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Silver nanowires (AgNWs) have shown remarkable potential as materials for transparent conductive electrodes in next-generation flexible devices because of their excellent physical properties. However, despite this advantage, breakdown occurs when AgNWs are exposed to a high temperature and current flow, which has been a significant obstacle. Therefore, a thorough understanding of the breakdown based on local thermal and electrical analyses is essential for developing new devices for various electronic applications. As it is difficult to measure the local heat dissipation occurring at a nanoscale, the breakdown process has not yet been analyzed in detail through an experimental approach. In this study, the local breakdown process due to Joule heat and concentrated current density was examined using scanning thermal microscopy when current flowed through a AgNW network. The results showed that the nanowire breaks at ∼453 K, which is lower than the previously reported temperature of breakdown that occurred only via environmental heating. In this study, we found that the AgNW network can be broken down at temperatures below ∼500 K because the atomic flux due to the combined effects of Rayleigh instability and electromigration is applied to atoms on the surface when the nanowires operate electrically. This work proposes that electromigration and Rayleigh instability should be considered in the design of AgNW devices.

Three-dimensional (3D) nanofabrication using the directed self-assembly of block copolymers (BCPs) holds great promise for the nanoscale device fabrication and integration into 3D architectures over large areas with high element densities. In this work, a robust platform is developed for building 3D BCP architectures with tailored functionality using 3D micron-scale woodpile structures (WPSs), fabricated by a multiphoton polymerization technique. By completely filling the spaces of the WPSs and using the interactions of the blocks of the BCPs with the struts of the WPS, well-developed 3D nanoscopic morphologies are produced. Metal ion complexation with one block of the copolymer affords a convenient stain to highlight one of the microdomains of the copolymer for electron microscopy studies but also, with the reduction of the complexing salt to the corresponding metal, a simple strategy is shown to produce 3D constructs with nanoscopic domain resolution.

We fabricated fully strained Si0.77Ge0.23epitaxial layers on Si substrates and investigated their strain relaxation behaviors under dry oxidation and the effect of oxidation temperatures and times. After the oxidation process, a Ge-rich layer was formed between the oxide and the remaining Si0.77Ge0.23layer. Using reciprocal space mapping measurements, we confirmed that the strain of the Si0.77Ge0.23layers was efficiently relaxed after oxidation, with a maximum relaxation value of ~ 70% after oxidation at 850 °C for 120 min. The surface of Si0.77Ge0.23layer after strain relaxation by dry oxidation was smoother than a thick Si0.77Ge0.23layer, which achieved a similar strain relaxation value by increasing the film thickness. Additionally, N2 annealing was performed in order to compare its effect on the relaxation compared to dry oxidation and to identify relaxation mechanisms, other than the thermally driven ones, occurring during dry oxidation.

In this study, we investigated the formation of a Si1−xGexfin structure in SiO2trench arrays via an ultra-high-vacuum chemical-vapor deposition (UHV-CVD) selective epitaxial growth (SEG) process. Defect generation and microstructures of Si1−xGexfin structures with different Ge concentrations (x= 0.2, 0.3 and 0.45) were examined. In addition, the strain evolution of a Si1−xGexfin structure was analyzed by using reciprocal space mapping (RSM). An (111) facet was formed from the Si1−xGexepi-layer and SiO2trench wall interface to minimize the interface and the surface energy. The Si1−xGexfin structures were fully relaxed along the direction perpendicular to the trenches regardless of the Ge concentration. On the other hand, the fin structures were fully or partially strained along the direction parallel to the trenches depending on the Ge concentration: fully strained Si0.8Ge0.2and Si0.7Ge0.3, and a Si0.55Ge0.45strain-relaxed buffer. We further confirmed that the strain on the Si1−xGexfin structures remained stable after oxide removal and H2/N2post-annealing.

Abstract

Abstract

We demonstrate the influence of the contact resistance on the electrical properties of aIGZO thinfilm transistors TFTs with ZrO2gate insulator grown by rfmagnetron sputtering at room temperature by adopting various channel widths and lengths. These TFTs have all been processed at room temperature with the same channel WLratio WL  5 but different channel widths 50, 150, 250, and 350 µm. As the channel width increases from 50 to 350 µm, the oncurrent and field effect mobility increase from 0.7 to 1 mA and 19 to 31 cm2V s, respectively. However, the subthreshold swing decreases from 0.37 to 0.19 Vdecade. These results show that the contact resistance strongly affects the device performances and should be considered in these applications.

Cardiac tissues are able to adjust their contractile behavior to adapt to the local mechanical environment. Nonuniformity of the native tissue mechanical properties contributes to the development of heart dysfunctions, yet the current in vitro cardiac tissue models often fail to recapitulate the mechanical nonuniformity. To address this issue, a 3D cardiac microtissue model is developed with engineered mechanical nonuniformity, enabled by 3D‐printed hybrid matrices composed of fibers with different diameters. When escalating the complexity of tissue mechanical environments, cardiac microtissues start to develop maladaptive hypercontractile phenotypes, demonstrated in both contractile motion analysis and force‐power analysis. This novel hybrid system could potentially facilitate the establishment of “pathologically‐inspired” cardiac microtissue models for deeper understanding of heart pathology due to nonuniformity of the tissue mechanical environment. Native heart tissues adjust their function when experiencing nonuniform mechanical environments caused by heart diseases (e.g., partial fibrosis). A 3D cardiac microtissue model under a nonuniform mechanical environment is developed by combining fibers with high or low mechanical resistance. This “pathologically‐inspired” 3D in vitro cardiac microtissue model allows for the probing of the adaptivity of cardiac microtissues to nonuniform tissue mechanical environments.

In article number 1901373by Kevin E. Healy, Zhen Ma, and co‐workers, a “pathologically‐inspired” 3D cardiac microtissue model is established based on human induced pluripotent stem cells and laser‐based 3D printing technology. This engineered in vitro model system can facilitate better understanding of the correlation between cardiac contractile dysfunctions and nonuniform tissue mechanical environments.

Epitaxial Si1[?]x Ge x fin layers with x = 0.50 and 0.63 were selectively grown on trench patterned Si (001) substrates with trench widths of 65 and 90 nm. Using a dry oxidation process for the Si1[?]x Ge x fin layers, the Ge was condensed by up to ca. 90% while anisotropic in-plane strain was induced. To analyze the anisotropic in-plane strain behavior, reciprocal space mapping measurements were performed in the directions parallel and perpendicular to the fins. After the condensation, a compressive strain of ca. 1% was induced in the direction parallel to the fin. We discuss the uniaxial stress factor influencing the anisotropic in-plane strain of the condensed Si1[?]x Ge x fin layer in the two trench patterns.

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In this study, disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H10) were used as Si precursors for the growth of Si1[?] x C x epilayers, and the growth properties of the layers were compared. The use of a higher-order silane significantly increased the growth rates of the Si1[?] x C x epilayers at a processing temperature of 650 degC. In addition, a higher growth rate realized by using a higher-order silane promoted an increase in the substitutional carbon concentration in the Si1[?] x C x epilayers owing to the additional injection of a C-source gas (SiH3CH3) and the incorporation of C atoms into substitutional sites. The differences in growth properties between Si precursors were explained on the basis of reaction mechanisms.

We studied Si1-xGex epitaxial growth in steps. Epitaxial Si1-xGex films were deposited on recessed source/drain structure by ultrahigh vacuum chemical vapor deposition process with different growing steps. Each growing step corresponds from initial stage to over-grown stage. By analyzing microstructures of each step, films depositions and defect generations were investigated. Strain evolution, in addition, was investigated in steps. Nano beam diffraction analysis effectively measured strain generations and distributions in the channel region.