Flexible strain sensors are recognized as a key component of electronic-skin technology. One of the important features for strain sensors is that they should be able to sensitively recognize the direction of the external stress to accurately detect the various motions of humans or matter. Herein, we successfully developed a directionally responsive piezoresistive strain sensor with asterisk-shaped CNT sensing electrodes to recognize the direction of an applied external stress, thereby overcoming some of the shortcomings of established sensors. Under 5% strain, the change in relative resistance of the sensor developed here differed by up to a factor of 24.5 for different orientations of the sensor electrode relative to the source of the stress, i.e., a high angular dependence of the sensing performance on the external stress direction was observed. In particular, the asterisk-shaped CNT strain sensors showed a super-linear relationship between response and strain for low strains of up to 5%, allowing them to provide a good sensing platform for recognizing micro-deformations. Finally, we demonstrated that our sensor could recognize the direction of the movement of an applied brush and the magnitude and direction of the tilt of a home-built joystick attached onto the sensor device.

In this paper, we describe a method of amorphous silicon carbide film formation for a solar cell passivation layer. The film was deposited on p-type silicon (100) and glass substrates by an RF magnetron co-sputtering system using a Si target and a C target at a room-temperature condition. Several different SiC [Si_1-xC_x] film compositions were achieved by controlling the Si target power with a fixed C target power at 150 W. Then, structural, optical, and electrical properties of the Si_1-xC_x films were studied. The structural properties were investigated by transmission electron microscopy and secondary ion mass spectrometry. The optical properties were achieved by UV-visible spectroscopy and ellipsometry. The performance of Si_1-xC_x passivation was explored by carrier lifetime measurement.

In this study, the phase synthesis and electrochemical properties of A^/A^//A^///B₂O_5+d (A^/: Lanthanide, A^//: Ba, and A^//: Sr) layered perovskites in which Pr and Sm were substituted at the A/-site were investigated for cathode materials of Intermediate Temperature-Operating Solid Oxide Fuel cells (IT-SOFC). In the Pr_xSm_1−xBa_0.5Sr_0.5Co₂O_5+d (x = 0.1–0.9) systems, tetragonal (x < 0.4) and orthorhombic (x ≥ 0.5) crystalline structures were confirmed according to the substitution amount of Pr, which has a relatively large ionic radius, and Sm, which has a small ionic radius. All of the layered perovskite oxide systems utilized in this study presented typical metallic conductivity behavior, with decreasing electrical conductivity as temperature increased. In addition, Pr_0.5Sm_0.5Ba_0.5Sr_0.5Co₂O_5+d (PSBSCO55), showing a tetragonal crystalline structure, had the lowest conductivity values. However, the Area-Specific Resistance (ASR) of PSBSCO55 was found to be 0.10 Ω cm² at 700 °C, which is lower than those of the other compositions.

Carbon nanowall (CNW) and carbon nanotube (CNT) were prepared as anode materials of lithium-ion batteries. To fabricate a lithium-ion battery, copper (Cu) foil was cleaned using an ultrasonic cleaner in a solvent such as trichloroethylene (TCE) and used as a substrate. CNW and CNT were synthesized on Cu foil using plasma-enhanced chemical vapor deposition (PECVD) and water dispersion, respectively. CNW and CNT were used as anode materials for the lithium-ion battery, while lithium hexafluorophosphate (LiPF₆) was used as an electrolyte to fabricate another lithium-ion battery. For the structural analysis of CNW and CNT, field emission scanning electron microscope (FE-SEM) and Raman spectroscopy analysis were performed. The Raman analysis showed that the carbon nanotube in composite material can compensate for the defects of the carbon nanowall. Cyclic voltammetry (CV) was employed for the electrochemical properties of lithium-ion batteries, fabricated by CNW and CNT, respectively. The specific capacity of CNW and CNT were calculated as 62.4 mAh/g and 49.54 mAh/g. The composite material with CNW and CNT having a specific capacity measured at 64.94 mAh/g, delivered the optimal performance.

Carbon nanowalls (CNWs), which are used as electrodes for secondary batteries in energy storage systems (ESSs), have the widest reaction surface area among the carbon-based nanomaterials, but their application is rare due to their low adhesion with substrates. Indium tin oxide (ITO), a representative transparent conducting oxide (TCO) material, is widely used as the electrode for displays, solar cells, etc. Titanium nitride (TiN) is a well-used material as an interlayer for improving the adhesion between two materials. In this study, ITO or TiN thin films were used as an interlayer to improve the adhesion between a CNW and a substrate. The interlayer was deposited on the substrate using a radio frequency (RF) magnetron sputtering system with a four-inch TiN or ITO target. CNWs were grown on the interlayer-coated substrate using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system with a mixture of methane (CH₄) and hydrogen (H₂) gases. The adhesion of the CNW/interlayer/substrate structure was observed through ultrasonic cleaning.