The present study investigated the effect of passivation on the kinetics of interfacial mass transport by measuring stress relaxation in electroplated Cu films with four different cap layers: SiN, SiC, SiCN, and a Co metal cap. Stress curves measured under thermal cycling showed different behaviors for the unpassivated and passivated Cu films, but were essentially indifferent for the films passivated with different cap layers. On the other hand, stress relaxation measured under an isothermal condition revealed clearly the effect of passivation, indicating that interface diffusion controls the kinetics of stress relaxation. The relaxation rates in the passivated Cu films were found to decrease in the order of SiC, SiCN, SiN, and metal caps. This correlates well with previous studies on the relationship between interfacial adhesion and electromigration. A kinetic model based on coupling of interface and grain-boundary diffusion was used to deduce the interface diffusivities and the corresponding activation energies.

Nano-sized cerium-doped lutetium aluminum garnet (LuAG:Ce) powders were prepared via a sol-gel combustion process from a mixed solution of metal nitrates, using organic glycine as a fuel. The purified crystalline phase of LuAG:Ce was obtained after calcination at 1000 °C for 2 h. The obtained phosphors were agglomerated and had a foamy-like morphology, consisting of pointed crystallites with uniform size of about 40 nm. Both the photoluminescence and the radioluminescence of the calcined powders showed the same two emission bands, corresponding to transitions from the lowest 5d excited state (2D) to the 4f ground state of Ce3+ (2F5/2, 2F7/2). Using the prepared powders, polycrystalline LuAG:Ce optically transparent ceramics were successfully fabricated at 1850 °C for 10 h under vacuum without sintering aids and annealed at 1450 °C for 20 h in air. The sintered ceramics are transparent with an in-line light transmittance in the visible wavelength range of about 50% and have a uniform microstructure with an average grain size of about 8 μm. The radioluminescence of the transparent ceramics is similar to that for calcined powders, except higher in intensity.

Highly (111) textured Pb(Zr0.3Ti0.7)O3 (PZT 30/70) films were deposited on (0001) GaN/sapphire substrates using liquid-source metalorganic chemical vapor deposition (MOCVD) technique at 520 °C and 80 nm/min. The crystallinity of as-deposited PZT films and the structure of PZT/GaN interface were evaluated by x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), respectively. Mitigated by geometric epitaxy and strain energy minimization, the orientation relationships of PZT on epi-GaN, determined using x-ray pole figure and selected area diffraction pattern, were as follows: out-of-plane alignment of [111] PZT//[0001] GaN, and orthogonal in-plane alignments of [112] PZT//[1100] GaN (zone axes) and [110] PZT//[1120] GaN. The nanochemistry of the PZT (150nm)/GaN interface, studied using analytical TEM, indicated a chemically sharp interface with interdiffusion limited to a region below 5 nm. The properties of as-deposited PZT on GaN by MOCVD are briefly compared with PZT by sol-gel processing, radio-frequency sputtering, and pulsed laser deposition.

Highly (100)- and (111)-oriented lead magnesium niobate–lead zirconate titanate (PMN-PZT) films were deposited on Pt(111)/Ti/SiO2/Si substrates using a sol containing polyvinylpyrrolidone (PVP). The molar ratio of Zr/Ti in the PZT was fixed at 60/40, and the PMN content was changed in the range of 0–30 mol%. The films had a dense and columnar microstructure with a thickness of about 1 μm as a result of being spun four times. The crystallographic orientation of the films was controlled by adjusting the pyrolysis temperature; a (100) orientation was obtained by pyrolyzing at 300 °C and a (111) orientation by pyrolyzing at 350 °C. The electrical properties of the films were strongly dependent on the crystallographic orientation and PMN content. With increasing PMN content, the dielectric constant of all of the films increased. On the other hand, the remnant polarization of the (111)-oriented films decreased steadily with increasing PMN content, while that of the (100)-oriented films remained unchanged up to a PMN content of 20%. The piezoelectric coefficients of the (100)-oriented film were consistently higher than those of the (111)-oriented film with the same composition. The highest piezoelectric coefficient was observed for the (100)-oriented film with a composition of 0.2PMN–0.8PZT, indicating the morphotropic phase boundary between the rhombohedral PZT phase and the pseudocubic PMN phase is in the vicinity of this composition.

Binder-free macroscopic single-walled carbon nanotube (SWCNT) solids were prepared by spark plasma sintering (SPS) of purified SWCNTs. The effects of processing temperatures and pressures on the mechanical properties of the SWCNT solids and structural change of SWCNTs in the SWCNT solids were investigated. Transmission electron microscope observation of the SWCNT solids revealed thatthe high-temperature treatment has transformed some part of the SWCNTs into amorphous-like structure and the rest of the SWCNTs remained buried into the above structure. The mechanical properties of the SWCNT solids increased with the increasing processing temperature, probably reflecting the improvement of interfacial strength between SWCNTs and disordered structure of carbon due to the spark plasma generated in the SPS process.

This article reports conversion chemistry of preceramic polymer to ceramic phase during the fabrication of high-temperature stable silicon carbide and silicon carbonitride monolithic porous microchannels. The micromolding in capillariesmethod is used to fabricate porous channels by the initial infiltration of a solution of 1.5-μm diameter silica spheres or 1-μm diameter polystyrene spheres into polydimethylsiloxane channels followed by filling the void space among the spheres by using viscous commercial polymeric precursors. Subsequently, the polymer-sphere composite channel was cured and pyrolysed at 1200 °C under inert atmosphere, and final wet etching step of silica spheres with 10% hydrofluoric acid solution developed the pore structures by removing the silica spheres, whereas polystyrene sphere decomposes at the early stage of pyrolysis.

Surface evolution was studied for strained SrRuO3 films with a nominal 75 nm thickness deposited at various substrate temperatures (650–850 °C). Epitaxial growth of the films was achieved on single TiO2-terminated SrTiO3 (001) substrates by using ion-beam sputtering. The surface morphology of the deposited films was investigated by scanning tunneling microscopy in ambient conditions, and their microstructure was characterized by transmission electron microscopy. The self-organized step-terrace structure was observed for the films deposited at lower than 800 °C, suggesting that the epitaxial growth proceeded by step-flow growth. In particular, each film showed characteristic surface evolutions pertinent to the misfit strain relaxation stage, mostly influenced by the moving segment of misfit dislocations threading up to the surface: surface undulations for the film at the initial stage of relaxation (deposited at 650 °C), circular growth spirals during the relaxation stage (700 °C), and well-ordered step-terrace structure after almost full development of misfit dislocations (750 and 800 °C).

Nanostructured films of TiO2 are becoming more and more attractive as a consequence of their improved sensing properties. Screen printing represents an important low-cost alternative for the production of high-performance devices for the automotive industry. However, to obtain films with superior properties, the composition and each step of the ink production must be carefully controlled. Milling strongly influences the rheological properties of the ink and, as a consequence, the quality of the deposited film. The as-prepared ink was homogenized in a four steps-process with a three-roll mill, and the rheological properties at each intermediate stage were measured. The results showed the dramatic effect of the milling on the flow properties of the nanoink and suggested the importance of a careful control of this step. The rheological behavior of the inks was explained using the basic idea of the transient network theory (TNT) for physically cross-linked networks of polymer solutions. Only an optimized cycle of milling can assure the necessary reproducibility of the ink properties as well as their time stability.

Using geometrically constrained specimens, the plastic flow behaviors of the as-cast and the relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk metallic glass in the dynamic compression were investigated. Both alloys exhibit a significant plasticity in the dynamic compression. The plastic deformation in both alloys is still inhomogeneous, which is characterized by the serrated plastic flow and the formation of shear bands. Free volumes affect the shear banding and the plastic flow. The reduced free volume results in the deviation of the shear banding direction from the maximum shear stress. The relaxed alloy exhibits the obvious stress overshoot, which is consistent with the theoretical prediction using a free volume model.

The creep compliance of viscoelastic materials such as synthetic polymers is an established metric of the rate at which strain increases for a constant applied stress and can, in principle, be implemented at the nanoscale to compare quantitatively bulk or thin film polymers of different structures or processing histories. Here, we outline the evolution of contact creep compliance analysis and application for both conical and spherical indenter geometries. Through systematic experiments on four amorphous (glassy) polymers, two semi-crystalline polymers and two epoxies, we show that assumptions of linear viscoelasticity are not maintained for any of these polymers when creep compliance is measured via conical indentation at the nanoscale, regardless of the rate of stress application (step or ramp). Further, we show that these assumptions can be maintained to evaluate the contact creep compliance Jc(t) of these bulk polymers, regardless of the rate of stress application, provided that the contact strains are reduced sufficiently through spherical indentation. Finally, we consider the structural and physical properties of these polymers in relation to Jc(t), and demonstrate that Jc(t) correlates positively with molecular weight between entanglements or crosslinks of bulk, glassy polymers.

The interfacial reaction between eutectic Sn-9 wt% Zn solder and two different kinds of ball-grid-array substrates (Cu and Au/Ni electroplated Cu) during aging at 150 °C and the shear strength of the resulting joints were investigated. In the Sn-9Zn/Cu joints, only Cu5Zn8 intermetallic compound (IMC) was observed between the solder and Cu layer during the first 100 h of aging. After aging for 1000 h, the layer-type Cu5Zn8 IMC layer was disrupted at the interface, causing it to act as a channel for the diffusion of Sn. As a result, Cu6Sn5 and Cu3Sn IMCs were formed underneath the Cu5Zn8 IMC layer. This interfacial reaction significantly degraded the joint strength. In the case of the Au/Ni/Cu substrate, an AuZn3 IMC layer formed at the interface because of the fast reaction between Au and Zn. In addition, the AuZn3 IMC layer became detached from the interface during reflow. The detachment of the AuZn3 IMC layer is presumably from the mismatch in the coefficients of thermal expansion and weak adhesion between the AuZn3 IMC layer and Ni layer caused by the depletion of the Au layer. When the aging time was extended to 100 h, Ni5Zn21 IMC was observed on the Ni substrate. The shear strength of the aged Sn-9Zn/Au/Ni/Cu joint was significantly related to the detachment of the AuZn3 IMC layer. After aging at 150 °C, fracturing occurred on the detached AuZn3 IMC layer. To ensure the reliability of the Sn-Zn/Au/Ni/Cu joint, the detachment of the AuZn3 IMC needs to be prevented.

The scaling of the piezoelectric and dielectric constants with film thickness in ultra-thin ferroelectric heterostructures is investigated. Epitaxial (001) PbZr0.2Ti0.8O3 films ranging in thickness from 5 nm to 30 nm with top and bottom SrRuO3 electrodes were grown onto (001) SrTiO3 substrates via pulsed laser deposition. Piezoelectric and dielectric measurements were performed using an atomic force microscope. The remnant value of the out of plane piezoresponse (d33) decreases from 60 pm/V for the 30 nm film to just 7 pm/V for the 5 nm film. This systematic decline in d33 is accompanied by a corresponding increase in the coercive field. The d33 loops show a systematic increase in tilt towards the applied field axis as function of reducing thickness coupled with a decrease in piezoelectric tunability. The small-signal relative dielectric response in the direction normal to the film-substrate interface decreases from 140 for a 50 nm film to just 60 for a 8 nm film. A similar drop is also observed in the dielectric tunability, from ∼17% to approximately −2% at an electric field of 750 kV/cm with the film thickness decreasing from 50 nm to 8 nm. We show that these observations cannot be explained using a straightforward application of a modified Landau-Devonshire thermodynamic model that incorporates the internal stresses due to the lattice and thermal expansion mismatch between the film and the substrate. We attribute this behavior to degradation in the polarization due to an intrinsic finite size effect.

The plane-strain bulge test is used to investigate the mechanical behavior of freestanding electroplated Cu thin films as a function of film thickness and microstructure. The stiffness of the films increases slightly with decreasing film thickness because of changes in the crystallographic texture and the elastic anisotropy of Cu. Experimental stiffness values agree well with values derived from single-crystal elastic constants and the appropriate orientation distribution functions. No modulus deficit is observed. The yield stress of the films varies with film thickness and heat treatment as a result of changes in the grain size of the films. The yield stress follows typical Hall-Petch behavior if twins are counted as distinct grains, indicating that twin boundaries are effective barriers to dislocation motion. The Hall-Petch coefficient is in good agreement with values reported for bulk Cu. Film thickness and crystallographic texture have a negligible effect on the yield stress of the films.