arXiv subjects

Yusaku Magari

Publications and source records attributed to Yusaku Magari.

3 recordsLinked to original sources

arXiv2025

Indium Hydroxide Ceramic Targets: A Breakthrough in High-Mobility Thin-Film Transistor Technology

Thin-film transistors composed of a hydrogen-containing indium oxide active layer are promising candidates for backplane devices in next-generation flat panel displays, offering higher definition and faster operation. However, the hydrogen incorporation process during film deposition poses challenges for scalable and industrial development due to both safety and controllability issues. Here, we demonstrate that using indium hydroxide ceramic as the target material for film deposition overcomes the difficulties associated with hydrogen gas usage. We sintered commercially available indium hydroxide powder using a conventional ceramic process at 150-250°C in air and utilized it for the deposition of hydrogen-incorporated indium oxide films via pulsed laser deposition. The resulting indium oxide films, after thermal annealing, contained a sufficient concentration of hydrogen and exhibited very high electron mobility due to significantly grown grains. Furthermore, we confirmed that the fabricated thin-film transistors exhibited comparably high performance to those produced using the gas-phase hydrogen incorporation method. This approach offers a practical pathway for hydrogen-containing indium oxide-based thin-film transistors in next-generation flat panel displays.

cond-mat.mtrl-sci↗

arXiv2024

Solid-State Electrochemical Thermal Transistors with Large Thermal Conductivity Switching Widths

Thermal transistors that switch the thermal conductivity (\k{appa}) of the active layers are attracting increasing attention as thermal management devices. For electrochemical thermal transistors, several transition metal oxides (TMOs) have been proposed as active layers. After electrochemical redox treatment, the crystal structure of the TMO is modulated, which results in the \k{appa} switching. However, the \k{appa} switching width is still small (< 4 W/mK). In this study, we demonstrate that LaNiOx-based solid-state electrochemical thermal transistors have a \k{appa} switching width of 4.3 W/mK. Fully oxidised LaNiO3 (on state) has a \k{appa} of 6.0 W/mK due to the large contribution of electron thermal conductivity (\k{appa}ele, 3.1 W/mK). In contrast, reduced LaNiO2.72 (off state) has a \k{appa} of 1.7 W/mK because the phonons are scattered by the oxygen vacancies. The LaNiOx-based electrochemical thermal transistor exhibits excellent cyclability of \k{appa} and the crystalline lattice of LaNiOx. This electrochemical thermal transistor may be a promising platform for next-generation devices such as thermal displays.

cond-mat.mtrl-sci↗

arXiv2024

Reliable operation in high-mobility indium oxide thin film transistors

Transparent oxide semiconductors (TOSs) based thin-film transistors (TFTs) that exhibit higher field effect mobility (uFE) are highly required toward the realization of next-generation displays. Among numerous types of TOS-TFTs, In2O3-based TFTs are the front-running candidate because they exhibit the highest uFE ~100 cm2/Vs. However, the device operation of In2O3 TFTs is unreliable; a large voltage shift occurs especially when negative gate bias is applied due to adsorption/desorption of gas molecules. Although passivation of the TFTs is used to overcome such instability, previously proposed passivation materials did not improve the reliability. Here, we show that the In2O3 TFTs passivated with Y2O3 and Er2O3 films are highly reliable and do not show threshold voltage shifts when applying gate bias. We applied positive and negative gate bias to the In2O3 TFTs passivated with various insulating oxides and found that only the In2O3 TFTs passivated with Y2O3 and Er2O3 films did not exhibit threshold voltage shifts. We observed that only the Y2O3 grew heteroepitaxially on the In2O3 crystal. This would be the origin of the high reliability of the In2O3 TFTs passivated with Y2O3 and Er2O3 films. This finding accelerates the development of next-generation displays using high-mobility In2O3 TFTs.

physics.app-ph↗