A bismuth telluride alloy-based thermoelectric generator with high-aspect ratio, free-standing legs was fabricated. Such legs are desirable for efficient generator performance from low-grade heat sources but are difficult to assemble because they are fragile and difficult to handle and position. Plunge and wire electro-discharge machining (EDM) were used to produce 150 μm × 300 μm legs, approximately 6-mm long, with high fidelity. Removal of recast material from EDM was necessary for good adhesion of metallization, but sputter etching was found to deteriorate the mechanical strength of the contacts. A wet chemical cleaning process was developed instead that resulted in good adhesion under test conditions. Au was preferred for designs where interconnects could be patterned directly on the module. Module figure of merit (ZT) was 0.72, close to the 0.85 value expected from bulk material property measurements. Impedance spectroscopy and the Harman technique were shown to significantly underestimate module ZT in the present test configuration. Shear and fatigue testing were performed on arrays of high-aspect ratio legs. Legs survived over 104 cycles of shear loading at 90% of the load to failure.

NiMn2−xMgxO4 (0 ≤ x ≤ 0.4) ceramics have been studied by powder x-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis. NiMn2−xMgxO4 ceramics are all single-phase with spinel structure. XRD and IR spectroscopy results indicate that Mg2+ ions occupy A- and B-site of spinel lattice, which inhibits the formation of cation vacancies. Moreover, Mg2+ substitution enhances the tolerance of the oxidation in air. As a result, Mg substitution leads to a significant increase in ρ25, temperature coefficient of resistivity B25/85, and activation energy, which improves the aging property of NiMn2−xMgxO4 negative temperature coefficient thermistors.

Dispersions of reduced tungsten oxide and tungsten bronze nanoparticles are known to show a remarkable absorption of near-infrared (NIR) light applicable to solar control filters for automotive and architectural windows. Origin of the NIR absorption has been investigated by analyzing dielectric constants of CsxWO3 (x = 0.15, 0.25, and 0.33) and WO2.72, and using Mie scattering theory. The optical analysis and Mie scattering theory analysis indicate that a localized surface plasmon resonance and polarons of localized electrons contribute alongside to the observed NIR absorption at different wavelengths.

Transparent conductive oxides (TCOs) are degenerately doped compound semiconductors with wide band gaps (Eg > 3 eV), which are used as transparent electrodes in optoelectronic devices. Reports on the influence of negative ions on the electrical properties of TCO films are reviewed and compared with our results. It was reported that the radial resistivity distributions depend (i) on the excitation mode of the magnetron (direct current or radio frequency), (ii) on the erosion state of the sputtering target, and (iii) on the density of the ceramic targets. This can be explained by the fact that the negative ions in magnetron discharges (in our case O−) are generated at the target surface and accelerated toward the growing films. Their energy and their radial distribution depend on the discharge voltage and the shape of the emitting surface, i.e., of the erosion groove. Ways for reducing the effect of negative ion bombardment are discussed.

High-power impulse magnetron sputtering (HiPIMS) is a promising sputtering-based ionized physical vapor deposition technique and is already making its way to industrial applications. The major difference between HiPIMS and conventional magnetron sputtering processes is the mode of operation. In HiPIMS the power is applied to the magnetron (target) in unipolar pulses at a low duty factor (<10%) and low frequency (<10 kHz) leading to peak target power densities of the order of several kilowatts per square centimeter while keeping the average target power density low enough to avoid magnetron overheating and target melting. These conditions result in the generation of a highly dense plasma discharge, where a large fraction of the sputtered material is ionized and thereby providing new and added means for the synthesis of tailor-made thin films. In this review, the features distinguishing HiPIMS from other deposition methods will be addressed in detail along with how they influence the deposition conditions, such as the plasma parameters and the sputtered material, as well as the resulting thin film properties, such as microstructure, phase formation, and chemical composition. General trends will be established in conjunction to industrially relevant material systems to present this emerging technology to the interested reader.

Laser interference patterning (LIP) and the hereby induced microstructure modifications have been investigated in gold/yttria-stabilized zirconia nanocomposite films. Transmission electron microscopy was used to study the influence of the laser treatment on the structure and microstructure of the samples. The impact of LIP on the friction coefficient has been evidenced. The initial microstructure consisted of gold nanograins homogeneously distributed in the yttria-stabilized zirconia matrix. A noticeable growth and coalescence of gold nanograins occurred near the surface in specific regions. Simultaneously, a foamy morphology, mostly consisting of gold crystals, was formed at the surface and is responsible for a drastic diminution of the friction coefficient after patterning. Furthermore, the influence of the film topography on the friction behavior is analyzed using Abbott–Firestone curves. In contrast to thermal annealing, the laser treatment proposed here is a fast procedure to partially relocate gold at the film surface and provide a local solid lubrication.

Heterogeneous copolymers contain diverse comonomer contents among copolymers, and the extremely diverse case becomes a binary polymer blend. We report a numerical study of crystallization in two series of heterogeneous copolymers that are separated with strong and weak heterogeneities of comonomer distributions, and both of which are composed of crystallizable monomers and noncrystallizable comonomers with various compositions. A comparison of simulation results between these two series of samples demonstrates that, something like a compatibilizer in an incompatible polymer blend, copolymer fractions with intermediate comonomer contents between two compositional extremities depress the prior liquid–liquid demixing on cooling, and hence weaken the subsequent crystallization behaviors. However, we found that in these intermediate fractions, comonomers distribute quite homogeneously on each chain and the amphiphilicity occurs on multiple short sequences, rather than like on a diblock copolymer.

Atomic structures of the Zr48Cu45Al7 as-prepared and annealed metallic glasses (MGs) were investigated by performing the reverse Monte Carlo simulation on the synchrotron radiation-based experiments. It was found that although the annealed sample remains completely amorphous, the volumes of the Al-centered clusters evidently expand, which is attributed to the relatively longer Al–Zr bonds. As a result, the role of Al atoms as the glue atoms to connect and fix the Zr- and Cu-centered large clusters is accordingly weakened, which leads to the ease of the rearrangement of atoms and clusters in the glass state. This study provides an insight into the microstructures of MGs, which extends understanding of the structural evolution in the glass alloys during annealing prior to the precipitation of nanocrystals.

The long afterglow phosphor, CaWO4: Eu3+, is synthesized and the intensity and duration of its afterglow can be enhanced by the Ti4+ and Mg2+ incorporation. The x-ray diffraction patterns depict pure tetragonal CaWO4 of all samples. The emission spectra show the Eu3+ emission and the charge transfer (CT) emission of WO42−. The intensity of CT increases with the Mg2+ incorporation. The excitation spectra monitoring 616 nm exhibit the strongest CT band with Ti4+ incorporation. These results indicate that Mg2+ enhances the efficiency of CT emission of WO42− while the Ti4+ enhances the energy transfer rate from CT to Eu3+. Since the thermoluminescence (TL) curves do not imply a new trap, the enhancement of the afterglow results from the coreinforcement of CT efficiency and energy transfer rate.

Chemical wet etching on c-plane sapphire wafers by three etching solutions (H3PO4, H2SO4, and H3PO4/H2SO4 mixing solution) was studied. Among these etching agents, the mixing H3PO4/H2SO4 solution has the fastest etching rate (1.5 μm/min). Interestingly, we found that H2SO4 does not etch the c-plane sapphire wafer in thickness; instead, a facet pyramidal pattern is formed on the c-plane sapphire wafer. GaN light-emitting diode (LED) epitaxial structure was grown on the sapphire wafer with the pyramidal pattern and the standard flat sapphire wafer. X-ray diffraction and photoluminescence measurement show that the pyramidal pattern on the sapphire wafer improved crystalline quality but augmented the compressive stress level in the GaN LED epilayer. The horizontal LED chips fabricated on the pyramidal-patterned sapphire wafer have a larger light output than the horizontal LED chips fabricated on the standard flat sapphire wafer by 20%.

The (1−x)MgO–xLiF ceramics (x = 0.02–0.08) were successfully sintered when the ceramics were sintered at 950 °C for 4 h in covered crucible. From the crystal structure analysis, it was found that a small amount of Li+ cation occupied Mg2+ site in MgO ceramic; the formation of oxygen vacancy induced by Li substitution for Mg was suggested by the evaluation of the bulk conductivity and the calculation of density of state (DOS) for the (Mg13O43)−60 and (Mg11Li2O42)−58 cluster models. As for the microwave dielectric properties of the (1−x)MgO–xLiF ceramics, the dielectric constant εr and the temperature coefficient of resonant frequency values of the ceramic were independent of the lithium fluoride (LiF) content, and these values were approximately 9.5 and −62 ppm/°C. On the other hand, the quality factor values strongly depended on the LiF content. As a result, the highest value of 282,230 GHz was obtained at x = 0.04. From these results, it is determined that the LiF addition is effective in reducing the sintering temperature of MgO without any detrimental effect on the microwave dielectric properties of MgO ceramics.

Carbon spheres (CSs) with regular shapes (Ø 300–1200 nm) and numerous oxygen groups (–OH, C6H5–C=O, and C=O) were prepared by a simple glucose hydrothermal process. CSs were studied by x-ray powder diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, x-ray photoelectron spectra, and elemental analysis. Their size was directly proportional to temperature and glucose concentration. Their shape could be controlled by temperature and reaction time. To prepare CSs (Ø 300–800 nm) with regular shapes and smooth surfaces, temperature and reaction time in the range of 180–230 °C and 3–4 h, respectively, were optimal. The chemical properties of the CSs were affected by temperature. A phase transformation from amorphous to turbostratic structure took place at T > 230 °C. The number of oxygen groups decreased as the temperature increased, and T ≤ 230 °C were optimal to prepare oxygen-rich CSs. Comparison of oxygen contents and O/C ratios indicated a further carbonization, and the degree was directly related to temperature. A possible formation mechanism for the CSs is proposed.

A range of material systems exist in which nanoscale ionic transport and redox reactions provide the essential mechanisms for memristive switching. One class relies on mobile cations, which are easily created by electrochemical oxidation of the corresponding electrode metal, transported in the insulating layer, and reduced at the inert counterelectrode. These devices are termed electrochemical metallization (ECM) memories, also called conductive bridge random access memories. The memristive characteristics of the ECM cells provide opportunities for circuit design and computational concepts that go beyond those in traditional complementary metal oxide semiconductor (CMOS) technology. Passive memory arrays open up paths toward ultradense and 3D stackable memory and logic gate arrays. Furthermore, the multivalued conductance characteristics allow for potential exploitation of the cells as synapses in neuromorphic circuits in future energy efficient high-performance computer architectures. Despite exciting results obtained in recent years, many challenges have to be met before these physical effects can be turned into competitive industrial technology. Here, we briefly review the basic working principle, the different possible and potential material combinations, and the fundamental electrochemical processes in ECM cells and their implications for device operations. The prospects of ECM-based resistive random access memory as an emerging memory technology are also reviewed in terms of switching speed and scalability.