The photoluminescence of terbium-activated yttrium silicate with the general formula Y2−XTbxSiO5 was investigated as a function of Tb3+ concentration. Especially, the main attention was focused on the 5D3 fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb3+ concentration. The diffuse reflectance spectrum was also measured in the range from VUV to UV. As a result, yttrium silicate was found to have a broad absorption band extended from the VUV to UV range. The concentration quenching was investigated in terms of luminance and decay time both for 5D3 and 5D4 fluorescence. The energy transfer was also investigated by analyzing the decay curve of 5D3 emission on the basis of the multipolar interaction. The decay curves of 5D3 emission, for which well-known cross-relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula on the basis of the direct quenching scheme. Furthermore, the rate equations including a newly proposed quenching scheme were taken into consideration. The rate equations accept the emission quenching as due to the cross-relaxation from 5D3 or 4 to some upper levels such as 7D and the charge-transfer band.

Cuprous oxide (Cu2O) films have been grown on single-crystal MgO(110) substrates by a chemical vapor deposition process in the temperature range 690–790 °C. X-ray diffraction measurements show that phase-pure, highly oriented Cu2O films form at these temperatures. The Cu2O films are observed to grow by an island-formation mechanism on this substrate. Films grown at 690 °C uniformly coat the substrate except for micropores between grains. However, at a growth temperature of 790 °C, an isolated, three-dimensional island morphology develops. Using a transmission electron microscopy and atomic force microscope, both dome- and hut-shaped islands are observed and are shown to be coherent and epitaxial. The isolated, coherent islands form under high mobility growth conditions where geometric strain relaxation occurs before misfit dislocation can be introduced. This rare observation for oxides is attributed to the relatively weak bonding of Cu2O, which also has a relatively low melting temperature.

Mixed-phase compositions in the Bi2O3–ZnO–Nb2O5 pyrochlore system have been previously identified as potential low-fire dielectric composites for high-frequency multilayer devices. However, there has been a problem with the ability to co-process this material with silver. It was found that an intermediate BiNbO4 phase that occurs during calcination can interact with silver during co-sintering, forming a deleterious phase. Processing routes to control the presence of remanent BiNbO4 were investigated, such as ZnO stoichiometric adjustment, low partial pressure of oxygen sintering atmosphere, and specific temperature-time dwells.

An amorphous boron–carbon–nitrogen (a-BCN) phase was synthesized by ball milling of a mixture of hexagonal BN (h-BN) and graphite with a nominal composition of (BN)0.5C0.5 in atomic ratio. Electron energy-loss spectroscopy studies indicated that the bonding of the a-BCN is in an sp2 configuration and the mixing between the BN and the C species was achieved at a nanometer scale, but the a-BCN phase was more likely a mechanical mixture rather than a chemical mixture. High-pressure and high-temperature (HPHT) treatment at 7.7 GPa and 2300 °C of the a-BCN phase resulted in complete segregation of the carbon and BN species, forming a nanocrystalline composite material comprising cubic BN (c-BN), amorphous carbon, and turbostratic graphite. The grain size of the c-BN phase was about 70 nm. No mutual solubilities between c-BN and carbon were found, and the two different species (C and BN) were well separated. An epitaxial relationship, i.e., the (0002) planes of graphite being parallel to the (111) planes of c-BN, was also found. The formation of ternary BCN phases was never found in the present experiment. Our experimental results also suggest the possibility of synthesizing c-BN grains encapsulated with graphite under controlled HPHT conditions.

We developed p-type μc-silicon carbon alloy thin films by the very high frequency plasma-enhanced chemical vapour deposition technique using a SiH4, H2, CH4, and B2H6 gas mixture at low power (55 mW/cm2) and low substrate temperatures (150–250 °C). Effects of substrate temperature and plasma excitation frequency on the optoelectronic and structural properties of the films were studied. A film with conductivity 5.75 Scm−1 and 1.93 eV optical gap (E04) was obtained at a low substrate temperature of 200 °C using 63.75 MHz plasma frequency. The crystalline volume fractions of the films were estimated from the Raman spectra. We observed that crystallinity in silicon carbon alloy films depends critically on plasma excitation frequency. When higher power (117 mW/cm2) at 180 °C with 66 MHz frequency was applied, the deposition rate of the film increased to 50.7 Å/min without any significant change in optoelectronic properties.

We have developed a molecular-dynamics technique for determining the adhesion strength of the interfaces between different materials. This technique evaluates the adhesion strength by calculating the adhesive fracture energy defined as the difference between the total potential energy of the material-connected state and that of the material-separated state. The extended Tersoff-type potential is applied to calculate the adhesive fracture energy of metal/dielectric interfaces as well as metal/metal interfaces. We used the technique to determine the adhesion strength of the interfaces between ULSI-interconnect materials (Al and Cu) and diffusion-barrier materials (TiN and W). It was also applied to determine the adhesion strength of interfaces between the interconnect materials and a dielectric material (SiO2). Because the adhesion strength determined by this technique agrees well with that measured by scratch testing, this technique is considered to be effective for determining the adhesion strength.

Ca-α-sialon compacts pressureless-sintered to intermediate temperatures, which consisted of both α-sialon and unreacted α–Si3N4 grains, were investigated with transmission electron microscopy for an overall composition Ca1.8Si6.6Al5.4O1.8N14.2. Special attention was paid to identification of the possible crystallographic orientation between a-sialon and the α–Si3N4 particles. In contrast to the frequently occurring heteroepitaxial nucleation of α-sialon in rare-earth-doped samples with low x values, this study showed that most of the newly formed α-sialon grains had no epitaxial orientation relationship with the α–Si3N4 particles, suggesting nonepitaxial heterogeneous nucleation to be a more probable mechanism for the Ca–α-sialon phase with high Ca concentrations.

Oxides with significant mesopore volume can be produced from gels through ambient pressure drying (APD) if the oxide network within the gel is sufficiently strong. To obtain a strong alumina gel, a commercial alumina powder (100 nm diameter) was combined with different amounts of ethanol, water, and acid. Significant mesoporosity was observed in dried and calcined gels prepared from this precursor and ethanol alone, particularly when “poor wettability” was established in the gel through azeotropic distillation in toluene. When water (or water and nitric acid) was also utilized the pore volume decreased dramatically; this observation may be attributed to the creation of amorphous alumina from the crystalline precursor that is displaced into the interparticle pores, and in which mesopores are poorly preserved during APD.

The sessile-drop method and high-temperature small-angle x-ray diffraction technique were used to characterize the density of liquid Al–Si alloys with Si content C = 0 to 22 wt%. A distinct abnormal volume expansion of the hyper-eutectic melts was identified just above the liquidus (within TL–Tk) during the heating sequence (h.s.), which is irreversible during the cooling sequence (c.s.). This phenomenon is explained by the segregation of Si atoms from the supersaturated “quasi-eutectic” structure and formation of silicon clusters in the superheated melt. In addition, a pre-peak in the x-ray diffraction spectrum of Al–14% Si melt was observed at 850 °C, which is associated with the silicon clusters. The pre-peak remains when the superheated melt is cooled down to the liquidus (670 °C); this result is in accord with the density measurements.

The effect of fiber texture on the x-ray residual stress analysis in thin films of cubic materials is discussed according to different mechanical models. The x-ray elastic constants (XECs) were calculated from single-crystal elastic constants for Cu, cubic ZrO2, and TiN, in the case of a typical [111] fiber texture with different spread of orientations [expressed by the half-width at half-maximum of the (111) pole figure]. Calculations were performed according to Reuss, Voigt, and Hill models, considering different crystallographic directions in cubic structures, in order to underline the effect of the mechanical anisotropy and fiber texture. The results clearly indicated the dependence of the XECs on the sample tilting angle, with the notable exception of [111] and [200], which were texture oscillation-free directions. Profiting from this condition the residual stress gradient in a fiber-textured TiN thin film deposited on stainless steel was determined by the simultaneous analysis of texture and residual strain for the (111) and (200) reflections. Advantages and limits of the procedure are discussed together with the experimental results.

The alignment degree of sintered Nd–Fe–B magnets and its dependence on applied field and compacting mode were studied by magnetic force microscopy. By analyzing the magnetic force images to illustrate the magnetic-domain structure, an experimental method for quantitatively evaluating the alignment degree of sintered Nd–Fe–B magnets was given. The results show that if the compacting mode is the same, the alignment of magnets will be better as field increases. Under the same field, the alignment degree for rubber isostatic pressing with vibration is better than that for nonmagnetic metal die pressing. However, if the sample is compacted by rubber isostatic pressing without vibration, the alignment degree decreases significantly.

Impression creep of a flat-ended cylindrical punch pushed into a viscous layer overlaid on a rigid substrate is analyzed. The method developed here permits us to relate the impression velocity to the punching stress in terms of an auxiliary function, which represents the solution of a set of Fredholm integral equations with a continuous symmetrical kernel. By a series of numerical analysis, the influence of the boundary conditions and the effect of the thickness of the layer on the impression velocity are obtained. For infinite thickness (i.e., h/a →∞, where h is the thickness of the layer and a is the radius of the punch), the impression creep is independent of the stick or slip boundary condition at the indenter/layer interface. For finite thickness such as h/a = 20, the boundary conditions have about 5% effect on the impression velocity. For a thin film, the impressing velocity is very sensitive to the boundary conditions. In fact it suggests a possible experimental way to detect debonding at the interface between the thin film and the substrate.

The topological transformation of grains in three-dimensional normal grain growth was analyzed by Brakke's Surface Evolver method that simulated the boundary motion by curvature. The statistics on elemental processes, which change the number of faces f of a grain, were determined from the simulation. The distribution function of the number of faces P( f ) in a steady structure could be predicted from the difference in the current of grains arriving at and leaving from state f. For the disappearance of one grain, face-creation switching occurred 3.7 times and face-elimination switching occurred 13.2 times on the average.

Adhesion and subcritical debonding at interfaces between a silica-filled epoxy underfill and a silicon die passivated by silicon nitride and benzocyclobutene (BCB) layers were investigated. Adhesion was measured in terms of a critical value of the applied strain energy release rate, G (J/m2 ). Subcritical debond-growth rates in the range of 10−9 to 10−3 m/s were characterized as a function of applied G. Adhesion and subcritical debonding were affected by changes in interfacial chemistry and environment. The surprisingly large effect of adjacent layer elastic properties on interfacial adhesion was demonstrated with simulations of interfacial fracture using a mechanics of materials approach. Interfacial chemistry was modified by using different adhesion promoters, by varying the BCB cure state, and by using different epoxy underfill resins. The effects of environmental variables were studied with temperature- and humidity-controlled environments in order to determine the separate roles of moisture activity and temperature.

Controlled crystallization of BaF2 under two different kinds of monolayers, octadecylamine [CH3(CH2)17NH2] and hexadecanol [CH3(CH2)14CH2OH], has been studied by using x-ray diffraction (XRD) and scanning electron microscope. It was found that the monolayer headgroup, the degree of ionization of the headgroup, etc., had a complicated effect on the selectivity of monolayers for crystal and on the morphology and orientation of crystals grown under the compressed monolayers. At pH = 7.0, XRD analysis showed that (100)-oriented BaF2 crystals were formed under the octadecylamine monolayer, while several kinds of crystals were found under the hexadecanol monolayer. In comparison, at pH = 8.5, both (100)-oriented BaF2 and (111)-oriented Ba(NO3)2 crystals were obtained under the monolayer of octadecylamine. However, crystals formed under hexadecanol monolayer consist of BaF2, Ba(NO3)2, etc. The detailed mechanism for crystallization was discussed in terms of the specific interaction and lattice matching between the monolayer headgroup and the nucleating species.

Single-crystal thulium phosphide (TmP) was grown heteroepitaxially on (001) GaAs substrates by molecular beam epitaxy with the orientation relationship [100]TmP//[100]GaAs and {001}TmP//{001}GaAs. The crystal properties and the defects in TmP/GaAs, GaAs/TmP/GaAs heterostructure were characterized through x-ray diffraction, atomic force microscopy, and transmission electron microscopy. TmP was found to have a huge difference in thermal expansion coefficient compared GaAs, which produced high tensile residual stress and may result in the formation of defects. The major defects in the top GaAs layer are stacking faults or microtwins, and they directly correlated with the islandlike surface morphology of the GaAs overlayer. The composition profiles of the TmP/GaAs heterostructure were measured by secondary ion mass spectrometry. The reason for surface segregation of Tm and Ga atoms is discussed and is primarily due to their higher diffusion coefficient near the surface as compared to that in the TmP epilayer bulk. The thermally stable characters of the TmP/GaAs heterostructures allow them to be promising candidates in various device applications.

The sintering behavior and microwave dielectric properties of (1 − x)Cu3Nb2O8−xZn3Nb2O8 have been investigated using dilatometry, x-ray diffraction, and a network analyzer. It was found that (1 − x)Cu3Nb2O8−xZn3Nb2O8 ceramics have a much lower melting temperature than Zn3Nb2O8 ceramics without Cu3Nb2O8 additives. Samples sintered at 900 °C for 2 h exhibited densities >97% of the theoretical density. Cu3Nb2O8 acts as a sintering aid. Two phase regions were identified with increasing Zn3Nb2O8 contents. A Cu3Nb2O8−Zn3Nb2O8 solid solution exists from 0 < x < 0.5 while a mixture of Cu3Nb2O8 and Zn3Nb2O8 exists from 0.5 < x < 1. The microwave dielectric properties correlated to the crystal structure. In Cu3Nb2O8−Zn3Nb2O8 solid solution region, the variation of dielectric properties could be explained by the structure distortion of Cu3Nb2O8 due to electronic anisotropies of Cu2+ cations.

Samples of an Al–3% Mg alloy and an Al–3% Mg–0.2% Sc alloy were subjected to equal-channel angular pressing (ECAP) to reduce the grain size to approximately 0.2–0.3 μm. Some samples of each alloy were also annealed for 1 h at temperatures of either 423 or 673 K, respectively. High-resolution electron microscopy was used to examine the microstructure both before and after annealing. The grain boundaries after ECAP were wavy and faceted and in high-energy nonequilibrium configurations. These results were consistent with earlier observations of materials subjected to severe plastic deformation using high-pressure torsion. In addition, some grain boundaries in the Al–Mg–Sc alloy had a zigzag appearance after annealing at 673 K, where the straight portions of the boundary were identified as low-energy {111} planes. It is suggested these are mobile boundaries lying in a lowest energy configuration where mobility may be restricted by the presence of incoherent Al3Sc particles.

The degradation behavior of polarization and leakage current characteristics of sol-gel-derived (Pb,La)(Zr,Ti)O3 (PLZT) thin films, with Pt, Ir, and IrO2 top electrodes, by annealing under a 4% H2/96% N2 atmosphere were investigated. The leakage current behaviors of Pt/PLZT/Pt and IrO2/PLZT/Pt capacitors annealed at 300 °C for 20 min in 4% H2 were well consistent with the space-charge-influenced injection model proposed. However, IrO2/PLZT/Pt capacitors recovered at 700 °C for 10 min in Ar ambient after hydrogen anneal were not consistent with the proposed model because a conducting phase of IrPb was formed between the top electrode and PLZT during the recovery anneal at 700 °C in Ar ambient and modified the Schottky barrier height. The true leakage current behavior of IrO2/PLZT/Pt capacitors recovered after hydrogen forming are similar to those of Ir/PLZT/Pt capacitors without the hydrogen-forming gas anneal. The P–E loops of Pt/PLZT/Pt and Ir/PLZT/Pt capacitors showed good recovery through recovery anneal after H2 treatment. However, IrO2/PLZT/Pt capacitors depended on the recovery anneal atmosphere (Ar or O2).

The kinetics and pathways for crystallization of solid, amorphous, yttrium aluminum garnet (YAG) were studied using isothermal differential thermal analysis, x-ray diffraction, and transmission electron microscopy. The activation energy for crystallization was 437 KJ/mol and the measured Avrami exponent was 2.74, which corresponded to three-dimensional crystal growth with a constant number of nuclei. Time–temperature–transformation (T–T–T) curves were developed from the data to predict crystallization rates as a function of temperature. The crystallization pathway for YAG in this system is compared to others reported in the literature.