Ex) Article Title, Author, Keywords
Abstract : Twin boundaries (TBs) are one of the defects that form in most single-crystal growth. Although they are usually considered as one of the grain boundaries (GBs) that satisfy a symmetry operation, the properties and formation mechanism of TBs are very different from those of GBs. In particular, in bulk crystals, TBs are usually analogous to ferroelastic domains. TBs are formed to relieve structurally occurring strain when a phase transitions from a high-temperature phase to a low-temperature phase. They are formed in thin films when two islands with different stacking orders at nucleation meet. At this point, TBs are formed when single-crystal islands meet coherently with a coplanar layer. By contrast, GBs are formed when arbitrarily oriented islands meet incoherently. The effects of TBs and GBs on physical properties are greatly different.
Abstract : In this research, TiO2 nanotube arrays were fabricated by using anodization. The change in alignment due to the change in the diameter of the nanotube bottom in accordance with anodization time was analyzed by using field emission scanning electron microscopy. Individually separated TiO2 was confirmed to have formed in the initial stage of anodization. In this process, the expansion and division of the nanotube proceeded with the prolongation of anodization time. As large-diameter nanotubes divided, the distribution values of the diameters decreased, and the stability degree tended to improve. With the passage of time, when the division of the nanotube had been completed to some extent, the expansion of the nanotube proceeded more predominantly, and the average diameter tended to increase. These findings confirmed that the time of anodization affected the alignment and that the bottom diameter was randomly generated at the beginning. Moreover, during TiO2 nanotube growth, the bottom part not only expanded but also split.
Abstract : P-type oxides using holes as carriers exhibit a relatively low hole mobility due to the deep O 2p level; thus, their potential applications are fewer than those of n-type oxides. Recently, a DFT study has reported that Bi-doped In2O3 forms a new in-gap state near the valence band, thereby lowering the formation energy of the acceptor and enabling the formation of a new p-type oxide through additional doping. In addition, a previous experiment on the Bi-doped In2O3 ceramics revealed the in-gap state. In this study, Bi-doped In2O3 films were grown under various conditions to examine the possibility of optical bandgap modulation. Consequently, from a structural viewpoint, the crystalline size grew as the deposition temperature increased; spectroscopically, two optical absorptions were confirmed. While the larger optical bandgap corresponded to bulk In2O3, the smaller one was associated with a newly formed in-gap state owing to Bi doping. Furthermore, the bandgap energy decreased as the deposition temperature increased. Therefore, the reduced optical bandgap with an increased deposition temperature was related to the reduced quantum size effect.
Abstract : The SrRuO3 electrode can improve the dielectric properties of the perovskite structure. Thus, it is the most suitable electrode material for Dynamic Random-Access Memory (DRAM). This study was conducted to investigate the possibility of the SrRuO3 thin film as a transparent conductive oxide (TCO). In this study, an SrRuO3 thin film was deposited on the glass substrates by the RF magnetron sputtering method at room temperature. To observe the difference in optical and electrical properties as per the thin film thickness, the deposition times were set to 5 and 50 min. As the deposition time increased, the film thickness increased from 5 to 68 nm, the optical transmittance decreased from 80% to 40%, and the resistivity (an electrical property) increased from 1.99 to 26.3 mΩ·cm. Consequently, when the SrRuO3 thin films were deposited on the glass substrates for 5 min, a transmittance of about 80% or more, a band gap of 4.57 eV, and a resistivity of 1.99 mΩ·cm were observed, thus verifying that an SrRuO3 electrode can improve the dielectric properties of perovskite.
Abstract : On the basis of Monte Carlo simulation, a liquid scintillation neutrino detector was used to study the conditions for determining the neutrino directionality. The emission angle of the neutron was calculated using the annihilation position of the positron generated through inverse beta decay, which was caused by the neutrino and the gamma-ray emitted by the neutron that was absorbed by gadolinium. When the neutron emission angle was considered as the neutrino directionality, the neutrino demission angle was linearly dependent on the neutrino incidence angle. Therefore, the calculation method for the emission angle of neutrons is a more critical factor in determining the incidence direction of neutrinos compared with the spatial resolution of the detector.
Woo Tae Hong, Hyun Kyoung Yang
New Phys.: Sae Mulli 2021; 71(3): 236-241
YeonJung PARK, Joonghoe DHO*
New Phys.: Sae Mulli 2021; 71(5): 450-456
Jongwon PARK, Insun LEE*
New Phys.: Sae Mulli 2021; 71(5): 476-489