The authors report a study of molecular beam deposition of MgO films on amorphous SiO2 and (0001) GaN surfaces over a large range of temperatures (25–400 °C) and molecular oxygen growth pressures (10−7–10−4 Torr). This study provides insight into the growth behavior of an oxide with volatile metal constituents. Unlike other materials containing volatile constituents (e.g., GaAs, PbTiO3), all components of MgO become volatile at normal epitaxial growth temperatures (≥250 °C). Consequently, defining which species is the adsorption controller becomes ambiguous. Different growth regimes are delineated by the critical substrate temperature for Mg re-evaporation and the Mg:O flux ratio. These regimes have impact on phase purity, quartz crystal microbalance calibration, and film microstructure. The universal decay in deposition rate above growth 10−5 Torr O2 is also considered. By introducing a third flux of inert argon gas, rate reduction is attributed to increased molecular scattering and not oxidation of the metal source.

Several binary intermetallic compounds—each containing a rare-earth (RE) element paired with a transition metal (TM)—were prepared by self-propagating, high-temperature synthesis (SHS). Thin multilayers, composed of alternating Sc or Y (RE element) and Ag, Cu, or Au (TM), were first deposited by direct current magnetron sputtering. Once the initially distinct layers were stimulated and caused to mix, exothermic reactions propagated to completion. X-ray diffraction revealed that Sc/Au, Sc/Cu, Y/Au, and Y/Cu multilayers react in vacuum to form single-phase, cubic B2 structures. Multilayers containing Ag and a RE metal formed cubic B2 (RE)Ag and a minority (RE)Ag2 phase. The influence of an oxygen-containing environment on the reaction dynamics and the formation of phase were investigated, providing evidence for the participation of secondary combustion reactions during metal-metal SHS. High-speed photography demonstrated reaction propagation speeds that ranged from 0.1–40.0 m/s (dependent on material system and foil design). Both steady and spin-like reaction modes were observed.

The cooperative self-assembly of organic–inorganic siliceous composite structures has been studied from the aspect of inorganic precursors. We reveal that the vesicular or mesostructured materials can be obtained selectively by just changing the silica sources in one templating system. For poly(ethylene oxide)-type block copolymers with either poly(propylene oxide) or poly(butylene oxide) as the hydrophobic moieties, when the other synthesis parameters are exactly the same, the use of tetramethyl orthosilicate (TMOS) as a silica source gives rise to highly ordered mesostructures, while the use of tetraethyl orthosilicate (TEOS) leads to vesicles or foams. The attenuated total reflection Fourier transform infrared (ATR-FTIR) technique is used to monitor the silicate species derived from the hydrolysis and condensation of TMOS and TEOS as a function of the reaction time. On the basis of the ATR-FTIR results, we propose a “differentiating effect” at relatively high pH (4.7) to interpret the influence of different silica sources on the self-organized composite structures. For comparison, a “leveling effect” at relatively low pH (strong acidic conditions) is revealed to explain that both TMOS and TEOS lead to the same mesostructures. Our contribution provides a feasible and designable method to synthesize from conventional ordered mesostructures to novel vesicular structures, which are significant for their future practical applications.

Graphene, a single atom–thick plane of carbon atoms arranged in a honeycomb lattice, has captivated the attention of physicists, materials scientists, and engineers alike over the five years following its experimental isolation. Graphene is a fundamentally new type of electronic material whose electrons are strictly confined to a two-dimensional plane and exhibit properties akin to those of ultrarelativistic particles. Graphene's two-dimensional form suggests compatibility with conventional wafer processing technology. Extraordinary physical properties, including exceedingly high charge carrier mobility, current-carrying capacity, mechanical strength, and thermal conductivity, make it an enticing candidate for new electronic technologies both within and beyond complementary metal oxide semiconductors (CMOS). Immediate graphene applications include high-speed analog electronics and highly conductive, flexible, transparent thin films for displays and optoelectronics. Currently, much graphene research is focused on generating and tuning a bandgap and on novel device structures that exploit graphene's extraordinary electrical, optical, and mechanical properties.

For more than two decades, scientists and engineers have focused on impending limitations (from high-power densities and heat distribution to device patterning) that constrain the future miniaturization of conventional silicon technology. Thus far, academic and industrial efforts have risen to the challenge and continue to advance planar silicon processing, pushing traditional microtechnology to the nanometer scale. However, insurmountable limitations, both of physical nature and cost, still loom and motivate the research of new nanomaterials and technologies that have the potential to replace and/or enhance conventional silicon systems. As time has progressed, another Group IV element has emerged as a front-runner, looking beyond silicon, in the form of carbon-based nanotechnology. The focus of this issue is to provide a comprehensive look at the state-of-the-art in carbon-based nanomaterials and nanotechnologies and their potential impact on conventional silicon technologies, which are not limited to electronics but also encompass micro- and nanoelectromechanical systems, optoelectronics, and memory. Recent advances in carbon nanotube growth, sorting, and optoelectronics will be discussed, and the relatively new and surging area of graphene research will be introduced. In addition, progress in controlling the growth and properties of ultrananocrystalline and nanocrystalline diamond thin films will be reviewed. These efforts are multidisciplinary, heavily materials focused, and tend to translate information and ideas to other carbon-based studies (e.g., graphene is the building block of carbon nanotubes).

4H-silicon carbide (SiC) wafers were annealed at 1300 and 1600 °C for 30 min and 60 min in a conventional and purified Ar atmosphere. The surface roughness before and after annealing was evaluated by atomic force microscopy. The surface roughness before annealing was approximately 2.37 nm in root mean square. The roughness, after annealing for 30 min at 1300 and 1600 °C in a conventional Ar furnace, was increased to 4.53 and 14.9 nm, respectively. The roughness, after annealing for 60 min, was 5.01 and 19.1 nm, respectively. In this study, the G3 grade Ar gas (99.999%) was supplied in the conventional furnace tube. When the Ar gas was purified to an impurity concentration of less than 1 ppb, and it was supplied in the leak-tight furnace tube, the roughness after 30-min annealing improved 4.27 and 6.93 nm at 1300 and 1600 °C, respectively. The roughness after 60-min annealing was also reduced to 3.54 and 9.28 nm, respectively. We assume that a significant reduction of H2O concentration in the annealing atmosphere might play an important role in suppressing surface roughening of SiC during high-temperature annealing.

Precipitation of ZrCu with the B2 structure in Zr50Cu50–xAlx (x = 0, 4, 6) metallic glasses by rapidly heating and cooling was investigated. By rapidly heating and cooling, the ZrCu B2 phase precipitates the most in Zr50Cu46Al4 metallic glass plates prepared by tilt-casting without using a silica nozzle. The amount of the ZrCu B2 phase precipitated in Zr50Cu46Al4 metallic glass ribbons prepared by using a silica nozzle decreases by Si diffused from the silica nozzle during the preparation. This work is discussed from the viewpoint of crystallization behavior and why larger Zr-based bulk metallic glasses can be formed by suction, tilt, and cap casting without using a silica nozzle.

Phase-pure nanostructured WB ceramics are hot pressed at ultrahigh pressures of 1.0 to 3.0 GPa and high temperatures of 700 to 1000 °C (UHPHT) for 60 min. The UHPHT samples are nanograin size from 15 to 40 nm. Our experimental observation shows that ultrahigh pressure could improve densification, and the density of WB samples could reach 99.4% of theoretical. The comparative experiments carried out at ambient pressure and temperatures of 550 to 1100 °C for 60 min indicate that the external pressure was favorable for phase-pure and highly dense WB formation. In addition, the UHPHT samples give a high hardness value of 28.9 ± 0.8 GPa.

This paper presents experimental and theoretical studies of the adhesion between the drug-eluting layer and a Parylene C primer layer in coatings present on a model drug-eluting stent. To quantify adhesion, Brazil nut sandwich specimens were prepared mimicking the layers of this coating. These samples were stressed to fracture, and the resulting initial cracks at the Parylene C/drug interface were used to measure the dependence of interfacial fracture energy of mode mixity. The mating fracture surfaces were then analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The interfacial energy release rates were obtained over a wide variety of mode mixities. Adhesion and fracture mechanics models were then used to estimate the mode mixity dependency of interfacial fracture toughness. Fracture toughness was found to be larger under higher mode mixity than that under lower mixity and the analytical model showed close agreement with experimental results.