Ex) Article Title, Author, Keywords
Abstract : Thin films of a chemically exfoliated graphene dispersion in water (GDW) were fabricated using a bar-coating method, and their surface morphology, electronic structure, and electrical properties were investigated. The GDW was mixed with a Triton X-100 (2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol, TX) surfactant to control viscosity and surface tension. Through this, graphene could be uniformly deposited on a polyethylene terephthalate substrate. In addition, the electronic structure of the graphene film was significantly different from that of pure graphene due to the oxidation of graphene and the presence of residual functional groups and TX. This difference in material properties causes the differences in the values of the sheet resistances. These results provide fundamental information that will lead to various applications of GDW.
Abstract : The RRAM device having a vertical structure of an Al-TiO2-ITO substrate was manufactured using TiO2 nanoparticles synthesized using ligand. The insulator of the RRAM device was manufactured by synthesizing Ti precursors containing TiCl4 and solutions such as 2-(Methylamino) pyridine. To identify the characteristics of RRAM according to light irradiation, visible light and ultraviolet wavelength light were exposed to the lower electrode ITO and I-V sweep was performed. For the specimen device used in this experiment, resistance increased in the visible wavelength region and resistance decreased in the ultraviolet wavelength region. Through this, the tendency of resistance switching behavior according to light irradiation was confirmed. In this study, the resistance change characteristics of the device were confirmed by adjusting wavelength, light source power, and illumination time. Because the resistance changes according to each wavelength represents the on-off switching role of the device, the manufactured device could be used for neuromorphic device applications.
Abstract : The Raman properties of a hexagonal Si single-crystal structure were investigated. For a sample with a total length of 3230 µm, 46 positions were selected, and the incident laser power was changed from 0.5 mW to 50 mW in 9 steps. Starting from the root, which is the growth engine, the phase changes in the body and in the tip of the hexagon were analyzed using Raman peaks. The Si-IV polymorph → Si-XII → Si-XIII through a series of processes is converted to the Si-IV phase, and the possibility of its being changed back to the semimetal semiconductor Si-IV → Si-III is explained. In addition, it was confirmed that this phase change was confirmed to result in a very stable hexagonal Si single crystal that did not change over 10000 hours. The results are expected in the future to serve as a starting point for various applications in the field of Si research.
Abstract : In proton radiotherapy, the dosimetry protocol TRS-398 does not provide the beam quality correction factors kQ;Q0 for all areas of the spread out Bragg peak (SOBP). Monte Carlo simulations using the TOPAS simulation toolkit were performed to calculate the beam quality correction factors at various depths of the SOBP to observe any variations. The SOBP of the generated proton beam had a range of 15 cm and a width of 15 cm. The beam quality correction factors kQ;Q0 were calculated not only at the reference depth of 7.5 g/cm2 recommended by TRS-398 but also at depths of 4 g/cm2 and 13 g/cm2. The comparison of the simulation results for the absorbed dose with actual measurements showed a slight difference at the surface above the water phantom, but the width of the SOBP was well matched with a difference of less than 1%. The kQ;Q0 factor calculated at the reference depth of 7.5 g/cm2 was 1.045, which is within the error range of the value of 1.030 provided by the TRS-398 protocol. The kQ;Q0 factors calculated at the depths of 4 g/cm2 and 13 g/cm2 were 1.041 and 1.048, respectively. While all the calculated values were within the error range of the value suggested by TRS-398, the observed increase in the kQ;Q0 factor with increasing depth suggests that a position-dependent beam quality correction factor determined through precise measurements may be required to calculate the correct dose.
Abstract : Single-crystal hexagonal Si microneedles with an aspect ratio (length/diameter) of 195 or more were grown by using a mixed-source HVPE method at atmospheric pressure. The newly designed mixed-source HVPE method at atmospheric pressure generates a precursor gas with a high partial pressure due to the rapid reaction of Si and HCl gas at a high temperature of 1200 ◦C. At the same time, hexagonal Si microneedles are grown due to the formation of a nucleus and a seed caused by the interaction between GaCln, AlCln and SiCln gas, and it is designed as a growth mechanism that is separated from the substrate by free fall according to the grown weight. Scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), high-resolution X-ray diffraction (HR-XRD), and Raman spectra revealed a single crystal and pure hexagonal Si microneedle. As a result, the newly designed atmospheric pressure mixed-source HVPE method is expected to enable mass growth of single-crystal hexagonal Si microneedle.
Byeong-Hyeon JEONG, Ji-Sang PARK*
New Phys.: Sae Mulli 2020; 70(8): 630-636
Woo Tae Hong, Hyun Kyoung Yang
New Phys.: Sae Mulli 2021; 71(3): 236-241
Hyeong Seon PARK, Seong-Heum PARK, Hyunbok LEE, Heung-Sik KIM*
New Phys.: Sae Mulli 2020; 70(11): 920-927