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The development of ultrathin barrier films is vital to the advanced semiconductor industry. Graphene appears to hold promise as a protective coating; however, the polycrystalline and defective nature of engineered graphene hinders its practical applications. Here, we investigate the oxidation behavior of graphene-coated Cu foils at intrinsic graphene defects of different origins. Macro-scale information regarding the spatial distribution and oxidation resistance of various graphene defects is readily obtained using optical and electron microscopies after the hot-plate annealing. The controlled oxidation experiments reveal that the degree of structural deficiency is strongly dependent on the origins of the structural defects, the crystallographic orientations of the underlying Cu grains, the growth conditions of graphene, and the kinetics of the graphene growth. The obtained experimental and theoretical results show that oxygen radicals, decomposed from water molecules in ambient air, are effectively inverted at Stone–Wales defects into the graphene/Cu interface with the assistance of facilitators. [ABSTRACT FROM AUTHOR]

The enhanced high-temperature creep resistance in alumina/single-wall carbon nanotubes (SWNTs) composites has been attributed to the unprecedented grain-boundary structure of these composites, where the SWNTs bundles segregated at the alumina grain boundaries partially impede grain-boundary sliding. In this study, the effect of SWNTs distributions at alumina grain boundaries on the creep behavior of alumina/SWNTs composites has been investigated. Microstructures of two different alumina/10 vol% SWNTs composites, one with heterogeneous and the other with homogenous distributions of SWNTs at grain boundaries, have been characterized quantitatively. The steady-state creep rate (uniaxial compression) in the heterogeneous composite has been found to be over three times higher than that in the homogeneous composite at 1300° and 1350°C (argon atmosphere). It is argued that the less uniform distribution of SWNTs at the alumina grain boundaries in the heterogeneous composite results in less effective obstruction of grain-boundary sliding, and attendant higher creep rate. This also results in more efficient recovery in that composite. [ABSTRACT FROM AUTHOR]

The tensile fractures of ultrafine-grained (UFG) Al-Mg alloy with a bimodal grain size were investigated at the micro- and macroscale using transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with focused ion beam (FIB), and optical microscopy. The nanoscale voids and crack behaviors near the tensile fracture surfaces were revealed in various scale ranges and provided the evidence to determine the underlying tensile deformation and fracture mechanisms associated with the bulk bimodal metals. The bimodal grain structures exhibit unusual deformation and fracture mechanisms similar to ductile-phase toughening of brittle materials. The ductile coarse grains in the UFG matrix effectively impede propagation of microcracks, resulting in enhanced ductility and toughness while retaining high strength. In view of the observations collected, we propose a descriptive model for tensile deformation and fracture of bimodal UFG metals. [ABSTRACT FROM AUTHOR]

Cryomilling was successfully employed to fabricate particulate B4C-reinforced Al matrix nanocomposite powders. In order to investigate the microstructural evolution during cryomilling, composite powders were milled for different times. These powders were collected from the milling chamber and the microstructures were characterized to reveal the formation mechanism for this nanocomposite. The microstructural evolution, including the morphology and size of the milled composite powders. the size and distribution of the B4C, and the dimension of the A1 grains, is discussed on the basis of the experimental results. [ABSTRACT FROM AUTHOR]

We report that the substrate-free gas-phase graphene synthesis method produces clean and highly ordered graphene sheets that are similar in quality to the graphene obtained through the mechanical exfoliation of highly oriented pyrolytic graphite. [ABSTRACT FROM AUTHOR]

Quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated on Si wafers by embedding core-shell CdSe/ZnS nanocrystals in TiO2 thin films via plasma-enhanced metallorganic chemical vapor deposition. The n-TiO2/QDs/p-Si LED devices show typical p-n diode current-voltage and efficient electroluminescence characteristics, which are critically affected by the removal of QD surface ligands. The TiO2/QDs/Si system we presented can offer promising Si-based optoelectronic and electronic device applications utilizing numerous nanocrystals synthesized by colloidal solution chemistry. [ABSTRACT FROM AUTHOR]

Ti1-xCoxO2-δ nanobelts were synthesized without using any metal catalysts by metallorganic chemical vapor deposition. The nanobelts consisted of ∼10–20 nm nanocrystallites, which were dominantly rutile structure. The Ti0.986Co0.014O2-δ nanobelt sample showed a magnetic anisotropy with a high coercive field value (∼500 Oe) at room temperature, significantly affected by intrinsic effect. In contrast, the Ti0.982Co0.018O2-δ nanobelt sample revealed isotropic magnetic characteristics due to enhanced Co clustering. A few or several Co clusters per nanobelt were typically observed even in the lightly Co-doped Ti0.986Co0.014O2-δ nanobelts because of the very thin thickness (∼20 nm) and high specific surface area of nanobelts. [ABSTRACT FROM AUTHOR]

With the acceleration of the scaling down of integrated circuits, it has become very challenging to fabricate a metal–insulator–metal (MIM) capacitor with a high capacitance density and low leakage current for nanoscale dynamic random access memory. Yttria-stabilized-zirconia (YSZ) thin films, one of the insulators in the constitution of MIM capacitors, have been reported to have various crystal structures from the monoclinic phase to the cubic phase according to different Y doping levels. The electrical characteristics depend on the crystal structure of the YSZ thin film. Here, we report the local crystallization of YSZ thin films via Joule heating and the leakage current induced during in situ transmission electron microscopy biasing tests. We studied the crystallization process and the increase in the leakage current using experimental and simulation results. It is important to understand the relationship between the crystallinity and electrical properties of YSZ thin films in MIM capacitors. [ABSTRACT FROM AUTHOR]

The effective synthesis of atomically thin molybdenum disulfides (MoS2) of high quality and uniformity over a large area is essential for their use in electronic and optical devices. In this work, we synthesize MoS2 that exhibit a high quality and large area uniformity using chemical vapor deposition (CVD) with volatile S organic compound and NaCl catalysts. In the latter process, the NaCl enhances the growth rate (5 min for synthesis of monolayer MoS2) and purity of the synthesized MoS2. The optical microscopy, Raman spectroscopy, x-ray photoemission spectroscopy, photoluminescence, and transmission electron microscopy measurements indicate that the NaCl-CVD MoS2 has a large grain size, clear Raman shift, strong photoluminescence, good stoichiometry, and 6-fold coordination symmetry. Moreover, we demonstrate that the electron mobility (10.4 cm2 V−1 s−1) and on/off current ratio (3 × 107) of monolayer MoS2 measured using a field-effect transistor are comparable to those of previously reported MoS2 synthesized using CVD. [ABSTRACT FROM AUTHOR]