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Next-generation batteries require high-rate energy storage capabilities owing to the advent of fast charging electrical applications. Energy storage materials that can regulate the capacity even at high current densities must be developed. However, this is challenging owing to the limited ion transport kinetics inherent in thick electrodes. The sluggish ion transport can be mitigated by adopting nanomaterials with high specific surface areas or fabricating electrodes with structural alignment. Nevertheless, the rearrangement of materials in electrodes that facilitate fast charging with external forces and additives does not provide a satisfactory ion transport rate. In this study, for realizing a high-rate anode material, facet-controlled three-dimensional holey graphene is fabricated by transferring laser-induced graphene (LIG) to a copper tape in dry condition. This electrode exhibits a consistent capacity of ~114 mAh g−1 at an increased mass loading of 3 mg cm−2 and a high current density of 20 A g−1, implying that 95% capacity can be charged within 3 min. This exceptionally high rate is attributed to the unique structure of the transferred LIG (three dimensionally aligned macro/meso-porous LIG flakes featuring preferential surface facet directions). This fabrication is compatible with the existing manufacturing process for anode materials and can be applied to other energy materials.

We designed and fabricated a gold (Au)-coated silicon nanowires/graphene (Au–SiNWs/G) hybrid composite as a polymer binder-free anode for rechargeable lithium-ion batteries (LIBs). A large amount of SiNWs for LIB anode materials can be prepared by metal-assisted chemical etching (MaCE) process. The Au–SiNWs/G composite film on current collector was obtained by vacuum filtration using an anodic aluminum oxide (AAO) membrane and hot pressing method. Our experimental results show that the Au–SiNWs/G composite has a stable reversible capacity of about 1520 mA h/g which was maintained for 20 cycles. The Au–SiNWs/G composite anode showed much better cycling performance than SiNWs/polyvinylidene fluoride (PVDF)/Super-P, SiNWs/G composite, and pure SiNWs anodes. The improved electrochemical properties of the Au–SiNWs/G composite anode material is mainly ascribed to the composite׳s porous network structure.

This paper reports the results of a study on the microstructure evolution of sputtered BiSb–Te thermoelectric films during post-annealing and its effects on their electronic transport and thermoelectric properties. Combining X-ray diffraction, transmission electron microscopy, and Raman spectroscopy, we illuminate the fundamental aspects of the microstructure evolution: the as-deposited film was Bi0.5Sb1.5Te3 compound in the Bi2Te3-type phase with a nano-crystalline microstructure and the post-annealing prompted a drastic grain growth. The electrical and thermoelectric properties also closely changed following the trend of the grain growth. The Seebeck coefficient, electron mobility, and thermal conductivity increase while the carrier concentration remains flat. The ZT value escalates systematically with the annealing time increasing, reaching around 0.94 after 12 h annealing.

Using resonance and bulge techniques, the mechanical properties of free standing Si-rich SiN"x membranes were precisely measured to evaluate the effect of deposition conditions on them over a narrow range of particular technological interest. Values of the elastic modulus, the residual stress and the thermal expansion coefficient were obtained. It was found that even small differences in gas composition in low pressure CVD deposition make substantial changes in residual stress and significant but much smaller changes in the elastic modulus.

We have evaluated the effect of wet chemical treatment on the interfacial bonding strength of Cu-to-Cu direct bonding. The oxide on a Cu-deposited wafer can be removed by a solution made of hydrofluoric acid and sulfuric acid (HF/H2SO4) or diluted hydrochloric acid (HCl/H2O), which can also improve the bonding quality of Cu-to-Cu bonds. Two 4-inch Cu-deposited wafers were bonded at 250 degrees C via the thermo-compression method. The interfacial adhesion energy of Cu-to-Cu bonding was quantitatively measured by the four-point bending method. After chemical pretreatment for 30 seconds with HF/H2SO4 and HCl:H2O solutions, the measured interfacial adhesion energies were 4.91 J/m2 and 5.51 J/m2, respectively. Microstructural examination of the Cu bonding interfaces showed that the interfacial bonding quality of Cu-to-Cu bonds improved under proper wet chemical etching conditions. Wafer-level cleaning by wet chemical treatment of the Cu surface was found to be a very effective way to improve the bonding quality of Cu bonds, even at bonding temperatures lower than 300 degrees C.

This study provides a framework for evaluating the drop reliability of solder joints using a high-speed lap-shear test. The test specimens employed here were Sn-37Pb/Cu under bump metallization (UBM) solder joints and were aged for 120h at different temperatures (120, 150, and 170^[email protected]?) to examine the effects of aging. We tested them at different loading speeds in the range of 0.01-500mm/s. A careful analysis of the stress-strain graphs attained from the tests, coupled with characterization of the fracture surfaces, discloses that the fracture mode shifts from ductile to brittle as the loading speed escalates. A map of the fracture mode shows that how readily the mode transition with the loading speed occurs can be directly translated into the drop reliability of the solder joint, disclosing that the drop reliability would deteriorate as the aging temperature increases possibly due to the increased IMC thickness. These results underscore the utility of the experimental methodology adopted in this study to evaluate the drop reliability of solder joints.

This study examined the sensitive effects of composition on the microstructure evolution and thermoelectric properties of sputtered Bi-Te films. Bi-Te films of various Te compositions (49 at.% to 60 at.%) were grown by cosputtering deposition and annealed at 200°C for different durations. We examined the microstructure of the films using x-ray diffraction (XRD) and transmission electron microscopy (TEM), and measured the electronic transport and thermoelectric properties. As the Te composition of the films changed from 49 at.% to 60 at.%, the phase of the as-sputtered film changed from the rhombohedral BiTe-type phase to the metastable rock-salt phase, which eventually transformed to the Bi2Te3-type phase upon annealing, instigating microstructure evolution. This phase transformation profoundly influenced the electrical and thermoelectric properties of the films.

This paper reports the microstructure evolution of Bi-Te thermoelectric films upon post-annealing and its effects on the thermoelectric properties. Bi-Te films with the composition of around 61at.% Te and the thickness of 300nm were deposited onto SiO"2-coated Si substrates by using bismuth and tellurium targets in a radio frequency (RF) magnetron sputtering system. We annealed the films at different temperatures (100, 150 and 200^oC) under N"2 ambient for 8h, and characterized the crystallinity and morphology of the Bi-Te films. Microstructure characterization using X-ray diffraction and scanning electron microscopy disclosed that the post-annealing treatment entailed a drastic microstructural evolution by inducing the development of a strong texture of grains with their c-axis oriented normal to the substrate. In addition, we measured the electrical transport and thermoelectric properties of the films to reveal their close link with the microstructure changes. The electron mobility and Seebeck coefficient increase significantly, leading to a remarkable improvement in the power factor from [email protected]/K^2cm for the as-deposited sample to [email protected]/K^2cm for the 200^oC-annealed sample.

It was studied that FePt-Ta thin films prepared on MgO (100) buffer-layer by DC/RF magnetron co-sputtering have shown better magnetic properties and micro structural improvement. The Ta-doped FePt-Ta films indicate somewhat differences in micro structural ordering and the aspect of grain growth after annealing. With respect to magnetic property, the sample having 30% increased coercivity was obtained after a heat treatment at 700^oC. In particular the addition of Ta (5.5%) enhances the L1"0 ordering of FePt at relatively high temperature (above 500^oC).

Bismuth-telluride-based materials have excellent room-temperature thermoelectric properties. In this study, the composition of Bi-Te thin films deposited by RF-magnetron sputtering was systematically varied across a single wafer. X-ray diffraction, field emission-scanning electron microscopy (FE-SEM, JEOL, JSM-7000F) and energy dispersive X-ray spectroscopy (EDS) were then used to investigate the thermoelectric properties of the Bi-Te films as a function of the Te fraction. The Te content of the films ranged from 38% to 81%, and their microstructure and crystal structure varied depending on the Te content. The Seebeck coefficients of the Bi-Te thin films were in the range -10 to 153@mV/K, and the maximum power factor of the films was 3.7x10^-^4W/K^2m, without post annealing.

The increase of electrical resistance during the strain-controlled bending fatigue of 2 μm-thick inkjet-printed or vacuum deposited metallic films (Cu, Ag) on flexible substrates (BT: Bismaleimide Triazine, PI: Polyimide) was investigated. Electrical resistance increased with an increase in the number of fatigue cycles. The rate of increase in the electrical resistance of inkjet-printed Cu films was lower than that of thermally evaporated films. This phenomenon is attributable to the porous microstructure of inkjet-printed Cu films. The porous structure contains a lot of free volume and a large area of free surface, which can be a sinking site for vacancies formed during the cyclic deformation. It was confirmed that a smaller grain size leads to a lower rate of increase in the electrical resistance, which was ascribed to the easy vacancy annihilation due to a short diffusion length of the vacancy to the grain boundary which is a vacancy sinking site. The rate of increase in the electrical resistance was also influenced by the grain boundary geometry. The lower rate of the evaporated Ag film on a BT substrate was attributed to the crack-like grain boundaries, which were expected to behave like pores.

FeRh/FePt bilayers on MgO (100) substrates were fabricated by rf-magnetron sputtering, and the magnetic properties and microstructures of the bilayers were studied in terms of Ta addition to the storage layer. Compared to undoped FeRh/FePt bilayers, FeRh/FePt-Ta bilayer films showed improved magnetic properties and lower degree of interdiffusion. The FeRh/FePt-Ta bilayers clearly demonstrated the AFM-FM transition. Reduced interdiffusion by Ta segregation along grain boundaries was speculated to be a possible cause for the observed improvement in magnetic properties when fabricated at high temperature.

Quantitative analysis of the interfacial adhesion energy of Cu-Cu thermocompression bonds was performed using the four-point bending method with various wet pretreatment conditions. The evaluated interfacial adhesion energies for 1-μm-thick Cu bonding layers were 0.29 J/m2, 1.28 J/m2, 1.64 J/m2, 1.17 J/m2, and 0.43 J/m2 for different acetic acid pretreatment times of 0 min, 1 min, 5 min, 10 min, and 15 min, respectively. There exists an optimum wet etch time for maximum adhesion strength. The change of surface properties with increasing wet etch time was believed to result in the variation of the interfacial adhesion energy. The decrease in interfacial adhesion energy after 5 min seems to result from a decrease in the plastic dissipation energy during interfacial crack propagation with thinner Cu film thickness caused by overetching.

This paper describes the design of a thermal inchworm device to realize precision in-package positioning. The inchworm actuation mechanism includes two metallic actuators facing each other and a workpiece between them. Electrothermal actuation is used to move the workpiece in the desired direction by inputting electric currents in a particular sequence. Nickel is chosen as the material of the actuators due to its desirable electrical, thermal and mechanical properties and availability in fabrication facilities. ANSYS theoretical modeling shows the proposed design can achieve high actuation resolution (0.1 μm) with large driving force and will provide power-free latching as well. The transient analysis defines the current input sequence needed to move the workpiece. The design has been carried out for specific application to optical fiber alignment but has potential for a wide range of other applications.

This paper investigates the effects of the Sb content (х) on (Bi1−xSbx–2Te3 thermoelectric films with х changing widely from 0 (Sb2Te3) to 1 (Bi2 Te3). First, the XRD analysis discloses that with the Sb content (x) increasing, the phase changed gradually from Bi2Te3 to Sb2Te3 as Sb atoms replaced substitutionally Bi atoms. Further microstructure analysis reveals that an extensive grain growth occurred during post-annealing for the samples with high Sb contents. According to the measurement of electrical and thermoelectric properties, the polarity of the charge carrier and Seebeck coefficient switched n-type to p-type in the range of x = 0.45∼0.63. For the n-type samples, the power factor is highest when x = 0.18 around 46.01 μW/K2 whereas Sb2Te3, for the p-type samples, shows the highest value, 62.48 μW/K2cm.

The magnetic properties and structure of FeRh thin film epitaxially grown onto MgO(001) substrate were studied by MPMS(Magnetic Properties Measure System) and in-situ temperature synchrotron XRD(X-ray Diffraction). The transition temperature of FeRh thin films was around 380K. Both M-T curve and d-spacing changes correspond to each other very closely. Abrupt changes in the lattice constants can be observed from the in-situ analysis. Also, there is the likelihood of existence of a new phase.