Hydrogen in oxide systems plays a very important role in determining the major physical characteristics of such systems. In this study, we investigated the effect of hydrogen in oxide host systems for various oxygen environments that acted as amorphous oxide semiconductors. The oxygen environment in the sample was controlled by the oxygen gas partial pressure in the radio-frequency-sputtering process. It was confirmed that the hydrogen introduced by the passivation layer not only acted as a “killer” of oxygen deficiencies but also as the “creator” of the defects depending on the density of oxide states. Even if hydrogen is not injected, its role can change owing to unintentionally injected hydrogen, which leads to conflicting results. We discuss herein the correlation with hydrogen in the oxide semiconductor with excess or lack of oxygen through device simulation and elemental analysis.

We investigate the sign of the interfacial Dzyaloshinskii–Moriya interaction (iDMI) energy density in system with inversion symmetry breaking for amorphous and polycrystalline ferromagnetic layers (CoFeB, Co) sandwiched by two different or the same heavy metals (Pt, Ta). By employing Brillouin light scattering, we observe non-reciprocal spin-wave dispersions which is a fingerprint of iDMI in SiO ₂ /(Pt,Ta)/(CoFeB, Co)/(Pt,Ta) systems. We carefully confirm that the signs of DMI of structurally inverted systems are changed accordingly. Negative iDMI for SiO ₂ /Pt/(CoFeB, Co)/Ta and positive iDMI for SiO ₂ /Ta/(CoFeB, Co)/Pt are observed, and iDMI of the symmetric structures (Pt/CoFeB/Pt and Ta/CoFeB/Ta) are not measureable with our Brillouin light scattering setup due to a negligible iDMI. For amorphous CoFeB, the magnitudes of iDMI are the same within the experimental error regardless the stacking order. For the textured Co, however, the magnitude of iDMI for Pt/Co/Ta is about 30 % larger than Ta/Co/Pt structure.

Al/a-InGaZnO_x/AlO_x/Al devices exhibiting gradual memristive switching, facilitated by oxygen vacancies within the active and interfacial layers, with long current level retentions are potential candidates for neuromorphic computing applications.

We investigate the interfacial Dzyaloshinskii-Moriya interaction (iDMI) and the perpendicular magnetic anisotropy (PMA) in the annealed inversion symmetry breaking structures (Pt/Co (CoFeB)/AlOₓ and Ta/CoFeB/AlOₓ) by Brillouin light scattering. The iDMI energy density of Pt/Co and Pt/CoFeB samples decreases while increasing annealing temperature, but the iDMI energy density of Ta/CoFeB sample slightly increases by increasing annealing temperature. By applying the thermal annealing process, PMA energies slightly increase at the Pt/Co interface; however, Pt/CoFeB, (Ta/CoFeB) structures are dramatically decreased (increased) by the annealing process. The effects of the annealing show complicate variation for iDMI and PMA for each structure; however, we find overall weak correlations between iDMI and PMA despite different materials and annealing process.

Asymmetrical electrical properties induced by local acceptor-like defect states in oxide semiconductor thin-film transistors are investigated. In addition, we report on the origin of asymmetrical transport characteristics depending on the drain voltage level. In particular, we observe that these asymmetrical properties depend strongly on this level. Numerical calculations demonstrate that potential barrier lowering in the local area occurs at the drain electrode's edge.