We investigated the effect of different thin-film thicknesses (25, 30, and 40 nm) on the electrical performance of solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs). The structural properties of the IZO thin films were investigated by atomic force microscopy (AFM). AFM images revealed that the IZO thin films with thicknesses of 25 and 40 nm exhibit an uneven distribution of grains, which deforms the thin film and degrades the performance of the IZO TFT. Further, the IZO thin film with a thickness of 30 nm exhibits a homogeneous and smooth surface with a low RMS roughness of 1.88 nm. The IZO TFTs with the 30-nm-thick IZO film exhibit excellent results, with a field-effect mobility of 3.0(±0.2) cm²/Vs, high Ion/Ioff ratio of 1.1×10⁷, threshold voltage of 0.4(±0.1) V, and subthreshold swing of 0.7(±0.01) V/dec. The optimization of oxide semiconductor thickness through analysis of the surface morphologies can thus contribute to the development of oxide TFT manufacturing technology.

We report on thin-film transistors based on TiO_x pre-annealed by femtosecond laser pulses. A 30-nm thick TiO_x active channel layer was initially deposited by an ALD system. The TiO_x semiconducting films were annealed by irradiation with a femtosecond laser (power: 3 W/cm²) for 5, 25, and 50s. Atomic force microscopy images revealed that the surface of a TiO_x film without femtosecond laser pre-annealing was relatively rough, while after annealing with femtosecond laser pulses, the surface of the TiO_x films became smooth. With increasing radiation time, the surrounding gas atmosphere could have a larger impact on the TiO_x surface; meanwhile, the thin-film roughness decreased. Thin-film transistors with TiO_x active channels pre-annealed at 50s exhibited good transfer characteristics and an on-to-off current ratio of ~10³.

The effect of NH₃ plasma treatment on device characteristics was confirmed for an optimized thin film transistor of poly-Si formed by ELA. When C-V curve was checked for MIS (metal-insulator-silicon), Dit of NH₃ plasma treated and MIS was 2.7×10¹⁰ cm^-2eV^-1. Also in the TFT device case, it was decreased to the sub-threshold slope of 0.5 V/decade, 1.9 V of threshold voltage and improved in 26 cm²V^-1S^-1 of mobility. Si-N and Si-H bonding reduced dangling bonding to each interface. When gate bias stress was applied, the threshold voltage`s shift value of NH₃ plasma treated device was 0.58 V for 1,000s, 1.14 V for 3,600s, 1.12 V for 7,200s. As we observe from this quality, electrical stability was also improved and NH3 plasma treatment was considered effective for passivation.

We investigated the rewritable operation of a non-volatile memory device composed of Al (top)/TiO₂/ indium-zinc-oxide (IZO)/Al (bottom). The oxygen-deficient IZO layer of the device was spin-coated with 0.1 M indium nitrate hydrate and 0.1 M zinc acetate dehydrate as precursor solutions, and the TiO₂ layer was fabricated by atomic layer deposition. The oxygen vacancies IZO layer of an active component annealed at 400℃ using thermal annealing and it was proven to be in oxygen vacancies and oxygen binding environments with OH species and heavy metal ions investigated by X-ray photoelectron spectroscopy. The device, which operates at low voltages (less than 3.5 V), exhibits non-volatile memory behavior consistent with resistive-switching properties and an ON/OFF ratio of approximately 3.6×10³ at 2.5 V.

We investigated solution-processed indium-zinc oxide (IZO) thin-film transistors (TFTs) by inserting a 2-(4- biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) buffer layer. This buffer layer efficiently tuned the energy level between the semiconducting oxide channel and metal electrode by increasing charge extraction, thereby enhancing the overall device performance: the IZO TFT with embedded PBD layer (thickness: 5 nm; width: 2,000 μm; length: 200 μm) exhibited a field-effect mobility of 1.31 cm²V^-1s^-1, threshold voltage of 0.12 V, subthreshold swing of 0.87 V decade^-1, and on/off current ratio of 9.28×10⁵.

Pb(Mn_1/3Nb_2/3)_0.07(Ni_1/3Nb_2/3)_0.10(Zr_0.5Ti_0.5)_0.83O₃ composition ceramics with high piezoelectric properties were fabricated by the columbite precursor method for ultrasonic generators, and the effects of sintering temperature on microstructure and piezoelectric properties were systematically investigated. It was found that the tetragonality of the ceramics decreased with increase in sintering temperature. Moreover, excellent physical properties such as d₃₃=447 pC/N, ε_r=1,843, k_p=0.641, and Q_m=1,207 were obtained for an ultrasonic generator when the second calcination temperature and sintering temperature were 720℃ and 920℃, respectively.

A unimorph piezoelectric cantilever generator with an interdigitated electrode (IDE) was developed for vibration energy harvester applications driven in the longitudinal mode. Hard lead zirconate titanate (PZT) ceramic with a high Q_m of 1,280 was used as the piezoelectric active material. Ten PZT sheets produced by tape casting were laminated and co-fired with an Ag/Pd IDE at 1,050℃ for 2 h. The approximately 280 μm-thick co-fired PZT laminate with the IDE was attached to a stainless steel substrate with an adhesive epoxy for the fabrication of an IDE unimorph cantilever. Its energy harvesting characteristics were evaluated: an output power of 1.1 μW at 120 Hz across the resistive load of 700 k□ was obtained, corresponding to a normalized power factor of 4.1 μW/(G²·cm³).

Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p^-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol^-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.

TiN (titanium nitride) films were prepared using the RF magnetron sputtering technique. The films were deposited by pure N₂ plasma sputtering. Their mechanical properties, such as nano-indentation hardness, friction coefficient, and surface wettability, have been investigated. X-ray diffraction (XRD) studies revealed that the orientation of TiN_X films changed towards the (111) orientation with decreasing working pressure due to a strong compressive stress during deposition. The strongest TiN (111) orientation was found when the film was deposited at a working pressure of 1 Pa. This film showed the largest hardness (16 GPa) and smallest friction coefficient (0.17) among the studied samples. Moreover, this film was found to be accompanied by a water-repellent surface with water contact angle more than 100°.

Electrical relay in an essential part of smart grids, electrical vehicles, and LED lightning systems. Therefore, studying relay reliability is important. Relays using permanent magnet actuators (PMAs), which are energy efficient, are also in the spotlight. However, most of the permanent magnets used in PMAs have a characteristic wherein the magnetic flux decreases as the temperature increases. When the magnetic flux is reduced, the force acting on the actuator is reduced. Therefore, in this study, we measured the decrease in the relay operating speed with permanent magnet reduction due to temperature rise. In addition, changes in the bouncing phenomena due to magnetic flux reduction were analyzed. As a result, the operating speed of the relay has decreased and the bouncing phenomenon has not significantly changed.

Molybdenum oxide (MoO₃) offers pivotal advantages for high optical transparency and low light reflection. Considering device fabrication, n-type MoO₃ semiconductor can spontaneously establish a junction with p-type Si. Since the energy bandgap of Si is 1.12 eV, a maximum photon wavelength of around 1,100 nm is required to initiate effective photoelectric reaction. However, the utilization of infrared photons is very limited for Si photonics. Hence, to enhance the Si photoelectric devices, we applied the wide energy bandgap MoO₃ (3.7 eV) top-layer onto Si. Using a large-scale production method, a wafer-scale MoO₃ device was fabricated with a highly crystalline structure. The MoO₃/p-Si heterojunction device provides distinct photoresponses for long wavelength photons at 900 nm and 1,100 nm with extremely fast response times: rise time of 65.69 ms and fall time of 71.82 ms. We demonstrate the high-performing MoO₃/p-Si infrared photodetector and provide a design scheme for the extension of Si for the utilization of long-wavelength light.

Transparent film heaters employing silver nanowires (Ag NWs) have attracted increasing attention because of their widespread applications. However, the low thermal resistance of Ag NWs limits the maximum operating temperature of the Ag NW film heater. In this study, Ag NW film heaters with high mechanical and thermal stability were successfully developed. The thermal power-out characteristics of the Ag NW heaters were investigated as a function of the Ag NW density. The results revealed that the prepared flexible Ag NW heater possessed high thermal stability over 190℃ owing to ZnO encapsulation. This indicates that the Ag NW film with excellent thermal stability have remarkably high potential for use as electrodes in film heaters operating at high temperatures.