Ex) Article Title, Author, Keywords
pISSN 0374-4914
eISSN 2289-0041
pISSN 0374-4914
eISSN 2289-0041
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.
Abstract : Ferroelectricity in fluorite-structured oxides such as HfO2 and ZrO2 has attracted increasing interest since the first report in 2011. Despite the history as short as 10 yeas, fabrication tech-nologies have been rapidly developed even for nanoelectronic devices for 20 nm technology node based on characteristic physical scalability. The crystallographic origin of the unexpected ferroelectricity is now accepted as the formation of the Pca21 orthorhombic phase, but the mechanism for the ferroelectric phase formation is still under debate. In thermodynamic theory, the ferroelectric phase is stabilized by various thermodynamic factors, and in the kinetic model, the metastable phase can be formed due to the high kinetic barrier for the formation of a stable phase. In this review, the thermodynamic and kinetic models for the formation of the ferroelectric phase are comprehensively reviewed based on previous studies.
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 Coulomb-modified Glauber model is employed to analyze the experimental data for alpha particle elastic scatterings on $^{116}$Sn and $^{197}$Au at $E_{lab}$ = 240 MeV. We used the surface-matched Gaussian density (SMGD) obtained by matching the Gaussian density profile function to the two-parameter Fermi one for the target nuclei. Calculations with the SMGD are found to reproduce reasonably the structure of the differential cross sections and to give better fits to the elastic data than the calculations without SMGD. The oscillatory behaviors of the elastic angular distributions are found to be related to the strong interference between the near-side and the far-side scattering amplitudes. The inverse potentials calculated with the SMGD provided more closer to the optical model ones in the vicinity of strong absorption radius compared to the potentials calculated without SMGD. We can see that the adoption of the SMGD is useful for obtaining an improved fit to the heavy-nucleus elastic scattering data.
Abstract : In this study, the Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$ phosphor was fabricated using the solid-state reaction method, and its luminescence characteristics were studied. To confirm the crystallinity and the grain size of the Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$ phosphor, an X-ray difraction (XRD) and FE-SEM was measured . The emission spectra of the Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$ phosphor was measured using X-ray and UV light sources. The results comfirmed that the main peaks of Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$:Sm$^{3+}$ and Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$:Dy$^{3+}$ were between 550 to 750 nm and 450 to 800 nm, respectively. Lastly, the decay time was measured and compared to Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$:Sm$^{3+}$ and Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$:Dy$^{3+}$ phosphor. The luminescence spectra result of the X-ray was coincident to UV light sources. The Lu$_{2}$Gd$_{1}$Ga$_{2}$Al$_{3}$O$_{12}$ phosphor is composed of rare earth elements such as Gd$_{2}$O$_{3}$ and Lu$_{2}$O$_{3}$, which have a high effective atomic Z numbers ($Z_{\text{eff}}$ = 55) and high detection efficiency for X-rays and gamma rays. Therefore, phosphar can be applied in fields of medical diagnostic imaging.
Abstract : In this study, the characteristics of infographics presented in the ‘Wave and info-communication’ unit of Physics I textbook according to the 2015 revised curriculum were analyzed. Among the visualization materials presented in the five textbooks, infographics showed a low rate of 17.4%. As a result of an analysis of infographics types, most cases corresponded to the entire range at the composition level. Also, in the analysis of the visual representation elements of infographics, illustration elements were found to be the most. In the analysis according to the expression method, comparative analysis type was the most common, followed by emphasis type, process type, and timeline type. The results of this study suggest that various types of infographic materials that can be used in the physics teaching-learning process need to be developed.
Abstract : In this study, the effect of STEAM programs based on elementary science ’force and motion’ on elementary scientifically gifted students’ perception toward science core competence was examined. To this end, the program was applied to 38 students from two science gifted classes in Jeju City, and the recognition tests on science core competence were conducted before and after the application. The recognition on science core competence was divided into scientific thinking ability, scientific inquiry ability, scientific problem solving ability, scientific communication ability, scientific participation, and lifelong learning ability. As a result of the t-test between the pre and posttests, statistically significant differences were found in all sub-elements of the sciene core competence. These results indicated that this STEAM program had a positive effect on elementary scientifically gifted students’ perception toward science core competence.
Abstract : Materials composed of many nitrogen atoms generally contain much energy, and they have been studied actively in academia and industry, as well as in the fields of defense and aerospace science for the past several decades in order to develop materials with high energy density. A double-sided laser heating system was designed and installed for the first time in the Republic of Korea two years ago in order to synthesize these materials. Using a diamond anvil cell and a laser-heating device to realize extremely high pressure (120 GPa) and temperature (4,500 K) conditions, cubic-gauche nitrogen and CON2 reported in the literature were synthesized for the first time in the Republic of Korea, and they were confirmed by using confocal Raman spectroscopy.
Abstract : We present the results of first-principles calculations for the octahedral tilting structure and the elastic properties of the inorganic halide pervoskite CsPbBr3. The structural optimization was performed for 23 space groups generated by octahedral tilting and in this paper, the low-energy space group is discussed based on the optimized structure. Our calculations not only confirm the experimental findings from high temperature to low temperature structure, but also predict new stable phase of space group number 11. We also correlate the octahedral tilting with the tolerance factor of the halide pervoskite CsPbBr3. In addition, the elastic constants and the elastic properties of the CsPbBr3. structures were calculated. The change in the elastic constant with the space group was analyzed, focusing on how it is related to octahedral tilting.
Abstract : In this paper, a multi-radiotherapy method is proposed, which combine proton therapy with boron neutron capture therapy (BNCT). In this multi-radiotherapy method, BNCT is implemented, firstly, in which, the $^4$He ion and $^7$Li ion are emitted to destroy the local cell with the radiation of thermal neutron, and normally they stop at inside of the local cell due to their short decay ranges. As a result, a large number of $^{7}$L ions are accumulated in the target cell. Then, proton therapy is implemented. Based on the nuclear bombardment reaction $^{7}$Li (p, alpha) $^{4}$He, beside of the dose from the original proton beam, an additional dose contribution might be induced by two alpha particles (each has energy of about 8.7 MeV) emitted for a target cell. For evaluating the new multi-radiotherapy method, are used the Monte Carlo method. Through analyzing the dose distribution of this multi-radiotherapy method and comparising BNCT and proton therapy, we can conclud that under similar distributions of the physical dose, the multi-radiotherapy method may potentially enhance the radiation destruction efficiency for target cells.
Abstract : The changes in the characteristics of the peripheral blood flow rate were analyzed from the waveforms simultaneously measured using a forceps-type pulsimeter equipped with a permanent magnet and hall element and from photoplethysmographs taken before and after treatment by using a personal warmer capable of spinal-centered massage stimulation. Through a linear regression analysis of the measurement data on two test subjects in their 20s who exhibited hypotension and hypertension, respectively, the trend of the central spinal heating effect of the difference before and after treatment was discussed. As a result, the systolic blood pressures of the hypotensive and the hypertensive subjects after hyperthermia were close to normal blood pressure whereas the hypotensive test subject showed a 0.02 m/s increase in peripheral blood flow rate to 0.77 m/s, and the hypertensive test subject showed 0.03 m/s decrease to 0.74 m/s. We hypothesise that spine-centered massage and thermal therapy equipment suitable for use in the digital healthcare field has arrived in the era of the 4th industrial revolution and will be used as an indicator for personal health management.
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 : This study is based on the development of a therapeutic agent using anti-CD3 foralumab monoclonal antibodies which inhibit the overactivation of the T-cells that cause a cytokine storm in the human body. A 7-step process and SiteClick antibody labeling kit was used to bind foralumab antibodies to magnetic nanoparticles through Fc-directed conjugation. The resulting magnetic nanoparticle and antibody composite was compared and analyzed using scanning microscopy, tunneling microscopy, and energy-dispersive spectroscopy. The root-mean-square value of the drift velocity due to Brownian motion of the magnetic nanoparticles (with antibodies attached) in physiological saline, as measured with a nanoparticle tracking analyzer, was 6.98 pix/frame; double that of magnetic nanoparticles without antibodies attached. This was again observed in an animal study when magnetic nanoparticles conjugated to antibodies were injected into the blood vessels of rabbit ears. The antibodies, having a biocompatible functional group attached to their surfaces, showed improved fluidity in bodily fluids.
Abstract : A detector for positron emission tomography (PET) using a small number of photosensors was designed. A light guide was used to obtain a flood image of the scintillation pixel of the designed detector, where the quality of the obtained flood image varies according to the thickness of the light guide. DETECT2000 simulations were performed to calculate the optimal thickness of the light guide to optimize the quality of the flood image. A Gadolinium Aluminium Gallium Garnet (GAGG) scintillator with a size of 2 mm $\times$ 2 mm $\times$ 20 mm was configured in a 10 $\times$ 10 array, and the photosensor consisted of a silicon photomultiplier in a 3 $\times$ 3 array. Light guides were designed with thicknesses from 0.5 mm to 2 mm in 0.5 mm thickness intervals. For quantitative evaluation of the image quality, quantitative values were calculated using the distance between two adjacent scintillation pixel images. The results show that the best flood image was obtained when the detector had a light guide thickness of 1.5 mm. When the PET system was configured using the detector with the optimized light guide thickness presented in this study, the signal processing circuit could be simplified using a small number of photosensors.
Byeong-Hyeon JEONG, Ji-Sang PARK*
New Phys.: Sae Mulli 2020; 70(8): 630-636
https://doi.org/10.3938/NPSM.70.630
Woo Tae Hong, Hyun Kyoung Yang
New Phys.: Sae Mulli 2021; 71(3): 236-241
https://doi.org/10.3938/NPSM.71.236
Hyeong Seon PARK, Seong-Heum PARK, Hyunbok LEE, Heung-Sik KIM*
New Phys.: Sae Mulli 2020; 70(11): 920-927
https://doi.org/10.3938/NPSM.70.920
pISSN 0374-4914
