npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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  • Research Paper 2022-07-31

    Atomic Structure and Electronic Structure of Si1-xGex and AlxGa1-xN: a Density Functional Theory Calculation

    Jeongjun Kim, Youbin Song, Ji-Sang Park*

    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.

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  • Research Paper 2022-07-31

    Optical Properties of CaTiO3: Eu3+ Perovskite Phosphorus Powders on Eu3+ Concentration and Annealing Temperature

    Da Young Kim, Gyeong Bok Jung*

    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 5D07F2 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.

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  • Research Paper 2022-06-30

    A Study on the Changes in the Physical Properties of MgxZn1-xO:In Thin Films Grown Using the Sol-gel Method according to the Precursor Concentration

    Hyo Jin Choi, Min Sang Lee, Hong Seung Kim et al.

    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.

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  • Research Paper 2022-06-30

    An Analysis of Student-generated Drawings in Terms of the Types of Scientific Explanations and Levels of Representations

    Jina Chang, Joonhyeong Park, Jisun Park

    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.

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  • Research Paper 2022-05-31

    Effect of a Suppressing Additive on the Optical Reflectance of Electroplated Copper Surface

    Hoyoung Suh, Mina Heo, Kimin Hong

    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.

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Current Issue

    July, 2022 | Volume 72, No. 7
  • Research Paper 2022-07-31

    Atomic Structure and Electronic Structure of Si1-xGex and AlxGa1-xN: a Density Functional Theory Calculation

    Jeongjun Kim, Youbin Song, Ji-Sang Park*

    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.

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  • Research Paper 2022-07-31

    Minimal Neural Network to Learn the Metal-insulator Transition in the Dynamical Mean-field Theory

    Hyejin Kim*, Dongkyu Kim, Dong-Hee Kim

    Abstract : We present a minimal neural network model to learn classifying the metallic and insulating phases from the real-frequency hybridization function computed in the dynamical mean-field theory for the repulsive Hubbard model at half-filling. The resulting neural network discriminates the phases essentially by reading the presence of the quasiparticle peak. The pattern observed in the weight matrix of neural connectivity allows us to write down a simple form of an indicator that can precisely detect the transition point only with the bath parameters building the Anderson impurity model. The proposed transition indicator is very sensitive to the emergence of zero energy orbital in the quantum bath. We demonstrate the accuracy of the indicator in the discrete bath description with a few orbitals for the exact diagonalization solver.

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  • Research Paper 2022-07-31

    Study of the Electronic Structure for CeAs and CeSb Compounds

    En-Jin Cho, Byung-Hee Choi, Jai-Kwan Jung et al.

    Abstract : The 4f spectra of CeAs and CeSb are measured using 3d-edge resonant photoelectron spectroscopy. The peak at approximately 0.35 eV consists of two components corresponding to a Kondo-related and a non-Kondo-related 4f spectra. Using the bare 4f binding energy of the Kondo-related bulk peak(ϵf(B1)) = 0.58 eV and the average hybridization of the Kondo-related peak(Δav(B1)) = 25.4 meV for CeAs, we obtain a Kondo-related 4f spectrum and find a Kondo temperature of TK = 14 K, a number of 4f electrons nf = 1.0, and a magnetic susceptibility at 0 K of χm(0) = 110 × 10−3 emu/mole. With ϵf(B1) = 0.60 eV and Δav(B1) = 46.3 meV for CeSb, we obtain a Kondo related 4f spectrum and obtain TK = 59 K, nf = 0.97, and χm(0) = 18.8 × 10−3 emu/mole. Considering χm(0)/γ to be constant from the result of Fermi liquid theory, we naturally explain that the specific heat capacity at 0 K (γ) of CeAs has larger values than that of CeSb.

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  • Research Paper 2022-07-31

    Optical Properties of CaTiO3: Eu3+ Perovskite Phosphorus Powders on Eu3+ Concentration and Annealing Temperature

    Da Young Kim, Gyeong Bok Jung*

    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 5D07F2 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.

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  • Research Paper 2022-07-31

    Potential of Visual Basic 6.0 in Teaching and Studying Physics

    Nguyen Ngoc Duy*

    Abstract : Computer programs play an important role in education and studies on subjects in natural science. Using computers, distance teaching and studying physics became easier, especially during the Covid-19 pandemic. Visual Basic 6.0 has emerged among various programming languages as a potential tool for physicists due to its simplicity and interactive graphical interface. This programming language does not require users' extensive computer knowledge or programming skills. With the hope of enhancing the efficiency of teaching and studying physics, I hereby present Visual Basic 6.0 potential to create graphical-user-interface (GUI) computer programs for creating a virtual laboratory, simulations, and numerical calculations. This study is used to enhance the effectiveness of computer programs in teaching, learning and doing research in physics.

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  • Research Paper 2022-07-31

    Discussions on Teaching Methods for Online Physics Experiments

    Jongwon Park, Haktae Kim, Minkyung Kim et al.

    Abstract : This study was conducted to alleviate the difficulty of teaching online physics experiments. To this end, five methods for teaching online physics experiments based on a literature review are summarized: experiments using simulations, experimental videos, remote experiments, experiments focusing on data analysis, and hands-on experiments at home. In this study, the advantages and disadvantages of these five online experimental methods and the conditions for effectively using online physical experiments are summarized. Therefore, the results of this study should be useful for teaching actual online physical experiments. Although this study was initiated because of complete online education caused by COVID-19, online physics learning should continue to expand in ordinary learning situations. Therefore, the results of this study can be meaningfully used even after the COVID-19 pandemic.

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  • Research Paper 2022-07-31

    Feynman Diagrammatic Calculation Technique in Non-relativistic Quantum Mechanical Perturbation Theory

    Won Sik L’Yi*

    Abstract : The Feynman diagrammatic calculation technique, which is widely used for the perturbative calculations in relativistic quantum field theories and quantum many-body theories, is used for time-independent perturbative calculations in non-relativistic one-particle quantum mechanical systems. It is found that Δi, the energy shift of an original state with energy Ei, is determined by a ``propagator'' 1/(Ei−Ej), the potential energy matrix element Vjk, and a kind of non-interactive matrix element −δjkΔi(n), where Δi(n) is the n−th order term of Δi with respect to V. This kind of Feynman diagram technique is quite similar to that of quantum many-body theories, and it helps for understanding the physics behind the perturbative behaviors of various physical systems.

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  • Research Paper 2022-07-31

    Humidity Sensor Based on MoS2-Coated Optical Fiber

    Jong-Ju Moon, Hyeon-Seung Kim, Gwangsik Hong et al.

    Abstract : In this study, a humidity sensor was developed by combining an etched multimode optical fiber with MoS2 nanoparticles. We measured the change in optical properties due to the interaction of MoS2 and H2O molecules. MoS2 was synthesized with Na2MoO4·2H2O and CH3CSNH2 at 200 °C for 24 h. To obtain high sensitivity to humidity, we selected DMF solution as a solvent. Etched optical fiber was downsized to 50 µm, thereby improving the responsivity to humidity. The optical loss of the fiber-optic humidity sensor to human breathing was to 0.5 dB. The response rate was approximately 0.85 s, and the recovery rate was approximately 5.82 s. We confirmed the performance of the sensor for humidity changes from 40 to 80% in a thermo-hygrostat. In addition, we determined that the simultaneous measurement of temperature and humidity is feasible by combining the optical humidity sensor with a fiber Bragg grating.

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  • Research Paper 2022-07-31

    Loading Effect of a Sensor in Measurements of Indirect Laser Stimulation

    Haehyuck Kwon, Seungtae Park, Jong-Rak Park*

    Abstract : We studied the loading effect of a lightweight contact sensor used to measure the displacement of an elastic medium for laser indirect stimulation. The heat transfer and thermoelastic wave equations were numerically solved to simulate the displacement of the elastic medium. We obtained the results for the oscillation frequency and amplitude of the medium vibration for structures with different radii and thicknesses of the medium depending on whether the sensor was attached. When the sensor was attached, both the oscillation frequency and amplitude tended to decrease, and the predicted loading effect on the measurement result was not small.

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Current Issue

July, 2022
Vol.72 No.7

pISSN 0374-4914
eISSN 2289-0041

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pISSN 0374-4914
eISSN 2289-0041