In Situ Transmission Electron Microscopy for Electronics

Electronic devices are strongly influenced by their microstructures. In situ transmission electron microscopy (in situ TEM) with capability to measure electrical properties is an effective method to dynamically correlate electric properties with microstructures. We have developed tools and in situ TEM experimental procedures for measuring electronic devices, including TEM sample holders and sample preparation methods. The method was used to study metallic nanowire by electromigration, magnetoresistance of a ferromagnetic device, conductance quantization of a metallic nanowire, single electron tunnelling, and operation details of resistive random access memories (ReRAM)

Synthesis of surfactant-free Cu–Pt dendritic heterostructures with highly electrocatalytic performance for methanol oxidation reaction

A facile and free surfactant strategy is explored to synthesize Cu–Pt bimetallic nano-heterostructures with dendritic exterior. For comparison, the Cu–Pt coral-like nanoparticles are fabricated by using CTAC as a surfactant. The well-designed Cu–Pt dendritic spherical heterostructures exhibit superior enhanced electrocatalytic activity and stability toward methanol oxidation reaction in alkaline media, compared to the Cu–Pt coral-like nanoparticles and the commercial Pt/C, respectively. The advanced technique for fabricating Cu–Pt dendritic spherical heterostructures could pave a way to pursue low-cost Pt-based catalysts, maintaining highly promoted electrocatalytic performance and durability

An investigation of surface contamination introduced during He plus implantation and subsequent effects on the thermal oxidation of Cu

Ion implantation is a potential means of increasing the oxidation resistance of Cu. However, carbonaceous contamination can also be introduced onto the metal surface during this process as a consequence of pump oil within the vacuum system. This can complicate analysis of the effect of ion implantation on Cu oxidation. The present study examined the surface contamination introduced during He+ implantation. Carbonaceous contamination was indeed identified on the Cu surface and had an obvious passivation effect on Cu oxidation at 200 °C. This was ascribed to the implantation of C into the Cu to a depth of several nanometers in conjunction with He+ implantation. The Cu was protected from oxidation by the formation of a layer consisting of C, Cu and a small amount of Cu2O that inhibited the inward diffusion of oxygen

Morphological investigations of disaccharide molecules for growth inhibition of ice crystals

Freezing of solutions including disaccharides (trehalose, sucrose, and maltose) has been investigated by microscopic observations of freeze-fractured replicas using FE-TEM. Three typical features were observed: the smooth surface considered as the ice crystal, fine particles as the precipitated disaccharide molecules, and remaining part as the glass state of the solution. The expanded observations of fine-particle and its distribution investigations suggested that it was larger than 10 nm in size and averaged approximately 20-30 nm in diameter. The smallest particle was estimated to include several hundred disaccharide molecules. Based on systematic observations of trehalose solutions regarding concentrations and freezing rates, we concluded that ice crystal growth was inhibited by trehalose molecules. Since the ice crystal size reduced exponentially with increase in trehalose concentration, we could control ice crystal size formed in the frozen material. The growth inhibition of ice crystals with trehalose resulted both from a reduction in the free water in the solution due to a significant hydration effect and from an enhancement of nucleation of the ice crystals. It was confirmed that trehalose was more effective than the other disaccharide solutions examined for inhibiting the growth of ice crystals

Heterodimeric particle assemblies: Preparation of anisotropically connected spherical silica particles via surface-bound gold nanoparticles

Assemblies of heterodimeric particles were prepared through selective coupling of two kinds of spherical silica particles of different sizes by connection with gold nanoparticles attached anisotropically to the particles

Anisotropic defect distribution in He+-irradiated 4H-SiC: Effect of stress on defect distribution

Irradiation-induced anisotropic swelling in hexagonal alpha-SiC is known to degrade the mechanical properties of SiC; however, the associated physical mechanism and microstructural process remain insufficiently understood. In this study, an anisotropic swelling condition where the surface normal direction was allowed to freely expand with constraint in the lateral direction was introduced in 4H-SiC using selected-area He+ irradiation, and the internal defect distribution was investigated using transmission electron microscopy (TEM) and advanced scanning TEM. The defect distribution was compared to that in non-selected-area He+-irradiated 4H-SiC and electron-irradiated TEM-foil 4H-SiC. An anisotropic defect distribution was observed in the selected-area He+-ion-irradiated 4H-SiC, with interstitial defects preferentially redistributed in the surface normal direction ([0 004]) and negative volume defects (such as vacancies and/or carbon antisite defects) dominantly located in the lateral directions ([11 (2) over bar0] and [10 (1) over bar0]). This anisotropy of the defect distribution was substantially lower in the non-selected-area He+-irradiated and electron-irradiated samples. The stress condition in the three samples was also measured and analyzed. In the selected-area He+-irradiated 4H-SiC, compressive stress was introduced in the lateral directions (([10 (1) over bar0] and [11 (2) over bar0])), with little stress introduced in the surface normal direction ([0 004]); this stress condition was introduced at the beginning of ion irradiation. The compressive stress likely inhibits the formation of interstitial defects in the lateral directions, enhancing the anisotropy of the defect distribution in SiC

Electron energy-loss spectroscopic evaluation of depth-dependent swelling of He+ ion-irradiated 4H-SiC correlated with defect type

Various defects and amorphous transitions are the primary mechanism behind the accumulation of swelling in silicon carbide (SiC). In this study, selected-area He+ ion irradiation was carried out on single-crystal 4H-SiC using fluences of 1x10(15), 5x10(16), and 1x10(17)cm(-2) at room temperature. The defect distribution in the samples with varying irradiation fluences was analyzed using transmission electron microscopy (TEM), while the local swelling of regions under varying damage conditions was estimated using electron energy-loss spectroscopy. The results provide the range of swelling in SiC possessing different primary defect types, such as point defects or tiny clusters, black spot defects, and amorphous SiC. A saturation swelling with a value of 2%-3% in the near-surface region, induced by point defects or tiny clusters (invisible in TEM), was observed at room temperature over the fluence range of 1x10(15) to 1x10(17)cm(-2). This saturation has already reached at a great low dose of about 0.02dpa. The swelling of the region containing black spot defects ranges from about 3% to 7%. Helium bubbles increase the volume swelling of SiC, while the He+ ion irradiation may also perform a decreasing effect on the volume swelling below a certain irradiation fluence

Non-destructive evaluation of the strain distribution in selected-area He+ ion irradiated 4H-SiC

Residual strain in silicon carbide (SiC) greatly affects its physical and chemical properties and thus the performance of SiC-based devices. Herein, the detailed strain distribution in selected-area He+ ion-irradiated 4H-SiC was evaluated using the non-destructive techniques of electron backscattering diffraction and confocal Raman microscopy (CRM). In addition to the strain introduced in the irradiated area, excessive strain induced by irradiation-induced swelling also extended into the surrounding substrate. Furthermore, great compressive strain was concentrated around the interface between the irradiated and unirradiated areas. In the strain-introduced substrate, an A(1)(LO)/A(1)(LOPC) peak variation was detected by CRM, suggesting a variation of the carrier density