superconducting performances especially the current-carrying capacity under magnetic field of the former was much higher than that of the latter, which means that the enhanced flux pinning force will be presented in YBCO film on CZO-G buffer layer. The maximum pinning force of the YBCO film grown on CZO-G buffer architecture is up to 17.67 GN/m3 @ 65 K. HR-STEM analysis shows that the stacking faults within YBCO matrix gave rise to the considerable nanoscale lattice-strains which may suppress the formation of Copper pairs and produce nanoscale non-superconducting regions served as pinning centers to significantly improve the flux pinning performance of YBCO film. Given the above, it has been implied that high-performance YBCO coated conductor can be developed by using a compositional gradient Ce1−xZrxO2 films as buffer architecture.

We report on crystallographic behaviors of inclined GaAs nanowires (NWs) self-crystallized on GaAs (001) substrate. The NWs were grown on hydrogen-silsesquioxane (HSQ) covered substrates using molecular beam epitaxy (MBE). Commonly, the epitaxial growth of GaAs " is="true"> 111 B (B-polar) NWs is prominently observed on GaAs (001); however, we yielded a remarkable number of epitaxially grown GaAs " is="true"> 111 A (A-polar) NWs in addition to the majorly obtained B-polar NWs. Such NW orientations are always accompanied by a typical inclined angle of 35° from (001) plane. NWs with another inclined angle of 74° were additionally observed and attributed to be " is="true"> 111 -oriented, not in direct epitaxial relation with the substrate. Such 74° NWs' existence is related to first-order three-dimensional (3D) lattice rotation taking place at the very beginning of the growth. It turns out that spatially 60° lattice rotation around " is="true"> 111 directions at GaAs seeds is essentially in charge of A- and B-polar 74° NWs. Transmission electron microscope observations reveal a high density of twinning in the B-polar NWs and twin-free characteristic in the A-polar NWs.

Graphene nanoribbons (GNRs) are expected in nanodevices and sensors but are degraded by contaminants that adsorb firmly on the surface during the transfer and lithography processes. Current annealing appears to be the most appropriate cleaning method, but its effects have not been quantitatively clarified. To this end, the cleaning processes of suspended monolayer GNRs were observed by in situ transmission electron microscopy. The gradual cleaning processes, which were successfully observed by improving the contact resistance at graphene-metal interface, showed that the GNRs was cleaned on the atomic scale in the current density range of 2.0–5.0 × 1012 A/m2. The corresponding temperature was estimated to be ∼ 700 K by finite element method. To be surprised, clean monolayer and bilayer GNRs withstood current densities of 5.1 × 1012 A/m2 and 1.7 × 1013 A/m2 (current-carrying capacities), respectively, which values were approximately three orders of magnitude higher than those of typical metals. The higher current-carrying capacity of bilayer GNR can be attributed to the formation of closed edges. This study shows that the electrical current is effective for cleaning GNR and boosting the current-carrying capacity.

A facile, efficient and rapid method for fabrication of silica-coated Fe2O3 magnetic nanoparticles (NPs) by a microwave (MW) irradiation method is reported. The homogeneous heating produced by the MW irradiation is the key to attaining the effective and uniform coating on Fe2O3 magnetic nanoparticles (NPs) in water-ethanol solution. HRTEM images confirmed the successful formation of uniform silica shells around the Fe2O3 NPs surface whereas FT-IR data show the structural differences between non-coated and silica-coated Fe2O3 NPs. These uniformly coated Fe2O3 NPs showed superior dispersibility than the bare Fe2O3 NPs as confirmed by the zeta potential measurements. For potential chemical sensor development, silica-coated Fe2O3 magnetic NPs were deposited onto a flat glassy carbon electrode (GCE, surface area, 0.0316 cm2) to give a sensor with a fast response against selective hydrazine in phosphate buffer phase. Hydrazine sensor also exhibits a good sensitivity with long-term stability and enhanced electrochemical performances. The calibration plot is linear (r2: 0.9911) over the 0.2 nM to 2.0 mM hydrazine concentration ranges. The sensitivity and detection limit are ∼12.658 μAmM−1cm−2 and 76.0 pM (signal-to-noise ratio, at a SNR of 3) respectively. It is also commenced a promising future sensitive sensor development using silica-coated Fe2O3 magnetic NPs by I-V method for the important applications of hazardous and carcinogenic compounds in environmental fields.

We propose a self-similar assembly to generate planar orientation of megamolecular polysaccharides on the nanometer scale and submicron scale. Evaporating the aqueous liquid crystalline (LC) solution on a planar air-LC interface induces polymer layering by self-assembly and rational action of macroscopic capillary forces between the layers. To clarify the mechanisms of nanometer- and submicron-scale layering, the polymer films are investigated by electron microscopy.

A compact electrochemical cell capped with a silicon nitride (SiN) film of 50 nm thick as an electron window was developed for a side-entry holder of a high-resolution scanning electron microscope (SEM). Electrodeposition and stripping of lead (Pb) were examined on a gold electrode formed on the SiN film, which was faced inside the cell filled with an aqueous solution of lead nitrite. The SEM images of growth and dissociation of Pb were recorded simultaneously with cyclic voltammograms, controlled with a two-terminal potentiostat. Particulate growth of Pb at the edge of a gold (Au) electrode was observed at the underpotential deposition of Pb, followed by dendrite growth of Pb at higher deposition potentials. The growth mode changed depending on the edge morphology of the Au electrode. This indicated that in-situ microscopic observation was invaluable for understanding the phenomena of electrodeposition in electrochemistry.

Atom-scaled ripple structure can be intrinsically formed because of thermal instability or induced stress in graphene or two-dimensional (2D) materials. However, it is difficult to estimate the period, amplitude, and shape of such a ripple structure. In this study, by applying the geometrical phase analysis method to atomically resolved transmission electron microscopy images, we demonstrate that the atom-scaled ripple structure of MoS2 nanosheet can be quantitatively analyzed at the subnanometer scale. Furthermore, by analyzing the observed ripple structure of the MoS2 nanosheet, we established that it is inclined by approximately 7.1° from the plane perpendicular to the incident electron beam; it had 5.5 and 0.3 nm in period and amplitude, respectively. For quantitative estimation of ripple structure, our results provide an effective method that contributes to a better understanding of 2D materials in the sub-nanometre scale.

Lithium ion batteries are encountering ever-growing demand for further increases in energy density. Li-rich layered oxides are considered a feasible solution to meet this demand because their specific capacities often surpass 200 mAh g−1 due to the additional lithium occupation in the transition metal layers. However, this lithium arrangement, in turn, triggers cation mixing with the transition metals, causing phase transitions during cycling and loss of reversible capacity. Here we report a Li-rich layered surface bearing a consistent framework with the host, in which nickel is regularly arranged between the transition metal layers. This surface structure mitigates unwanted phase transitions, improving the cycling stability. This surface modification enables a reversible capacity of 218.3 mAh g−1 at 1C (250 mA g−1) with improved cycle retention (94.1% after 100 cycles). The present surface design can be applied to various battery electrodes that suffer from structural degradations propagating from the surface., Surface modification of high-capacity lithium-rich layered oxides for improved capacity retention is an active area of battery materials research. Here authors demonstrate lithium-rich layered surfaces with a framework matching the host's, but with nickel atoms regularly arranged between layers.

Hydrated materials contain crystal water within their crystal frameworks and can exhibit extraordinary properties as a result. However, a detailed understanding of the mechanism involved in the hydration process is largely lacking, because the overall synthesis process is very difficult to monitor. Here, we elucidate how the insertion of crystal water mediates an anomalous spinel-to-Birnessite phase transition during electrochemical cycling in aqueous media. We find that, at the initial stage of the phase transition, crystal water is inserted into the interlayer space between MnO6 layers in the form of a hydronium ion (H3O+). The H3O+ insertion is chemically driven in the reverse (reducing) direction to the applied anodic (oxidizing) electric field, stabilizing the structure and recovering the charge balance following the deinsertion of Mn2+. A comparative investigation using various electrolyte solutions revealed that the H3O+ insertion competes with the insertion of other ionic charge carriers (Li+, Na+...

Graphene nanoribbon is an attractive material for nano-electronic devices, as their electrical transport performance can be controlled by their edge structures. However, in most cases, the electrical transport has been investigated only for graphene nanoribbons fabricated on a substrate, which hinders the appearance of intrinsic electrical transport due to screening effects. In this study, we developed special devices based on silicon chips for transmission electron microscopy to observe a monolayer graphene nanoribbon suspended between two gold electrodes. Moreover, with the development of an in-situ transmission electron microscopy holder, the current–voltage characteristics were achieved simultaneously with observing and modifying the structure. We found that the current–voltage characteristics differed between 1.5 nm-wide graphene nanoribbons with armchair and zigzag edge structures. The energy gap of the zigzag edge was more than two-fold larger than that of the armchair edge and exhibited an abrupt jump above a critical bias voltage in the differential conductance curve. Thus, our in-situ transmission electron microscopy method is promising for elucidating the structural dependence of electrical conduction in two-dimensional materials.

The various physical properties of titanium disulfide (TiS2) crystals with intercalated iron (Fe) are reported to be influenced by the distribution of Fe atoms in the van der Waals gap between TiS2...

An in situ transmission electron microscopy (TEM) holder equipped with a quartz length-extension resonator (LER) as a force sensor was developed to examine the elastic properties of atomic-scale materials. This holder is a useful means of studying the effects of size and crystal orientation on the properties of nanomaterials via measurements of mechanical responses while simultaneously observing atomic structures. The spring constants of nanocontacts (NCs) were determined based on shifts in the resonance frequency of the LER during TEM observations. The LER spring constant and sensitivity (the ratio of the LER induced charge to its oscillation amplitude), both of which are crucial to mechanical evaluation of NCs, were precisely calibrated from an analysis of TEM images along with the output of the electronics attached to the holder. The mechanical stability of the newly developed TEM holder was sufficient to allow chains of Pt atoms in the NC to be maintained for at least several seconds. The minimum measurable NC spring constant was on the order of 1 N m-1, comparable to that associated with a single atomic bond. The spring constant of a NC composed of a single-bonded chain of two Pt atoms was found to be 13.2 N m-1. This holder therefore has significant potential with regard to the characterization of nanoscale mechanical properties.

Li 2 RuO 3 (001) films with a lithium-rich layered rocksalt structure are epitaxially grown on a Al 2 O 3 (0001) substrate through pulsed laser deposition, followed by stacking of an amorphous Li 3 PO 4 solid electrolyte. A half solid-state battery with a Li 3 PO 4 /Li 2 RuO 3 cathode, liquid electrolyte, and lithium anode exhibits two redox peak pairs at 3.4 and 3.6 V, demonstrating lithium intercalation in the Li 2 RuO 3 through the Li 3 PO 4 solid electrolyte. All-solid-state batteries are fabricated by Li or In metal anode deposition on the Li 3 PO 4 /Li 2 RuO 3 . The Li/Li 3 PO 4 /Li 2 RuO 3 cell delivers an initial discharge capacity of 101 mAh g −1 , which does not fade significantly over 30 cycles. Furthermore, the Li 2 RuO 3 rate capability is comparable to that of a liquid-type battery. Lithium-rich layered materials are available for use as cathodes in all-solid-state batteries.

A practical procedure for retrieving quantitative phase distribution at the interface between a thin amorphous germanium (a-Ge) film and vacuum based on the transport of intensity equation is proposed. First, small regions were selected in transmission electron microscopy (TEM) images with three different focus settings in order to avoid phase modulation due to low frequency noise. Second, the selected TEM image and its three reflected images were combined for mirror-symmetry to meet the boundary requirements. However, in this symmetrization, extra phase modulation arose due to the discontinuous nature of Fresnel fringes at the boundaries among the four parts of the combined image. Third, a corrected phase map was obtained by subtracting a linear fit to the extra phase modulation. The phase shift for a thin a-Ge film was determined to be approximately 0.5 rad, indicating that the average inner potential was 18.3 V. The validity of the present phase retrieval is discussed using simple simulations.

By exploiting characteristics such as negligible vapour pressure and ion-conductive nature of an ionic liquid (IL), we established an in situ scanning electron microscope (SEM) method to observe the electrode reaction in the IL-based Li-ion secondary battery (LIB). When 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([C2mim][FSA]) with lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) was used as the electrolyte, the Si negative electrode exhibited a clear morphology change during the charge process, without any solid electrolyte interphase (SEI) layer formation, while in the discharge process, the appearance was slightly changed, suggesting that a morphology change is irreversible in the charge-discharge process. On the other hand, the use of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mim][TFSA]) with Li[TFSA] did not induce a change in the Si negative electrode. It is interesting to note this distinct contrast, which could be attributed to SEI layer formation from the electrochemical breakdown of [C2mim](+) at the Si negative electrode|separator interface in the [C2mim][TFSA]-based LIB. This in situ SEM observation technique could reveal the effect of the IL species electron-microscopically on the Si negative electrode reaction.

Electrochemical transmission electron microscopy (ECTEM) is one of in-situ TEM observation methods. It enables us to visualize local structure and/or composition change at the interface between a solid electrode and a liquid electrolyte during the electrochemical process.

Density functional theory calculations are carried out to investigate the atomic and electronic structures of the $4H\text{-SiC}(0001)/{\mathrm{SiO}}_{2}$ interface. We find two characteristic interface atomic structures in scanning transmission electron microscopy images: One is an interface in which the density of atoms at the first interfacial SiC bilayer is greater than that in the SiC substrate, while the other is an interface where the density of atoms at the first interfacial SiC bilayer is lower. Density functional theory calculations reveal that the difference in the scanning transmission electron microscopy images is a reflection of the atomic structures of these two interfaces. In addition, it has been reported that the floating states, which appear at the conduction band edge of a $4H\text{-SiC}(0001)/{\mathrm{SiO}}_{2}$ interface, affect the electronic structure of the interface and cause marked scattering of the electrons flowing along the interface [S. Iwase, C. J. Kirkham, and T. Ono, Phys. Rev. B 95, 041302(R) (2017)]. Interestingly, we find that the floating states do not appear at the conduction band edge of one of the two interfaces. These results provide physical insights into understanding and controlling the electronic structure and carrier mobility of electronic devices using wide-band-gap semiconductors.

Gold (Au) nanocontacts (NCs) being stretched in the [110] direction were analyzed using a transmission electron microscopy (TEM) holder equipped with a force sensor to measure spring constants. The Au NCs showed similar change in spring constant with electrical conductance, regardless of the initial shape of NC formed during stretching of contacted two Au wires. The Young's modulus of the Au NC was estimated to be close to the bulk value. This study demonstrated the performance of TEM-combined method to characterize the mechanical properties of nanomaterials via knowing their shape and size.

Fast charge-discharge process has been reported to give a high capacity loss. A nanobattery consisting of a single LiMn2O4 nanowire cathode, ionic liquid electrolyte and lithium titanium oxide anode was developed for in situ transmission electron microscopy. When it was fully charged or discharged within a range of 4 V in less than half an hour (corresponding average C rate: 2.5C), Li-rich and Li-poor phases were observed to be separated by a transition region, and coexisted during whole process. The phase transition region moved reversibly along the nanowire axis which corresponds to the [011] direction, allowing the volume fraction of both phases to change. In the electron diffraction patterns, the Li-rich phase was seen to have the (100) orientation with respect to the incident electron beam, while the Li-poor phase had the (111̅) orientation. The orientation was changed as the transition region moved. However, the nanowire did not fracture. This suggests that a LiMn2O4 nanowire has the advantage of preventing capacity fading at high charge rates.

Recent advances in in situ transmission electron microscopy (TEM) techniques have provided unprecedented knowledge of chemical reactions from a microscopic viewpoint. To introduce volatile liquids, in which chemical reactions take place, use of sophisticated tailor-made fluid cells is a usual method. Herein, a very simple method is presented, which takes advantage of nonvolatile ionic liquids without any fluid cell. This method is successfully employed to investigate the essential steps in the generation of gold nanoparticles as well as the growth kinetics of individual particles. The ionic liquids that we select do not exhibit any anomalous effects on the reaction process as compared with recent in situ TEM studies using conventional solvents. Thus, obtained TEM movies largely support not only classical theory of nanoparticle generation but also some nonconventional phenomena that have been expected recently by some researchers. More noteworthy is the clear observation of lattice fringes by high-resolution TEM even in the ionic liquid media, providing intriguing information correlating coalescence with crystal states. The relaxation of nanoparticle shape and crystal structure after the coalescence is investigated in detail. The effect of crystal orientation upon coalescence is also analyzed and discussed.

The A V{sub 2}O{sub 4} (A=Mg{sup 2+}, Zn{sup 2+}, Cd{sup 2+}) spinels are three-dimensional spin-1 frustrated systems with orbital degree of freedom, which have been known to possess intriguing orbital states causing releases of spin frustration at low temperatures. We have performed synchrotron X-ray and convergent beam electron diffraction measurements for one of these vanadates, MgV{sub 2}O{sub 4} in order to clarify its crystal structure in the high temperature cubic phase, which is regarded as an important starting point for understanding the details of the low temperature phase. We have successfully observed that the [001] zone axis convergent beam electron diffraction pattern exhibits 4mm symmetry, suggesting the space group of Fd3{sup ¯}m in the cubic MgV{sub 2}O{sub 4}. It has also been demonstrated that the crystal structure of the cubic MgV{sub 2}O{sub 4} contains VO{sub 6} octahedra elongated along the threefold rotation axis. Based on our results, we discuss the orbital states of MgV{sub 2}O{sub 4} as well as the other spinel vanadates. - Graphical abstract: Precise geometry of the VO{sub 6} octahedra in the cubic phase of MgV{sub 2}O{sub 4} spinel determined with the synchrotron powder XRD data. - Highlights: • We examined the crystal structure of the cubicmore » phase of MgV{sub 2}O{sub 4} spinel. • We prepared the single crystal and powdered sample of MgV{sub 2}O{sub 4} with high quality. • The result of the CBED measurement agrees with the space group of Fd3{sup ¯}m in the phase. • The cubic phase has VO{sub 6} octahedra elongated along the threefold rotation axis.« less

A through-focus series of annular bright field (ABF) images were observed simultaneously with high-angle annular dark field (HAADF) images of very thin lithium manganese oxide (LiMn 2 O 4 ), a typical cathode material used in lithium ion batteries, using a spherical aberration corrected electron microscope with a 50 pm resolution (R005). The ABF images showed dark dips at the positions of Li and Mn–O atomic columns, which reversed to bright peaks when the defocus sign was changed, as commonly observed in phase contrast images. The optimal defocus for the ABF images was about 2 nm of over-focus, while that for the HAADF images was 2 nm of under-focus for an incident probe with a convergent semi-angle of 30 mrad. These experimental results are interpreted based on a weak-phase-object approximation.