P-type microcrystalline silicon-carbon alloy thin films have been prepared at low power by employing radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) technique; judicious choice of deposition parameters is necessary. Substrate temperature has been observed to be the most critical parameter, while high hydrogen dilution is necessary but not a sufficient condition for obtaining crystallinity in silicon-carbon alloy thin films. Best microcrystallinity at moderate power density (78 mW/cm2) has been obtained at a fairly low substrate temperature (180 °C). The highest conductivity of 5.7 Scm−1 of a boron-doped microcrystalline sample could be achieved. Incorporation of carbon in these films has been confirmed from x-ray photoelectron spectroscopic (XPS) studies. Carbon is, however, incorporated only in the amorphous phase while the crystallites are of silicon only as observed from Raman spectra.

The influence of the remnant magnetization of the soft magnetic particulates, used as a dispersed phase, on the redispersibility of magnetorheological (MR) fluids is discussed. Calculations of the magnetic interaction energy showed that for 33-vol% MR fluids based on particles of iron (∼6 μm), manganese zinc ferrite (∼2.3 μm), and nickel zinc ferrite (∼2.1 μm), the ratios of the magnetic interaction energy to the thermal energy were 161,000, 6400, and 3900, respectively. These calculations showed that even the seemingly small levels of remnant magnetization, associated with particulates employed in MR fluids, introduced significant dipole–dipole interparticle interactions. It is proposed that this interaction causes most MR fluids to show a tendency for “cake formation,” which makes it difficult to redisperse these fluids. Our modeling presented here also suggests practical strategies to enhance the redispersibility of MR fluids.

Isothermal sections at 670, 740, and 800 °C in the Cr–Ga–N ternary system were investigated. Details of the Cr–Ga and Cr–N binary phase diagrams were confirmed, and the equilibrium diagrams were constructed. At all temperatures, Cr3GaN was in equilibrium with all the condensed phases, except GaN. In the 670–800 °C temperature range, Cr2GaN appears to be kinetically stable in contact with GaN. This led to the construction of behavior diagrams that are valid only as long as GaN is present in the initial mixture. Above ∼910 °C, Cr2GaN decomposes to form Cr3GaN, CrN, and Ga(1). At 1000 °C, Cr3GaN is in equilibrium with all the condensed phases, and CrN is in equilibrium with Ga.

Chemical and electrochemical techniques were used for generating ensembles of randomly distributed organic and metal nanocylinders into the pores of nuclear track-etched polycarbonate membranes. This so-called “template method” makes it possible to synthesize a variety of materials including metals, ferromagnets, superconductors, semimetals, and conducting polymer and structures such as solid wires, tubules, composite nanostructures, and multilayers. Numerous interesting properties have been identified in relation to the nanoscopic dimensions of the materials.

Titanium carbide foams are synthesized by a self-propagation high-temperature synthesis technique using carbon black, which generates gases during the synthesis. The synthesis is performed under terrestrial and microgravity conditions. The effects of gravity on the synthesis are evaluated in this study. The foaming is mainly caused by H2O and CO gases from the carbon black. The elongation of the products increases with decreasing environmental pressure and increasing amount of generated gases. Since the gas flows out along the direction of the combustion wave propagation, the products expand only along this direction. The propagation velocity of the combustion wave increases with increasing amount of generated gases and environmental pressure, which is due to the amount of molten Ti transporting into the reaction/preheat zone. Under higher environmental pressures, thermal convection of the environmental gases mainly affects the propagation velocity. However, at lower pressures, the behavior of the molten Ti has a great effect compared with the gases surrounding the specimens.

The bombarding energy dependence of bonding structure in amorphous carbon interlayer and its effect on diamond nucleation density (Nd) were studied. Amorphous carbon (a-C) interlayer was deposited by magnetron sputtering. Interestingly, the intensity ratio (ID/IG) of the D band (∼1400 cm−1) to the G band (∼1570 cm−1) in the Raman spectra and the optical band gap of the a-C film were found to be inversely proportional to the sputtering power, that is, to bombarding energy. When diamond was subsequently deposited at 800 °C by microwave plasma chemical vapor deposition (CVD), diamond could be grown only on the interlayers with higher ID/IG (≥2.20), and Nd was increased up to 2 × 106/cm2 with the increase of ID/IG ratio, that is, with the decrease of the bombarding energy. We experimentally confirmed that the amount of the sp3 bonded carbon clusters within the interlayer was dependent on the bombarding energy of the particles, determining the diamond nucleation density. We suggest that the transformation of the amorphous carbon into graphitic carbon should be effectively prevented for the diamond nucleation on the a-C interlayer.

An attempt has been made to interpret the experimentally reported transitions of layer sequences during the Co/Si, Ti/Si, and Ni/Si interfacial reactions in a consistent way, and to build a thermodynamic calculation scheme that enables it. The basic ideas are that the silicide with the highest driving force of formation under a metastable local equilibrium state at an interface would form first at the lowest temperature, and that when several silicides can nucleate simultaneously and compete for growth at an initial stage of a high temperature reaction, the one whose composition is closest to those of surrounding phases would form a continuous interfacial layer first and grow thicker. A critical review of literature information has also been made in order to clarify the first-forming silicide and silicide formation sequence in each metalySi interfacial reaction. The observed first-forming crystalline silicides, CoSi, Ti5Si3, and Ni2Si, in each metalySi interfacial reaction were in agreement with the present prediction based on the first idea. The reason why Co2Si and C49 TiSi2 have frequently been observed in high temperature Co/Si and TiySi reactions as if they were the first-forming crystalline silicides could also be explained based on the second idea. By combining both ideas, a general thermodynamic calculation scheme that can be applied for analysis, rationalization, and even prediction of interfacial reactions between different materials could be suggested.

Nanostructured yttria powders were prepared by a gel combustion technique. The technique involves exothermic decomposition of an aqueous citrate-nitrate gel. The decomposition is based on a thermally induced anionic redox reaction. A variety of yttria powders with different agglomerate structures can be made by altering the citrate-nitrate ratio γ. The gel with γ = 0.098 in situ yields nanostructured yttria powder at 258 °C that is porous and agglomerated with an average of 25 nm primary particles. Its specific surface area is 55 m2/g. The decomposition of the gels was investigated by simultaneous thermogravimetry analysis (TGA) and differential thermal analysis (DTA) experiments. The produced ashes and calcined powders are characterized by x-ray diffraction (XRD), ir spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer, Emmett, and Teller (BET) analysis.

The effects of substrate cleaning, nitridation time, and substrate temperature in the range 800–1000 °C on the microstructure of AlN/Si(111) films grown by simultaneous plasma-assisted molecular beam epitaxy have been investigated. It has been demonstrated, using a combination of conventional and high-resolution transmission electron microscopy, that the interface structure, the film defect structure, and the film surface roughness are strongly related. The formation of single crystal 2H–AlN films with atomically flat surfaces occurs at 800 °C for conditions of 2.5 nm/min growth rate on very pure, atomically flat Si substrates.

We have investigated the effect of RuO2 (10, 30, 50 nm)/Pt layered hybrid bottom electrode structure and film composition on the leakage and fatigue properties of chemical solution derived Pb(ZrxTi1−x)O3 (PZT) thin films. It was observed that the use of high Ti content (Zr: Ti = 30: 70) films with control of excess PbO at the thin RuO2 (10 nm)/Pt bottom electrode surface reduced leakage current and showed good fatigue properties with high remanent polarization compared to the use of high Zr films (Zr: Ti = 50: 50) or thicker RuO2 (30, 50 nm)/Pt bottom electrodes. Typical P-E hysteresis behavior of PZT films was observed even at an applied voltage of 3 V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics of these modified PZT thin films (Zr: Ti = 30: 70) on RuO2 (10 nm)/Pt, measured at 5 V, showed stable behavior, and less than 15% fatigue degradation was observed up to 1010 cycles.

Oxidation of polycrystalline nickel particles with an approximate median diameter of 158 μm has been studied by thermogravimetric measurements in the temperature range 773–1473 K. The oxidation was found to be thermally activated with an apparent activation energy of about 1.9 eV at temperatures below 1073 K and 1.2 eV at higher temperatures. Our data showed the qualitative features expected for oxidation of spherical metal particles. The kinetics was compared with a homogenous field coupled-currents theory for oxidation of spherical metal particles. Calculations using a median particle size or a distribution of particle sizes could only give a satisfactory fit to part of the experimental data. Possible explanations for the deviations in terms of space charge, grain boundary diffusion, grain growth, and sintering are discussed in this paper. Scanning electron microscopy studies of the particles after oxidation showed that a large difference exists in the surface structure and the degree of sintering between the particles oxidized at low and high temperatures.

Carbon nanotubes produced by the treatment of Mg1−xMxAl2O4 (M = Fe, Co, or Ni; x = 0.1, 0.2, 0.3, or 0.4) spinels with an H2–CH4 mixture at 1070 °C have been investigated systematically. The grains of the oxide-metal composite particles are uniformly covered by a weblike network of carbon nanotube bundles, several tens of micrometers long, made up of single-wall nanotubes with a diameter close to 4 nm. Only the smallest metal particles (<5 nm) are involved in the formation of the nanotubes. A macroscopic characterization method involving surface area measurements and chemical analysis has been developed in order to compare the different nanotube specimens. An increase in the transition metal content of the catalyst yields more carbon nanotubes (up to a metal content of 10.0 wt% or x = 0.3), but causes a decrease in carbon quality. The best compromise is to use 6.7 wt% of metal (x = 0.2) in the catalyst. Co gives superior results with respect to both the quantity and quality of the nanotubes. In the case of Fe, the quality is notably hampered by the formation of Fe3C particles.

Ideal spherical nonagglomerated Ni particles (mean diameter 0.62–1.12 μm) were prepared by ultrasonic spray pyrolysis of NiCl2 aqueous solution in the presence of 0.1 mass% of Pd, Cu, or Ni in an H2–N2 atmosphere at 900 °C. Incomplete reduction of the NiCl2 aqueous solution in the absence of additives was observed under the same conditions. Differential thermal and thermal-gravimetric analyses revealed a decrease in initial reduction temperature of NiCl2 from 375 to 275 °C by the addition of Pd, Cu, or Ni. The morphology of Ni particles was analyzed using scanning tunneling microscopy. The surface roughness of Ni particles was found to be controllable by addition of appropriate additives.

Polycrystalline SrBi2Nb2O9-layered ferroelectric thin films were synthesized on Pt/Ti/SiO2/Si substrate using the polymeric precursors solution. The dip-coated films were specular and crack-free and crystallized during firing at 700 °C. Single-, double-, and triple-layered films were obtained by several dips in the deposition solution, and the influence of crystallization between each dip was studied. Microstructure and morphological evaluation were followed by grazing incident x-ray diffraction (GIXRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Multilayered films obtained using the intermediate-crystallized layer route present a dense microstructure with spherical grains, with a preferential orientation in the 〈215〉 direction; films obtained using the intermediate-amorphous layer route are polycrystalline and present elongated grains around 250 nm in size.

Ultrathin and uniform Pt-silicide layers are prepared by electron beam evaporation on a heated silicon substrate and by magnetron sputtering at room temperature followed by rapid thermal annealing (RTP) and selective etching, respectively. In the electron-beam deposited samples, continuous Pt-silicide layers of 6–8 nm thickness are formed after thermal annealing. The interfaces between the silicide layers and the silicon substrate are not atomically flat. In the case of the sputtered Pt, continuous PtSi layers down to 3 nm thick can be produced by using two-step (low-high temperature) and modified two-step (selective etch and high-temperature anneal) RTP silicidation processes. In one-step (high-temperature) processed samples, PtSi is the dominant phase; meanwhile, a small fraction of Pt12Si5 phase is inhomogeneously distributed in the case of thicker PtSi layers. In the two-step RTP processed samples, a Pt/Pt2Si/PtSi/Si layered structure is formed after the first RTP step. The first anneal step is found to be crucial for the roughness and epitaxy of the final PtSi layer. The best Schottky barrier heights are found to be 0.249 eV for the 3 nm PtSi/p-Si(100) Schottky diodes. The e-beam and the sputtered PtSi layers follow different epitaxial growth models.

In this paper, a new hydrothermal method—discharging-gas method—is introduced. ZnO acicular particles with the ratio of length and diameter 16: 1 are synthesized by the hydrothermal discharging-gas method using a mixed solution of Zn(CH3COO)2 with NaNO2 as precursor at 190 °C for 1 h. The effects of reaction temperature and precursor concentration on formation of acicular particles are investigated. The results show that the main factor for formation of acicular particles prepared by the hydrothermal discharging-gas method is the extent of crystallinity of ZnO powders before releasing gas.

A low-temperature (>450 °C) thermal chemical vapor deposition (CVD) process was developed for the growth of TaNx from the reaction of tantalum pentabromide, ammonia, and hydrogen. Studies of process reaction kinetics yielded two sequential rate-controlling steps, with an activation energy of 0.45 eV for the kinetically limited reaction regime. Additionally, a systematic design of experiments approach examined the effects of key process parameters, namely, substrate temperature, source temperature, and hydrogen and ammonia flows, on film properties. A wide CVD process window was established for nitrogen-rich amorphous TaNx with contamination below 1 at.%. Film conformality was higher than 95% in nominally 0.30 μm, 4.5: 1 aspect ratio, trench structures.

Structure and composition of the ferroelectric Pb(Zr, Ti)O3 layers in a capacitor of the ferroelectric random-access memory (FeRAM) device having a density of 64 k were investigated by transmission electron microscopy (TEM) together with the energy-dispersive spectroscopy (EDS) technique. The 250 nm thick PZT layer derived by the sol-gel route showed a 2–3% Pb-deficient, 3–4% Ti-deficient, and 5–7% Zr-excess composition at the top electrode interface compared to the bulk composition when they were as-fabricated. The local compositional nonuniformity became more critical as the integration process proceeded, which seriously degraded the ferroelectric hysteresis and the device yield. The major cause of the compositional variation was the outward diffusion of Pb through the capping barrier TiO2 layer during annealing at 650 °C. The AlN capping barrier layer was also not effective in suppressing the diffusion of Pb. However, the Al2O3/TiO2 double capping layer was very effective in suppressing the outward diffusion of Pb, and excellent ferroelectric characteristic was expected.

The orientation relationship and the interfaces of ZrO2(c)–CaZrO3 unidirectional solidified eutectics have been investigated by means of electron diffraction and transmission electron microscopy (TEM). In contrast to previous studies on lamellar oxide-oxide systems, neither a constant orientation relationship between contiguous lamellae nor low-index interfaces are observed in this eutectic. As for metals and plastic crystals, it displays incoherent interfaces and nonfaceted growth. This unusual behavior is discussed in terms of entropy of fusion and related to the presence of oxygen vacancies in the ZrO2(c) phase.

Single Ti layers, single TiN layers, and thin Ti films overlayered with Au were investigated as ohmic contacts to n-type (n 4.5 × 1017 to 7.4 × 1018 cm−3) single-crystal GaN (0001) films. Transmission line measurements (TLM) revealed the as-deposited TiN and Au/Ti contacts on n = 1.2 − 1018 cm−3 to be ohmic with room-temperature specific contact resistivities of 650 and 2.5 × 107minus;5 Ω cm2, respectively. Single Ti layer contacts had high resistance and were weakly rectifying in the as-deposited condition. The three contact/GaN systems exhibited a substantial decrease in resistivity after annealing; the value of ρc was also a function of the carrier concentration in the GaN. The Au/Ti contacts exhibited the lowest resistivity values yet observed in these contact studies, particularly for the more lightly doped n-GaN. The ρc for n = 1.2 × 1018 cm−3 reached 1.2 × 1026 Ω cm2; for n = 4.5 × 1017 cm−3, ρc = 7.5 × 1025 Ω cm2 after annealing both samples through 900 °C. X-ray photoelectron spectroscopy (XPS) and high-resolution cross-sectional transmission electron microscopy (X-TEM) analysis revealed the formation of TiN at the interface of annealed Ti layers in contact with GaN, which is believed to be beneficial for ohmic contact performance on n-GaN.