Ex) Article Title, Author, Keywords
Ex) Article Title, Author, Keywords
Abstract : To investigate the atomic and electronic structures of Si1-xGex and AlxGa1-xN, special quasi-random structures were generated. Before structure optimization, the positions of the constituting atoms were altered to reproduce the bond lengths in Si, Ge, AlN, and GaN as close as possible. The total energy of the optimized structure through the first-principles density functional theory calculation was only 0.03 eV per atom smaller than that of the structure optimization. The lattice constants generally increased as the proportion of Ge or Ga increased. The bond length tended to maintain its value before the mixing of materials, so the change in bond length was smaller than the change in the lattice constants. The band gap of AlxGa1-xN generally increased with the proportion of Al. In the hybrid density functional theory calculation, the band gap increased as the fraction of Hartree-Fock exchange in the functional increased.
Abstract : The Eu3+-doped CaTiO3 (CaTiO3:Eu3+) perovskite phosphorus powders were synthesized using high-energy ball-milling (HEBM). Their crystal structure, surface morphology, and photoluminescence properties were investigated as a function of the europium concentration and annealing temperature. The X-ray diffraction (XRD) peaks of the CaTiO3:Eu3+ powders were good matches with the standard XRD peaks of the orthorhombic CaTiO3 phase without impurities. The field emission scanning electron microscopy (FE-SEM) images of CaTiO3:Eu3+ powders show that the particles increased in size and agglomerated as the annealing temperature increased. The Fourier transform infrared (FT-IR) spectrum confirmed that the absorption bands of CaTiO3:Eu3+ and CaTiO3 were in good agreement, which confirmed that Eu3+ ions were effectively doped into CaTiO3. The highest photoluminescence (PL) emission intensity was observed at an annealing temperature of 1200 °C and a Eu3+ concentration of 6 mol%. The PL spectra showed the strong characteristic peak at 614 nm of the 5D0 → 7F2 electric dipole transition of Eu3+ at an excitation wavelength of 398 nm. These results suggest that the PL emission intensity of CaTiO3:Eu3+ perovskite phosphorus powder can be controlled by Eu3+ concentration and annealing temperature.
Abstract : In this paper, changes in physical properties of MgZnO:In thin films grown on a sapphire substrate using the sol-gel method were investigated as per the concentrations of In and Mg precursors. The properties of the grown thin films were analyzed using XRD, UV-Vis, Hall effect, and XPS. According to the XRD results, all samples showed the c-axis preferential orientation growth. UV-Vis analysis confirmed that the samples exhibited a transmittance of >80% in the visible region. Through the Hall effect measurement, the resistance was found to decrease with the increasing In amount. According to the XPS analysis, when >5 mol% of In was added, the Mg content decreased. The O 1s binding energy was also investigated using XPS, and the bonding state of the thin film was observed by comparing the OI/OII ratio. When >5 mol% of In was added, it interfered with the generation of oxygen vacancy during the synthesis of Mg, thus decreasing the OI/OII ratio.
Abstract : This study examined the features of student-generated drawings to foster their understanding of sound transmission. In this regard, eighteen student-generated drawings constructed by the fifth and sixth elementary science gifted students were collected and analyzed. The students were asked to draw and explain sound transmission between a tuning fork and our ears. The researchers classified the types of student-generated drawings by focusing on `air particles' and `their interactions', which are invisible, and key ideas of sound transmissions, and then analyzed the features of the students' conceptions, as visually expressed in each type. Consequently, most students focused only on the collisions among air particles, the medium transmitting sound, without conceptualizing the particle vibrations, i.e., the back-and-forth movements of particles. For example, some students drew that the particles themselves vibrate, or the particles literally transmit vibrations as if handing over an object. Finally, the educational implications were discussed in terms of alternative conceptions for elementary and middle school students and how to teach sound transmission.
Abstract : We have fabricated copper thin films by using an electroplating method. Specifically, we added an organic additive, Ralufon#14, in the plating electrolyte and observed the variation of the material property of the plated copper caused by Ralufon#14 in the electrolyte. By the addition of Ralufon#14 the crystalline orientation, grain size, and electrical resistivity changed significantly. In addition, compared to the thin films plated with pure electrolyte, the films prepared with Ralufon#14 exhibited considerable increase of the optical reflectance. The changes in crystalline orientation, grain size, and optical reflectance do not show noticeable variation when we increase the concentration of Ralufon#14 in the electrolytes.
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