The catalytically important, two-dimensional vanadyl hydrogen phosphate hemihydrate, VOHPO4·0.5H2O phase was transformed to the one-dimensional vanadyl hydrogen phosphate tetrahydrate, VOHPO4·4H2O for the first time by mild treatment with water vapor. It was also observed that for three samples of VOHPO4·0.5H2O prepared under different conditions, the rate of transformation to the tetrahydrate was markedly affected by morphology and crystallinity. The tetrahydrate phase could also be re-transformed to the hemihydrate by applying high vacuum or by heating at 120 °C, but this was accompanied by significant loss in crystallinity.

Void evolution during electromigration was studied by recording void nucleation, growth, and displacements at various intervals during thermal (240 °C) and electrical stress tests (2 × 106 amps/cm2) of Cu interconnects. Structural data was collected for various serially arranged line segment lengths and correlated with resistance and increases in resistance due to electromigration-induced thinning and voiding. These results allowed determination of void growth rates in Cu interconnects. Void nucleation and growth show a clear dependence on segment length. Void formation did not occur at the via/interconnect interface, which improved interconnect reliability by allowing extensive voiding before catastrophic failure.

An accurate and reliable electrical technique for continuous monitoring of crack growth in fracture specimens containing technologically relevant thin-film device structures has been developed. Both adhesive and cohesive crack growth measurements are reported using a SiO2 passivation layer and a conducting titanium film deposited on the side face of fracture specimens. Crack velocity measurements approaching 10−12 m/s were achieved, representing nearly an order of magnitude improvement over commonly used compliance-based techniques. The technique may be particularly useful for elucidating near threshold crack velocity behavior, which is important for thin-film reliability.

Tubular and capsular needlelike crystals of C60 with a few hundreds nanometers to about one micrometer in diameter were discovered among the precipitates prepared by the liquid–liquid interfacial precipitation method. Addition of a small amount of (η2–C60)Pt(PPh3)2 to the toluene solution of C60 produced various morphologies of hollow C60 crystals. This paper gives the first report on the formation of structures we named “C60 nanotubes.”

First, a grating decay rate and a thermal diffusion rate of the transient gratings are determined out of the energy-time trace observed by using a transient grating technique with 266-nm laser pulse inducing transient gratings in a LaCoO3 thin film. Second, the grating models aimed at studying two different thermal diffusion phenomena in contrast with the previous paper are described. The difference between both phenomena is attributable to the volume of photon scattering to characterize induced transient gratings. It is concluded that a reliable energy-time trace is observed when the transient gratings with a thickness smaller than a film are induced on the very surface of a thin film sample.

Materials with preferred orientation exhibit unique properties that are frequently improved in comparison with those that are randomly oriented. Optical waveguide devices require high-quality single-crystal–like thin films because of their low optical propagation loss and their near–single-crystal properties. The growth mechanisms of textured films on non-lattice matched amorphous substrates, such as glass, are different from those on single-crystal substrates or the surface of a metal electrode. In this study, highly (100) oriented Pb(Zr,Ti)O3 PZT films were grown on an amorphous substrate by means of the sol-gel multicoating method, using lanthanum nitrate as a buffer layer. The lanthanum nitrate buffer layer was also very effective as a diffusion barrier against Pb-Si interdiffusion. The electrooptic properties of the PZT films were markedly enhanced when their orientation was adjusted to the (100) direction.

CdSe magic-sized nanoclusters were synthesised at relatively low temperatures (90–150 °C) in the organometallic raw material solution by a very simple method. The variation process from nanoclusters to nanocrystals has been determined using the microreactor, and it was found that these nanoclusters could increase the CdSe nuclei number and product yield in the microfluidic reactor method. Meanwhile, the microreactor shows the advantage for studying the nanocrystal-growth process due to the precise time and temperature control and high reproducibility.

Nanocrystalline CeO2 powder was synthesized by a citrate-nitrate autoignition process and characterized by thermal analysis, x-ray diffraction, and impedance spectroscopy measurements. Nanocrystalline (20–40 nm) ceria powder with fluorite structure had formed in situ during the citrate-nitrate autoignition process. The powder prepared could be sintered to density more than 98% of theoretical density at 1450 °C. The nanocrystalline CeO2 exhibited an increase in conductivity in Ar and H2 than air above 600 °C, suggesting a possible electronic contribution to the conductivity at low oxygen partial pressures. Impedance measurements on the sintered samples unequivocally established the potential of this process in developing phase pure ceria compositions.

By using molecular dynamics simulations, we have accurately determined the true contact area during plastic indentation of materials under an applied in-plane stress. We found that the mean pressure calculated from the true contact area varied slightly with applied pre-stress with higher values in compression than in tension and that the modulus calculated from the true contact area is essentially independent of the press-stress level in the substrate. These findings are largely consistent with the findings of Tsui, Pharr, and Oliver. On the other hand, if the contact area is estimated from approximate formulae, the contact area is underestimated and shows a strong dependence on the pre-stress level. When it is used to determine mean pressure and modulus, the empirically determined area leads to large errors. Our simulations demonstrate that this phenomenon, first reported for macroscale hardness measurements dating back to 1932, also exists at the nanometer-scale contact areas, apparently scaling over 10 orders of magnitude in contact area, from ∼mm2 to ∼100 nm2.

The title compositions were prepared by the gel-combustion process using glycine as the fuel and the corresponding metal nitrates as oxidants. The powders after calcination at 600 °C were characterized by x-ray diffraction for phase identification. The lattice parameters were refined by least squares method for each of the title compounds. Sr0.09Ce0.91O1.91 could be prepared in situ, that is, without any further external heating at higher temperatures, whereas phase pure SrCeO3 and Sr2CeO4 could be prepared only after calcination at 950 °C for 3 h. Sr0.09Ce0.91O1.91 was prepared using three different oxidant-to-fuel ratios: the fuel-deficient ratio, the propellant chemistry (stoichiometric) ratio, and the fuel-excess ratio. The crystallite size as calculated by x-ray line broadening was found to be 13 nm, 20 nm, and 42 nm for the products from fuel-deficient, propellant, and fuel-excess ratios, respectively. It was found that the extreme fuel-deficient ratio of 1:0.5 failed to give phase pure Sr0.09Ce0.91O1.91. The transmission electron microscopy studies showed that majority of the particles were in the range 80–100 nm and 200–250 nm for SrCeO3 and Sr2CeO4, respectively. The compositional characterization was done by energy dispersive x-ray. A careful control of the oxidant-to-fuel ratio was found to be necessary to get the desired products, due to their different thermodynamic stabilities. Thus, the versatility of combustion process in synthesizing the products with different thermodynamic stabilities has been shown, which was hitherto unexplored.

Ti1−XSbXO2 samples were obtained from dip-coating sol-gel method and a subsequent anneal at 450 °C. They had an average crystallite size of 13.3–20 nm. Cyclic voltammograms taken under ultraviolet (UV) and Xe lamp illumination in a 0.5 M Na2SO4 electrolyte showed that the Sb-doped samples had greater photocurrent densities than pure titania electrode, with an optimal Sb concentration of 0.2%. Oxidative peaks were observed in the cyclic voltammograms obtained in the dark after certain exposure duration to UV light. X-ray diffraction patterns and Raman spectra show a phase transformation from brookite to anatase in the samples with Sb concentration up to 0.2%. Ti4+ ions were substituted by Sb to form the anatase structure of Sb–O–Ti, improving the crystallization efficiency. The Sb–Sb bonds were formed due to the introduction of excessive Sb atoms.

About 1.5-μm-thick single-layer TiN, CrN, TiAlN coatings and nanolayered TiN/CrN, TiAlN/CrN multilayer coatings were deposited on silicon (111) substrates using a reactive direct current magnetron sputtering process. Structural characterization of the coatings was done using x-ray diffraction (XRD) and micro-Raman spectroscopy. All the coatings exhibited NaCl B1 structure in the XRD data. Raman spectroscopy data of as-deposited coatings exhibited two broad bands centered at 230–250 and 540–630 cm-1. These bands have been assigned to acoustical and optical phonon modes, respectively. Thermal stability of the coatings was studied by heating the coatings in air in a resistive furnace for 30 min in the temperature range 400–900 °C. Structural changes as a result of heating were characterized using Raman spectroscopy and XRD. Raman data showed that TiN, CrN, TiN/CrN, TiAlN, and TiAlN/CrN coatings started to oxidize at 500, 600, 750, 800, and 900 °C, respectively. To isolate the oxidation-induced spectral changes as a result of heating of the coatings in air, samples were also annealed in vacuum at 800 °C under similar conditions. The Raman data of vacuum-annealed coatings showed no phase transformation, and intensity of the optical phonon mode increased and shifted to lower frequencies. The origin of these spectral changes is discussed in terms of defect structure of the coatings. Our results indicate that the thermal stability of nanolayered multilayer coatings is superior to the single-layer coatings.

Polycrystalline diamond films with a predominant (100) texture were deposited onto silicon substrates using hot-filament chemical vapor deposition. During film deposition, different temperature gradients were created and imposed laterally across the substrate materials. Films grown under a gradient of 100 °C cm−1 displayed large (100) oriented grains. No crystallite (100) orientation was observed in the as-grown films prepared without a temperature gradient. It was observed that the diamond grain size varied as a function of the gradient. The lower gradient resulted in smaller grains and vice versa. Furthermore, the size of the grains was a function of the deposition time. The orientation of the diamond grains changed gradually across the substrate from (100) to (110) orientation as we scanned from the high-temperature to the low-temperature zone. The films were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. XRD showed strong (400) reflections in the oriented samples. SEM results indicated the presence of smooth diamond surfaces consisting of predominantly (100) oriented platelets. As the (100) oriented diamond grains were grown on top of the (100) oriented silicon substrates, the faces were mostly aligned parallel to the substrate surface resulting in the deposition of a smooth diamond surface. AFM observations revealed the presence of steps located at the boundaries of the oriented grains. FTIR results showed the characteristic difference in hydrogen bonding in the oriented samples and gave useful information about mechanisms responsible for the orientation. Quantitative analysis was carried out to measure the H content in the films, and it was found that the oriented films contained less hydrogen. Our findings suggest that high saturation of carbon and a concentration gradient of sp3 CH2 species can be the key factor in the oriented growth of (100) diamond grains.

When lead-free solder alloys mix with lead-free component and board metallizations during reflow soldering, the solder interconnections become multicomponent alloy systems whose microstructures cannot be predicted on the basis of the SnPb metallurgy. To better understand the influences of these microstructures on the reliability of lead-free electronics assemblies, SnAgCu-bumped components were reflow-soldered with near-eutectic SnAgCu solder pastes on Ni(P)|m.Au- and organic solderability preservative (OSP)-coated printed wiring boards and tested under cyclic thermal shock loading conditions. The reliability performance under thermomechanical loading was found to be controlled by the kinetics of recrystallization. Because ductile fracturing of the as-soldered tin-rich colonies would require a great amount of plastic work, the formation of continuous network of grain boundaries by recrystallization is needed for cracks to nucleate and propagate intergranularly through the solder interconnections. Detailed microstructural observations revealed that cracks nucleate and grow along the grain boundaries especially between the recrystallized part and the non-recrystallized part of the interconnections. The thermal cycling test data were analyzed statistically by combining the Weibull statistics and the analysis of variance. The interconnections on Ni(P)|m.Au were found out to be more reliable than those on Cu|m.OSP. This is due to the extensive dissolution of Cu conductor, in the case of the Cu|m.OSP assemblies, into molten solder that makes the microstructure to differ noticeably from that of the Ni(P)|m.Au interconnections. Because of large primary Cu6Sn5 particles, the Cu-enriched interconnections enhance the onset of recrystallization, and cracking of the interconnections is therefore faster. The solder paste composition had no statistically significant effect on the reliability performance.

We present a supercritical CO2 (SCCO2) process for the preparation of nanoporous organosilicate thin films for ultralow dielectric constant materials. The porous structure was generated by SCCO2 extraction of a sacrificial poly(propylene glycol) (PPG) from a nanohybrid film, where the nanoscopic domains of PPG porogen are entrapped within the crosslinked poly(methylsilsesquioxane) (PMSSQ) matrix. As a comparison, porous structures generated by both the usual thermal decomposition (at approximately 450 °C) and by a SCCO2 process for 25 and 55 wt% porogen loadings were evaluated. It is found that the SCCO2 process is effective in removing the porogen phase at relatively low temperatures (<200 °C) through diffusion of the supercritical fluid into the phase-separated nanohybrids and selective extraction of the porogen phase. Pore morphologies generated from the two methods are compared from representative three-dimensional (3D) images built from small-angle x-ray scattering (SAXS) data.

Al2O3–(m-ZrO2)/t-ZrO2 composite having fibrous and homogeneous microstructure was successfully fabricated using a fibrous monolithic process. The composites had a homogeneous microstructure as well as good interfaces between the Al2O3–(m-ZrO2) and t-ZrO2 phases. The thickness of each phases were reduced to 375, 50, 5 μm, and 0.7 μm as the number of extrusion passes increased up to 5. The material properties of density, hardness, bending strength, and fracture toughness increased as the passes of extrusion were increased up to a fifth pass, and their maximum values were about 98.5%, 1230 Hv, 570 MPa, and 6.5 MPa⋅m1/2, respectively. The fracture toughnesses in the direction of longitudinal and transverse direction of the fifth passed sample showed the different values with about 6.5 and 5.4 MPa⋅m1/2, respectively.

The effects of different particle size distributions on the real-time hydration of tricalcium silicate cement paste were studied in situ by quasi-elastic neutron scattering. The changing state of water in the cement system was followed as a function both of cement hydration time and of temperature for different initial particle size distributions. It was found that the length of the initial, dormant, induction period, together with the kinetics of hydration product nucleation and growth, depends on the hydration temperature but not on the particle size distribution. However, initial particle size does affect the total amount of cement hydrated, with finer particle size producing more hydrated cement. Furthermore, the diffusion-limited rate of hydration at later hydration time is largely determined by the initial tricalcium silicate particle size distribution.

The sintering of nanosize powders of fully stabilized zirconia was investigated using the spark plasma sintering (SPS) method. The influence of sintering temperature, heating rate, direct current pulse pattern, sintering time, and sintering pressure on the final density and grain size of the product was investigated. The dependence of densification on temperature showed a maximum at 1200 °C, resulting with nearly fully dense zirconia with a crystallite size of about 100 nm. Heating rate (50∼300 °C min−1) and sintering time (5–16 min) had no significant influence on the final density and the crystallite size. Pulsing patterns ranging from 2:2 to 48:2 (on:off) had no influence on the density or the crystallite size. However, the applied pressure had a significant influence on the final density but no apparent effect on crystallite size for a sintering temperature of 1200 °C and a hold time of 5 min.

Dense fully stabilized cubic zirconia, sintered by the spark plasma sintering (SPS) method, was characterized through hardness, fracture toughness, and electrical impedance measurements. The effect of sintering temperature on hardness and fracture toughness was evaluated. Samples sintered at 1200 °C for 5 min, which had crystallite size of <100 nm, exhibited the highest hardness. Impedance measurements showed an increase in bulk contribution relative to grain boundaries as sintering temperature is increased. Calculation of the activation energy for conduction gave a value, 1.13 eV, in agreement with previously published results.

Dense β–Si3N4 ceramics were fabricated from α–Si3N4 raw powder by gas-pressure sintering at 1900 °C for 12 h under a nitrogen pressure of 1 MPa, using four different kinds of additive compositions: Yb2O3–MgO, Yb2O3–MgSiN2, Y2O3–MgO, and Y2O3–MgSiN2. The effects of additive composition on the microstructure and thermal and mechanical properties of β–Si3N4 ceramics were investigated. It was found that the replacement of Yb2O3 by Y2O3 has no significant effect on the thermal conductivity and fracture toughness, but the replacement of MgO by MgSiN2 leads to an increase in thermal conductivity from 97 to 113 Wm-1K-1and fracture toughness from 8 to 10 MPa m1/2, respectively. The enhanced thermal conductivity of the MgSiN2-doped materials is attributed to the purification of β–Si3N4 grain and increase of Si3N4–Si3N4 contiguity, resulting from the enhanced growth of large elongated grains. The improved fracture toughness of the MgSiN2-doped materials is attributed to the increase of grain size and fraction of large elongated grains. However, the same thermal conductivity between the Yb2O3- and Y2O3-doped materials is related to not only their similar microstructures, but also the similar abilities of removing oxygen impurity in Si3N4 lattice between Yb2O3 and Y2O3. The same fracture toughness between the Yb2O3- and Y2O3-doped materials is consistent with their similar microstructures. This work implies that MgSiN2 is an effective sintering aid for developing not only high thermal conductivity (>110 Wm−1K−1) but also high fracture toughness (>10 MPa m1/2) of Si3N4 ceramics.