A wurtzite nitrogen-doped MgZnO (MgZnO:N) film was grown by plasma-assisted molecular-beam epitaxy (PAMBE) on c-plane sapphire using radical NO as oxygen source and nitrogen dopant. The as-grown film shows n-type conduction at room temperature, but transforms into p-type conduction after annealed. Photoluminescence (PL) spectrum measured at 80 K is dominated by neutral donor-bound exciton emission (D0X) located at 3.522 eV for the n-type MgZnO:N film, but by neutral acceptor-bound exciton emission (A0X) located at 3.515 eV for the p-type MgZnO:N film. By fitting exciton emission intensity of temperature-dependent PL spectra, the binding energies of the D0X and A0X were estimated to be 32 and 43 meV, respectively. Based on the energy shift of exciton emission, the band gap of the MgZnO:N film is estimated to be 3.613 eV, which is 179 meV larger than that of ZnO. Using the Haynes rule, the acceptor energy level of the MgZnO:N film was evaluated to be about 176 meV above the valence band.

Nanoindentation tests and finite element analysis that considers elastic-mesoplastic deformation for single crystals were used to investigate the mechanical properties of CaF2 under spherical indentation. The goal was to gain a better understanding of microfractures and crystalline anisotropy and their effect on the surface quality of CaF2 during manufacturing. In this analysis, indentations of the three main crystallographic planes (100), (110), and (111) were studied and compared to examine the effects of crystalline anisotropy on the load–displacement curves, surface profiles, contact radius, spherical hardness, stress distributions, and cleavage at two stages, namely at the maximum indentation load and after the load had been removed. Our model results were compared with experimental observation of surface microroughness, subsurface damage, and material removal rate in grinding of CaF2.

A floating catalyst chemical vapor deposition method was developed for the synthesis of quasi-one-dimensional (1D) boron nitride (BN) nanostructures. By carefully tuning the experimental parameters such as growth temperature, floating catalyst concentration, and boron precursor, high quality 1D BN nanostructures including nanotubes, nanobamboos, and nanowires were selectively produced. The microstructures of the obtained 1D BN nanomaterials were characterized, and it was found that the nanostructures are composed of hexagonal BN phase with (002) planes stacking in different manners. A growth mechanism of the BN nanostructures was proposed based on the analysis of their structural characteristics and growth conditions.

The microstructural evolution and interfacial reactions of fluxless-bonded, Au-20wt%Sn/Cu solder joint were investigated during reflow and aging. After reflowing at 310 °C, only one thick and irregularly shaped ζ(Cu) layer was formed at the interface. After the prolonged reflow reaction, the AuCu layer was formed between the ζ(Cu) layer and the Cu substrate. During reflowing, the Cu substrate reacted primarily with the ζ-phase in the solder matrix. The solid-state interfacial reaction was much faster at 250 °C than at 150 °C. After aging at 250 °C for 100 h, thick ζ(Cu), AuCu and AuCu3 IMC layers were formed at the interface. The formation of the AuCu3 intermetallic compound (IMC) was caused by Cu enrichment at the AuCu/Cu layer interface. After aging for 500 h, cracks were observed inside the interfacial AuCu layer. The study results clearly demonstrate the need for an alternative surface finish on Cu, to ensure the high temperature reliability of the Au-20Sn/Cu solder joint.

We report the direct deposition of epitaxial 215-nm-thick vanadium sesquioxide (V2O3) films on a- and c-plane sapphire substrates from powder-pressed V2O3 targets via pulsed-laser deposition (PLD) in an evacuated deposition chamber devoid of O2. The films were characterized using x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS), x-ray absorption fine structure (XAFS) spectroscopy, and atomic force microscopy (AFM). XPS measurements confirmed that the stoichiometry of the powder was conserved in the films. XRD patterns together with XAFS measurements proved that V2O3 was epitaxial on the a-sapphire substrate with epitaxial relation (110)film//(110)substrate, and the results are consistent with the epitaxy on the c-plane substrate as well. The room-temperature resistivities of V2O3 films on a- and c-plane substrates were 1.49 × 10−4 and 3.00 × 10−5 Ω m, respectively. The higher resistivities of the films compared to bulk V2O3 might be attributed to thermal stresses resulting from difference in thermal expansion coefficients (TECs) of the films and the substrates.

Radio frequency (rf) magnetron sputtering is used to deposit Ti0.85Nb0.15O2 and Ti0.8Ta0.2O2 films on glass substrates at substrate temperatures (TS) ranging from ∼250 to 400 °C. The most conducting Nb-doped TiO2 films were deposited at TS = 370 °C, with conductivities of ∼60 S/cm, carrier concentrations of 1.5 × 1021 cm−3 and mobilities <1 cm2/V·s. The conductivity of the films was limited by the mobility, which was more than 10 times lower than the mobility for films deposited epitaxially on SrTiO3. The difference in properties is likely caused by the randomly oriented crystal structure of the films deposited on glass compared with biaxially textured films deposited on SrTiO3. The anatase phase could not be stabilized in the Ta-doped TiO2 films, likely because of the high dopant concentration.

ZnS:Mn2+ phosphors were synthesized by a modified solid-state reaction method. In the synthesis method, a sealed vessel is used, where heat and pressure are simultaneously utilized. The effects of various synthesis conditions such as temperature, Mn concentration, and pressure on the cathodoluminescence (CL) were investigated. Among them, pressure had an effect on CL property as much as others. It was observed that CL intensities of ZnS:Mn2+ phosphors increased with the increase of pressure and the best sample showed higher intensity than that of a commercial one by 180%. X-ray diffraction (XRD) and electron paramagnetic-resonance (EPR) were used to understand the enhancement. No change of XRD patterns was observed but the full width at half-maximum (FWHM) of the most intense cubic (111) peak of ZnS:Mn2+ decreased with the increase of pressure. EPR signal intensity of Mn2+ increased with the increase of pressure. The improved crystallinity and more substitution of Zn2+ with Mn metal were believed to be responsible for the enhancement.

The effect of temperature on grinding-induced texture in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) has been investigated using in situ x-ray diffraction (XRD) with an area detector. In contrast with previous results on electrical poling, mechanically-ground PT and soft PZT materials retain strong ferroelastic textures during thermal cycling, even after excursions to temperatures slightly above the Curie temperature. The relationship between the residual stresses in the surface region, caused by grinding, and those resulting from domain wall motion is elucidated by in situ texture measurements obtained during thermal cycling.

Spherical indents in NiTi shape memory alloys can have reversible depth change: deeper depth in the martensitic phase at low temperature and shallower depth in the austenitic phase at high temperature. This is the indentation-induced two-way shape memory effect. After polishing the indents, two-way reversible surface protrusions can occur on the shape memory alloy surfaces upon heating and cooling. The height of the surface protrusion is about the same as the depth of the reversible indent. Further polishing reduces the height of the surface protrusion, which disappears completely when the polished depth is about the length of the contact radius. By comparing finite element analysis and experimental data, we show that the depth at which a protrusion disappears is close to the 10% strain boundary. This suggests that slip-plasticity is responsible for the observed indentation-induced two-way shape memory effect.

The intent of this work is to investigate thermal stability, microstructure, and electrical properties of thin Hf6Ta2O17 high-k gate dielectrics. X-ray diffraction and transmission electron microscopy analysis reveal that an as-deposited Hf6Ta2O17 film is amorphous with a ∼1-nm interfacial layer. After a 1000 °C anneal, the film is a mixture of orthorhombic-Hf6Ta2O17 and monoclinic HfO2 with a thicker interfacial layer. Uniform Hf and Ta Auger depth profiles are observed for as deposited and annealed films. Secondary ion mass spectrometry (SIMS) analysis shows Hf and Ta profiles are unchanged following the 1000 °C anneal, indicating good thermal stability. There is, however, a clear indication of Si up-diffusion into Hf6Ta2O17, particularly after annealing at 1000 °C. No Hf or Ta is found in the Si substrate. Well-behaved capacitance-voltage curves and low leakage current characteristics were obtained for Mo/ Hf6Ta2O17 capacitors for as-deposited and 1000 °C annealed films. A flatband voltage (Vfb) shift towards negative voltage is observed for the annealed film when compared to the as-deposited film, indicating the presence of more positive charge, or less negative charge. Furthermore, capacitance-voltage stress measurements were performed to study charge trapping behaviors. A smaller Vfb shift is observed for as deposited (<10 mV) versus the 1000 °C annealed (30-40 mV) Hf6Ta2O17, indicating more charge trapping after the high temperature anneal.

The influence of different raw material mixtures on β-sialon (Si6−zAlzOzN8−z, 1 ⩽ z ⩽ 4) formation through mechanical activation coupled combustion synthesis (MA-CS) was investigated in low nitriding atmosphere of 1 MPa without diluent inclusions. The MA-CS performed for the first time on sialon raw materials with milling time of 18 min obtained sialons more than three times as pure as those obtained by CS of mixtures ball milled to 1 h (z = 3). The starting materials containing silicon, aluminum, and alumina (z = 4) after MA-CS had an increment of sialon amounts up to 88 mass%.

A facile solution-based processing route using standard spin-coating deposition techniques has been developed for the production of reliable capacitors based on lead lanthanum zirconate titanate (PLZT) with active areas of ⩾1 mm2 and dielectric layer thicknesses down to 50 nm. With careful control of the dielectric phase development through improved processing, ultrathin capacitors exhibited slim ferroelectric hysteresis loops and dielectric constants of >1000, similar to those of much thicker films. Thus, it has been demonstrated that chemical solution deposition is a viable route to the production of capacitor films which are as thin as 50 nm but are still macroscopically addressable with specific capacitance values >160 nF/mm2.

Instrumented indentation has yielded mixed results when used to measure surface residual stresses in metal films. Relative to metals, many glasses and ceramics have a low modulus-to-yield strength (E/σy) ratio. The advantage of this characteristic for measuring residual stress using instrumented indentation is demonstrated by a series of comparative spherical and conical tip finite element simulations. Two cases are considered: (i) a material with E/σy = 24—similar to glass and (ii) a material with E/σy = 120—similar to metal films. In both cases, compressive residual stress shifts the simulated load–displacement response toward increasing hardness, irrespective of tip geometry. This shift is shown to be entirely due to pile up for the “metal” case, but primarily due to the direct influence of the residual stress for the “glass” case. Hardness changes and load–displacement curve shifts are explained by using the spherical cavity model. Supporting experimental results on stressed glasses are provided.

A new quaternary layered carbide, (ZrC)3[Al3.56Si0.44]C3, has been synthesized and characterized by x-ray powder diffraction and thermopower and electrical conductivity measurements. The crystal structure was successfully determined using direct methods and further refined by the Rietveld method. The crystal is trigonal (space group R3m*, Z = 3) with lattice dimensions a = 0.331389(7), c = 4.90084(7) nm, and V = 0.46610(1) nm3. The final reliability indices calculated from the Rietveld refinement were Rwp = 9.53% (S = 1.70), Rp = 7.22%, RB = 1.81%, and RF = 0.94%. The crystal structure is composed of the NaCl-type [Zr3C4] slabs separated by the Al4C3-type [Al0.89Si0.11C] layers. This material had thermoelectric properties comparable to the layered carbides (ZrC)2[Al3.56Si0.44]C3 (Zr2[Al3.56Si0.44]C5), (ZrC)2Al3C2, and (ZrC)3Al3C2 in the temperature range of 373–1273 K, with the maximal power-factor value of 6.6 × 10−5 W m−1K−2 at 545 K. The two quaternary carbides have been found to form a homologous series with the general formula of (ZrC)n[Al3.56Si0.44]C3 (n = 2 and 3).

Multiaxial deformation of Zr55Al10Ni5Cu30 metallic glass was investigated by instrumented indentation tests with a spherical indenter. Contrary to the elastic–rigid-plastic behavior of bulk metallic glasses (BMGs), indentation pressure showed a significant increase with increasing indentation strain, and it was ascribed to a rapid transition of the plastic constraint factor (PCF). However, it was impossible to measure the PCF values from the indentation pressures in the Zr-based BMG because information on uniaxial flow stress was insufficient due to the limited flow strain of 2.2%. Here we developed a PCF assessment method using a relative residual depth hf/hmax, which was experimentally confirmed by adopting it to spherical indentations of a steel sample having well-known flow properties. Flow properties of the BMG were calculated using the new PCF assessment method, and the effects of the materials pileup and low strain indentations on PCF and flow properties were discussed.

A new bulge testing setup for the measurement of the mechanical properties of thin films is presented. This self-built device can be incorporated in an atomic force microscope (AFM), which allows the recording of topographic images of the observed sample membranes under load conditions. Bulge test experiments on different silicon nitride films are presented and compared to nanoindentation experiments. The measured elastic moduli from nanoindentation and bulge testing are in good agreement. Apart from that, the ability to extract stress–strain data from AFM scans is shown, and the results are compared to standard bulge testing experiments. Imaging of the sample microstructure under load conditions is demonstrated on a thin Cu film.

This paper examines the strain rate sensitivity of the hardness νH in relation to the strain rate sensitivity of the flow stress (νσ) in hard solids when there is friction between the indenter and specimen. Finite element analysis is used to simulate indentation creep of von Mises solids with a range of hardness/modulus ratios (H/E*) and coefficients of friction, μ, for indenter–specimen contact. We find that, although the level of H is affected by friction, the ratio νH/νσ as a function of H/E* remains nearly unchanged. Measurements indicate that νH = 0.015 ± 0.02 for fused silica, from which, based on the present analysis, νσ ≈ 0.022 and from which an activation volume of 0.13 nm3 can be estimated for plastic deformation.

We report the preparation and thermoelectric properties of oriented higher manganese silicide (HMS) with a composition of MnSi1.73 bulk. The grain alignment and densification were achieved by rotating high magnetic field and spark plasma sintering (SPS) techniques, respectively. The easy magnetization axis of MnSi1.73 was found to be c-axis, and the applied magnetic field of 2 T was strong enough to rotate the powder with a mean grain size of 1 μm. The c-axis of grains was oriented when applying the magnetic field, and the degree of orientation was further increased after heat treatment. However, a secondary phase that was mono manganese silicide (MnSi) was observed as a result of oxidation on the surface of synthesized powder. The electrical conductivity of the c-axis oriented specimen along the ab-plane was about 40% larger than that for sample processed only by SPS, while the Seebeck coefficient of oriented and nonoriented specimens showed similar values regardless of existence of the second phase. Consequently, the power factor of the c-axis oriented specimen along the ab-plane was enhanced by about 35% compared to the nonoriented one. The proposed approach is found to be very effective not only in obtaining the oriented materials with nonductility but also in enhancing the thermoelectricity.

Solder pots used in wave soldering are usually made using different kinds of steel. Dissolution and interfacial reactions of the Fe substrate in molten Sn-Pb and Sn-Cu solders are investigated in this study. FeSn2 phase is formed in the Sn-0.7wt%Cu/Fe couples reacted at 250, 400, and 500 °C, as well as in the Sn-37wt%Pb/Fe couples reacted at 250 and 400 °C. The activation energies of formation are 123 and 121 kJ/mol in the Sn-Cu/Fe and Sn-Pb/Fe couples, respectively. FeSn phase is the reaction product in the Sn-37wt%Pb/Fe couples reacted 500 °C. The dissolution rates of Fe in the Sn-0.7wt%Cu melt are much higher than those in-the Sn-37wt%Pb melt. The FeSn2 phase layer in the Sn-Cu/Fe couple is not as dense as that in the Sn-Pb/Fe couple and accounts for the very different dissolution rates. Detachment of the reaction FeSn2 phase into the solder matrix is observed in the Sn-Cu/Fe couples, and is a potential contaminant source in wave soldering.

The growth of a Cu2O layer on Cu nanoparticles at 323–373 K was investigated by transmission electron microscopy to elucidate the influence of voids formed at the Cu/Cu2O interface on the oxidation rate. The thickness of the Cu2O formed on Cu nanoparticles with an initial diameter of 10 to ∼35 nm was measured as a function of oxidation time. During the initial oxidation stage until the oxide film is about 2.5 nm thick, the oxide film on nanoparticles of 10 to ∼35 nm in diameter grows rapidly at an almost consistent rate. After that, however, the growth rate of smaller nanoparticles decreases drastically compared with that of larger ones, suggesting that the voids formed near the Cu/Cu2O interface prevent Cu atoms from diffusing outward, because the volume ratio of voids to inner Cu in the case of smaller nanoparticles is considerably higher than that for larger ones at the same oxidation time.