Carbon nitride powder with an atomic N/C ratio of 1 has been prepared by reaction of cyanuric chloride with sodium metal. X-ray diffraction, Fourier transform infrared spectra, and x-ray photoelectron spectroscopic data provide substantial evidence for a graphite-like sp2-bonded structure composed of building blocks of s-triazine rings bridged by carbon-carbon atoms in the bulk carbon nitride. The electron-microscopy results reveal that the material is spherical particles with an average diameter of 50 nm. The optical properties and thermal stability are also characterized. Based on the experimental results, it is deduced that the structure of as-prepared material carbon nitride has polyether structure.

Isothermal sections in the Ni–Al–Ga–N quaternary phase diagram were calculated to provide a greater understanding of interfacial reactions between Ni contacts and AlxGa1−xN. The calculations were performed employing a thermodynamic database of the Ni–Al–Ga–N system that was constructed by combining the six binary systems of the four component system. The model of the Ga–N binary system was created in this work. The models of the Ni–Ga and Ni–Al systems, both of which were taken from the literature, were modified to be compatible with one another. Thermodynamic data and phase boundaries for other binary systems were taken from the literature, as was information on portions of the Al–Ga–N and Ni–Al–Ga phase diagrams. The calculated sections reveal that during reaction between Ni and AlxGa1−xN, Ni is favored to react with the GaN component of the semiconductor alloy, leaving an Al-enriched AlxGa1−xN. These predictions are consistent with a recent analysis of the Ni, Al, and Ga elemental distributions across the interface between a Ni thin film and an Al0.47Ga0.53N epitaxial layer following annealing at 850 °C. Consideration of the thermodynamic driving forces suggests that this may be a general phenomenon existing in other metal–Al–Ga–N systems.

The fundamentally changing nature of fracture in brittle coatings on compliant substrates with diminishing coating thickness is examined. Attention is focused on cracking induced by concentrated loading with a spherical indenter at the top surface. It is shown that the fracture mode undergoes transitions, from top-surface ring cracking around the contact (“thick-coating” region) to bottom-surface radial cracking at the lower ceramic surface (“intermediate” region) and, finally, back to surface ring cracking (“thin-coating” region). These transitions reflect a progressively changing stress field in the layer structures and highlight the differences in failure mechanism that may be anticipated at the large- and small-scale levels. Simple fracture relations are derived for each mode, expressing critical loads in terms of coating thickness relative to contact or sphere radius, coating strength and coating/substrate modulus mismatch. Data from finite element simulations and contact experiments on model ceramic/polymer bilayer systems are used to validate the basic elements of the analytical relations and to quantify deviations. Implications of the transitional behavior in relation to the strength of brittle coating/film systems are discussed.

A novel approach in determining the transition temperatures of NiTi shape memory alloys was investigated and compared with conventional techniques. The technique is based on microthemal analysis using a scanning thermal microscope (SThM). In particular, this method has the potential to allow the transformation temperatures of thin films to be investigated in situ. Thin film shape memory alloys have potential applications, such as microactuators, where conventional analysis techniques are either not directly applicable to such samples or are difficult to perform.

Sol-gel derived catalyst systems of cobalt, nickel, and iron were used in the growth of gallium nitride (GaN) nanowires by thermal chemical vapor deposition. A diffusion barrier matrix of titania (TiO2) has been used in which the catalysts were dispersed to have control of the catalyst particle sizes and hence on the size and morphology of the GaN nanowires. This single-step and cost-effective processing of the catalyst bed produced good-quality GaN naowires with comparable structural and optical properties with those previously reported. In a particular case, a stress-induced cubic admixture to the otherwise hexagonal structural symmetry was observed. The samples were characterized by high-resolution scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and cathodo-luminescence studies.

As the scaling of complementary metal-oxide-semiconductor (CMOS) transistors proceeds, the thickness of the SiO2 gate dielectrics shrinks rapidly and results in higher gate leakage currents. High k dielectric materials are acknowledged to be the possible solutions to this challenge, as their higher k values (e.g., 15–50) raise the physical thickness of the dielectrics that provide similar equivalent thickness of a thinner SiO2 film. In order for the high k materials to be applicable in CMOS devices, there should exist deposition technologies that can deposit highly uniform films over Si wafers with diameters as large as 200 mm. This report discusses the deposition process and the correlation between the growth conditions, structural and dielectric properties of HfO2, which is one of the most promising high k dielectric materials. Judging from the thickness uniformity, surface roughness, k value, and interfacial density of state of the HfO2 films, the metalorganic chemical vapor deposition technique was identified to be suitable for growing HfO2 films targeted at applications as CMOS gate dielectrics.

The nanotopography of the surface of silicon wafers has become an important issue in ULSI device manufacturing, as it affects the post–chemical mechanical polishing (post-CMP) uniformity of the thickness deviation of dielectric films. A spectral method is proposed to examine quantitatively how the nanotopography impacts the film thickness deviation during CMP. The nanotopography impact was investigated in terms of its dependence on the characteristics of consumables, such as the polishing pad hardness and the wafer manufacturing method. In addition, the effects of the surfactant and the abrasive size in ceria slurry on nanotopography impact were investigated. It was found that the magnitude of the post-CMP oxide thickness deviation due to nanotopography increased with the surfactant concentration in the case of smaller abrasives but was almost independent of the concentration in the case of larger abrasives. These results demonstrate that the nanotopography impact can be controlled by manipulating the slurry characteristics.

A comparative study on the effects of the substrate on the determination of hardness of thin films by the use of the nanoscratch and nanoindentation techniques was conducted. Gold films deposited on fused quartz substrates and silicon dioxide films deposited on aluminum substrates with variant film thicknesses were investigated. These two systems correspond to a soft film on a hard substrate and a hard film on a soft substrate, respectively. The effect of substrate interaction on the measurement of hardness using the nanoscratch technique was found to be less pronounced compared to that of the nanoindentation technique due to: (i) the lower normal loads applied to achieve the penetration depths that occur at higher loads when using the nanoindentation method; (ii) the direct imaging of the residual deformation profile that is used in the nanoscratch technique, which allows for the effects of pileup or sink-in to be taken into account, whereas in the nanoindentation technique the contact area is estimated from the load-displacement data, which does not include such effects; and (iii) the account of elastic recovery of the plastically deformed surfaces from scratch tests. The film thickness did not appear to have any effect on the hardness of Au and SiO2 films obtained from nanoscratch data. This observation allowed, for the case of SiO2 films, the determination of the “free substrate effect region” and the derivation of an empirical relationship that relates the composite hardness of the film/substrate system to the contact-depth-to-film-thickness ratio, even when the indenter penetrates into the substrate. Such findings can allow for the determination of the intrinsic hardness of ultrathin hard films (∼1–5 nm thick), where the substrate effect is unavoidable.

Carbon nanotubes have been synthesized by chemical vapor deposition using a thin iron film as catalyst on the silicon substrate with different-sized rectangular patterns. It is found that the carbon nanotubes grow vertically to the substrate in a high density with a surface shape similar to that of the substrate when the line width of the patterns are larger than 1 μm, However, when the line width of the pattern is reduced to below 0.5 μm, carbon nanotubes cannot grow vertically anymore. This phenomenon might be caused by the relaxation of stress in catalyst film and the coalescence of the catalyst clusters to form particles or grains, which contributes to the migration of catalyst from edge to inner part during the nucleation process. These results are very useful for the fabrication of field-emission displays and other devices using patterned carbon nanotubes.

Sol-gel materials of aluminum-modified TiO2 of nominal composition 5.7 wt% and 10.8 wt% aluminum and aluminum/vanadium co-modified TiO2 of nominal composition 5.7Al–3.5V wt% have been prepared by evaporation of aqueous colloidal sols obtained by the hydrolysis of aqueous solutions of titanium chloride with the appropriate amount of vanadyl oxalate and/or aqueous aluminum nitrate using aqueous ammonia followed by peptization of the resulting hydrated solids using nitric acid. The nature of the sol-gel materials and the behavior upon calcination at temperatures up to 1373 K have been investigated using x-ray fluorescence, x-ray powder diffraction, transmission electron microscopy, and electron diffraction. At 333 K, all the gels comprise small (approximately 5 ± 1 nm) particles of anatase together with traces of brookite and highly crystalline ammonium nitrate. The particle size changes little on thermal treatment at 573 K, but increases significantly at higher temperatures and is accompanied by transformation to rutile. Aluminum-modified gels stabilize the anatase phase from 923 K in unmodified TiO2 to 1023 K in the 6Al/TiO2 gel and 1173 K in the 11Al/TiO2 gel. The alumina in the co-modified gel has a dominating effect on stabilizing the anatase phase until 973 K. Only rutile is present at high temperatures, except for small amounts of phase-separated α-Al2O3 (Corundum). No substitutional incorporation of Al3+ ions in the tetragonal rutile lattice occurs at high temperatures.

This study used nanoindentation coupled with stressed overlayers to evaluate the effect of titanium interlayers on the interfacial fracture energy of platinum films on SiO2 substrates. Interfacial fracture energy was calculated three ways: from platinum buckles that formed spontaneously upon deposition of the film, from buckles that formed upon deposition of a stressed tungsten overlayer, and from blisters triggered by indentation of a platinum film with a tungsten stressed overlayer. The calculated values for the interfacial fracture energy of the Pt-SiO2 interface were 0.2 and 0.5 J/m2 for indentation blisters and spontaneous buckles, respectively. The effect of a titanium interlayer on adhesion was examined using a tungsten stressed overlayer coupled with nanoindentation. The addition of a titanium layer improved the adhesion of the platinum film on SiO2 from 0.2 to 1.0 J/m2.

The tensile fracture behavior for solid-state-annealed eutectic SnPb and lead-free solder flip chip bumps was examined. The annealing temperatures were in the range of 125–170 °C for 500 h. Prior to solid state annealing, the eutectic Sn–37Pb (SnPb) and Sn–0.7Cu (SnCu) solders showed fracture through the bulk solder. Brittle interfacial fracture occurred in the Sn–3.5Ag (SnAg) solder. After solid-state annealing, the fracture behavior changed dramatically. For eutectic SnPb solder, the fracture modes gradually changed from cohesive solder failure to interfacial fracture with increasing annealing temperature. The fracture mode of the SnCu solder showed greater change than the SnPb and SnCu solders. After annealing at 125 °C, the SnAg solder had a ductile taffy pull fracture, but an increase in temperature resulted in brittle interfacial fracture again. The SnCu solder maintained the same ductile taffy pull mode up to170 °C annealing, independent of the under bump metallization (UBM) type. Microstructure analysis showed that the interfacial fracture of the SnPb and SnAg solder bumps was ascribed to Pb-rich layer formation and Ag embrittlement at the interface, respectively. The bulk solder fracture of SnAg annealed at 125 °C appeared to be a transient phenomenon due to the abrupt breakdown of the hard lamella structure. The eutectic SnCu solder bumps had no significant change in the interfacial structure, except for interfacial intermetallic growth.

Selective encapsulation of different materials or phases of a material inside a carbon nanotube leads to controlling local properties of the nanotube. We report a method of synthesizing stable γ-Fe selectively inside a carbon nanotube by transforming α-Fe through electron irradiation in situ inside a transmission electron microscope. Therefore, this method enables a single nanotube to encase both high (γ-Fe) and low (α-Fe) temperature phases of iron simultaneously. γ-Fe produced by this method may be used as a novel catalyst, and its presence inside a carbon nanotube may affect the physical properties of the nanotube, which therefore can be used to modify the nanotube.

The hardness of amorphous metal multilayered films was investigated by nanoindenation. Bilayer material systems of amorphous CuNb, FeB, and FeTi were produced by dc sputtering on 〈112￣0〉 sapphire substrates to a total thickness of 1 μm. The bilayer periods (Λ) ranged from 2 to 50 nm. The films’ noncrystallinity was verified by x-ray diffraction (XRD) and electron diffraction. The layer structure was verified by transmission electron microscopy and grazing angle XRD. The hardness and elastic modulus properties of the films, measured by nanoindentation, were shown to be statistically equivalent to the rule mixtures predictions. The hardness behavior is in contrast with the behavior of crystalline multilayered films, which generally display significant enhancements as the bilayer period is decreased below 10 nm. The lack of a significant hardness variation in the amorphous films strongly suggests that dislocation-mediated mechanisms do not govern inhomogeneous flow in amorphous metals.

New lead-free relaxors have been produced from the K0.5Na0.5NbO3–SrTiO3 (KNN-STO) system. The solid solubility within the studied range of compositions (1 - x) K0.5Na0.5NbO3–xSrTiO3 was observed for x up to 0.33. A pseudo-cubic perovskite structure was determined for x = 0.15 to 0.25. The high density and the uniform distribution of fine grains and pores were confirmed by the translucency of these ceramics. The 0.85KNN-0.15STO composition reaches the dielectric permittivity of above 3000 at room temperature. Dielectric spectroscopy measurements revealed that, as with lead-based complex perovskites, the cationic distribution disorder is reflected in relaxorlike properties, thus suggesting possible applications based on this environmentally friendly lead-free ceramic system.

The enthalpy of formation of cubic yttria-stabilized hafnia from monoclinic hafnia and C-type yttria was measured by oxide melt solution calorimetry. The enthalpies of formation fit a function independent of temperature and quadratic in composition. The enthalpies of transition from m-HfO2 and C-type YO1.5, to the cubic fluorite phase are 32.5 ± 1.7 kJ/mol and 38.0 ± 13.4 kJ/mol, respectively. The interaction parameter in the fluorite phase is strongly negative, -155.2 ± 10.2 kJ/mol, suggesting even stronger short range order than in ZrO2–YO1.5. Regular solution theory or any other model assuming random mixing on the cation and /or anion sublattice is not physically reasonable. A more complex solution model should be developed to be consistent with the new calorimetric data and observed phase relations.

Deposition of thin films via hydrothermal method has various advantages: low deposition temperature, high purity, deposition on a three-dimensional structure,and a large thickness. Although an epitaxial lead zirconate titanate (PZT) thin-film deposition has been reported, the ferroelectric measurement has not been conducted due to the peel-off morphology of the film. The current paper investigates the improvement of an epitaxial PZT thin film deposited via a hydrothermal method. By adjusting the position at which the substrate was suspended in the solution, smooth morphology surface was successfully obtained. As a bottom electrode, a 200-nm SrRuO3 thin film was deposited on SrTiO3 single crystals, and the PZT thin film was deposited on SrRuO3. The remanent polarization 2Pr and coercive electric field for PZT on SrRuO3/SrTiO3 (001) were 17.1 μC/cm2 and 36 kV/cm, respectively, and those of PZT on SrRuO3/SrTiO3 (111) were 32.7 μC/cm2 and 59 kV/cm, respectively. The reason for large imprint electrical field, 91 kV/cm and 40 kV/cm for each film, was unclear at this stage, although it is associated with self–alignment poling direction. This self–alignment poling direction was confirmed via scanning nonlinear dielectric microscopy and is thought to have been related to the deposition mechanisms.

A thin layer of SrTiO3 (STO) has successfully been used as a buffer layer to grow high-quality superconducting YBa2Cu3O7-δ(YBCO) thick films on polycrystalline metal substrates with a biaxially oriented MgO template produced by ion-beam-assisted deposition. Using this architecture, 1.5-μm-thick YBCO films with an in-plane mosaic spread in the range of 2.5° to 3.5° in full width at half-maximum and critical current density over 2 × 10 6A/cm2 in self-field at 75 K have routinely been achieved. It is interesting to note that the pulsed laser deposition growth conditions of SrTiO3 buffer layers, such as growth temperature and oxygen pressure, have strong effects on the superconducting properties of YBCO. Detailed studies using transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were used to explore the microstructures of STO deposited at different conditions and to understand further their effects on the growth and properties of YBCO films.

Calcium phosphate [single-phase hydroxyapatite (HA), single-phase tricalcium phosphate (TCP), and biphasic HA-TCP] nanowhiskers and/or powders were produced by using a novel microwave-assisted “combustion synthesis (auto ignition)/molten salt synthesis” hybrid route. This work is an example of our “synergistic processing” philosophy combining these three technologies while taking advantage of their useful aspects. Aqueous solutions containing NaNO3, Ca(NO3)2·4H2O and KH2PO4 (with or without urea) were irradiated in a household microwave oven for 5 min at 600 watts of power. The as-synthesized precursors were then simply stirred in water at room temperature for 1 h to obtain the nanowhiskers or powders of the desired calcium phosphate bioceramics.