pISSN 0374-4914 eISSN 2289-0041
• ### Research Paper 2021-08-31

#### Mixed-Source HVPE Method for Growing Single-Crystal Hexagonal Si Microneedles

Gang Seok Lee, Kyoung Hwa Kim, Jung Hyun Park et al.

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.

• ### Research Paper 2021-08-31

#### Recognition of Preservice Physics Teachers’ Self-Understanding and Change Capacity Related to Science Education

Kwanghee Jo, Yong Jae Joung, Heekyong Kim et al.

Abstract : The purpose of this study was to investigate preservice physics teachers’ perceptions of self-understanding and change capacity related to science education. To this end, the responses of 308 students in a department of physics education at 11 universities were analyzed using a questionnaire. The questionnaire was designed to ask for the self-understanding and the change capacity related to science education. The results of the study were as follows. First, preservice physics teachers were positive in their perception of self-understanding as preservice teachers (average 3.81) and as preservice science teachers (average 3.78), the difference between them not being significant. Second, as for the change capacity, they were positive in the recognition of that as general (average 3.97), as preservice teachers (average 3.85), and as preservice science teachers (average 3.83) with significant differences in some factors. By and large, a gender difference was found. These results have great implications for improving preservice physics teachers’ professionalism and their identities as teachers.

• ### Research Paper 2021-07-30

#### Effects of Pr Concentration and Annealing Temperature on the Structural and Optical Properties of Y2O3:Pr3+Nanopowders by High-energy Ball-milling

Gi Pyo CHO, Gyeong Bok JUNG*

Abstract : Pr3+-doped Y2O3 powders were synthesized using high-energy ball milling. Their structural and photoluminescence properties were investigated as functions of the concentration of the praseodymium and the annealing temperatures. The X-ray diffraction peaks of the Y2O3:Pr3+ powders matched the standard X-ray diffraction(XRD) peaks of the cubic Y2O3 phase without impurities well. The intensity of the XRD peak increased with increasing annealing temperature, as did the photoluminescence emission intensity. These results indicate that the crystallinity of the powder improved with increasng annealing temperature. The highest PL emission intensity was observed at an annealing temperature of 1200 ◦C and Pr3+ concentration of 0.1 mol%. The PL spectra showed characteristic peaks at 618 (3P03H6), 630 (2D13H4), 644 (3P03F2), and 509 nm (3P03H5) at an excitation wavelength of 285 nm.

• ### Research Paper 2021-07-30

#### Characterization of Carbon Dots Using HEPA Filter/Fine dust Through the Solvothermal Method

Jong Won CHUNG, Hyun Kyoung YANG*

Abstract : Carbon dots were synthesized using a solvothermal method with a HEPA filter/fine dust as carbon sources. The chemical structure, particle size, surface chemical ligand, electronic structure and luminescent characteristics of the carbon dots were analyzed using transmission electron microscopy. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and photoluminescence measurements, respectively. The photoluminescence spectrum of the carbon dots showed a strong cyan fluorescence around 452 nm under 370 nm excitation. Thus, high-efficiency carbon quantum dots using discarded fine dust can be developed, and the developed quantum carbon dots may be a good candidate for potential applications in the fields of LED color rendering improvement, fingerprint detection and anti-counterfeiting.

• ### Research Paper 2021-06-30

#### Graphene/porous Silicon Solar Cells by Employing Hexagonal Boron Nitride Insulating Film

Seung Gu CHOI, Hye Rin JEON, Dong Hee SHIN*

Abstract : In this research, we successfully fabricated a (trifluoromethanesulfonyl)-amide (TFSA)-doped graphene (TFSA-GR)/porous Si (PSi) solar cell by inserting a chemical vapor deposition-hexagonal boron nitride (h-BN) insulating layer. The photovoltaic parameters of the solar cell depent greatly on the presence or the absence of the h-BN insulating layer and TFSA-GR doping. Specifically, the h-BN insulating layer prevents carrier recombination at the TFSA-GR/PSi interface, thereby improving the charge collection/separation function and, consequently, improving the efficiency. As a result, the TFSA-GR/h-BN/PSi solar cells show a maximum PCE of 12.07%. These results demonstrate that h-BN is excellent as an insulating layer in GR/Si solar cells and is promising for use in graphene/Si-based optoelectronic device application.

## Current Issue

September, 2021 | Volume 71, No. 9
• ### Research Paper 2021-09-30

#### Enhanced Device Performance via Interface Engineering in Polymer-based Optoelectronic Devices

Eui Dae Jung, Myoung Hoon Song*, Yun Seok Nam et al.

Abstract : Achieving efficient electron transport is challenging owing to the large energy barrier between the conduction band of n-type metal oxide and the lowest unoccupied molecular orbital (LUMO) of the emissive layer in inverted polymer light-emitting diodes (PLEDs) or the active layer in inverted polymer solar cells (PSCs), which results in unbalanced charge transport, leading to low device efficiencies. Herein, we have demonstrated that the device performance could be enhanced in both PLEDs and PSCs by treating either the interface between the electron transport layer (ETL) and the emissive layer in PLEDs or the active layers with self-assembled dipole monolayer (SADM), ionic liquid molecules (ILM) and polar solvent (PS). The interface engineering results in a reduction of the energy barrier, which results in enhanced electron transport in both devices. Especially, optimized PLEDs and PSCs show an external quantum efficiency (EQE) of 1.38% and a power conversion efficiency (PCE) of 4.21%, which are enhanced by approximately 138- and 1.37-fold, respectively, compared to the reference devices.

• ### Research Paper 2021-09-30

#### Where does the Energy Flow when Sound Cancels Out? : Proposal for an Experiments to Show Changes in the Energy Supply due to Interaction between Sound Sources

Seokmin Yun, Hyejung Kwak, Hyukjoon Choi*

Abstract : In this study, two sound interference experiments presented in high school textbooks were conducted and checked for changes in the energy supply of sound sources when interference occurs. In general interference situations where the two sources were facing in the same direction, the total energy supplied by the interference did not change. In situations where the two sources faced each other at close distances, the total energy supplied varied with the interference. Furthermore, experiments are conducted using horn speakers and tubes to solve the problems found in experiments where the two sound sources faced each other. When generating normal waves with two opposing sound sources by using horn speakers and tubes, the difference in energy supply was observed to be very large. Afterwards, the experiment was conducted with different experimental conditions. The lower the frequency and the shorter the length of the tube, the greater the difference in energy supplied, and the change in the energy supply was explained through the induction power induced to the speaker. The energy supply was explained using the induced electromotive force generated by using the sound source and was compared to that obtained from the experiment interesting the energy change with frequency.

• ### Research Paper 2021-09-30

#### An Exploration of Students’ Conceptual Resource in Learning Heat and Temperature

Abstract : We report the exploration of students’ conceptual resources before and after obtaining a learning sequence on the topics of heat and temperature. This study was conducted in three phases: before instruction, during instruction and after instruction. This study was conducted in MAN 1 Kota Malang, Indonesia. In general, four conceptual resources were activated by the students: namely, 1) students associate insulators with poor conductors of heat, 2) students correlate material characteristics with their perceptions of heat/cold, 3) students associate both phase change and temperature change with the process of heat flow and energy transfer, and 4) students equate temperature and heat. Our data confirmed that conceptual resource activation was highly context-dependent. For example, students thought that conductors were cooler than insulator materials and that conductors were hotter than insulator materials activated in an appropriate context and an inappropriate context. The results of this study can be used in designing the details of learning about temperature and heat the future.

• ### Research Paper 2021-09-30

#### Analysis of Middle School Students’ Conceptual Types of Light Shapes of Light Bulbs Through Aperture

Yiyoung Kim, Jina Kim*, Jihoon Kang

Abstract : This study was designed to investigate middle school students’ knowledge about how light from a bulb passing through a round aperture appears on a screen and to categorize their responses. Students were asked to take a preconception test in which little light bulbs and light bulbs with long filaments were used and to express the reasons for their responses in a figure or text. First, many students (76.6%) answered that the light image would have round shape regardless of the shape of the light source. Second, the students’ responses were classified as either a ‘scientific response type’ that scientifically responded to the image of the light appearing on the screen, a ‘type derived from the aperture shape’ that the light image depended on the shape of the aperture, ‘type derived from light source shape’ that the light image depended on the shape of the light source, or a ’type limited to the aperture edge’ that the light emitted from the bulb was cut off by the border of the apertured and appears on the screen. The results of this study are expected to help teach science concepts by classifying students’ preconceptions about the image of light on a screen often it had passed through an aperture.

• ### Research Paper 2021-09-30

#### Error in Handling Significant Figures in Polar Coordinates in University Physics Textbooks

Chang Uk Jung*

Abstract : “Significant figures” are basic elements of science. The convenient rule-of-thumb in handling significant figures is to meet the top constraint; that is, “the answer you obtain should not be more precise than the numbers you started with.” I previously demonstrated that applying this rule-of-thumb in calculating the areas of squares and the volumes of cubes could easily and widely violate the top constraint of significant figures. In most textbooks dealing with significant figures in a polar coordinate system with rotational symmetry, I recently found a “more significant” error absent in an ordinary rectangular coordinate system. Herein, I suggest a simple prescription in the notation of angles in polar coordinates.

• ### Research Paper 2021-09-30

#### Performance Evaluation of CdTe Based Plastic Scintillator

Su Jung Min, Ha Ra Kang, Byung Chae Lee et al.

Abstract : In this study, a nanomaterial-loaded plastic scintillator that could be used in decommissioning nuclear facilities was developed and its applicability was evaluated. Plastic detectors with low atomic number are mainly used for alpha and beta measurements. However, by adding a CdTe nanomaterial with a high atomic number to the plastic matrix, Such detecture can be used for gamma-ray detection through mechanisms such as improving the interaction rate with photons and reducing the electron loss rate through wavelength shift or band gap control. In this study, to evaluate the performance of a plastic scintillator containing CdTe nanomaterials we compared, the measurement results obtained using a 60Co radioactive source to those obtained using a commercial plastic scintillator. The results showed that the relative efficiency of the CdTe-loaded plastic scintillator for 60Co detection compared to that of a commercial plastic scintillator was 132% on average. In particular, as a result of calculating the count ratio the effect of the CdTe nanomaterial was observed in the Compton energy region of 60Co. Finally, a plastic detection system containing a nanomaterial can contribute to reductions in both the decommissioning costs and worker exposure through quick and rapid measurements at nuclear facilities.

• ### Research Paper 2021-09-30

#### Characteristics of Polarization Due to a Linearly Polarized Wiggler in a Free-electron Laser

Soon-Kwon NAM*, Yun Seong PARK

Abstract : We analyzed the characteristics of polarization due to a linearly polarized wiggler in a free-electron laser(FEL) oscillator and developed a three-dimensional free-electron laser code with a linearly polarized wiggler in a FEL oscillator for a wiggler period of 0.02 m, a wiggler length of 2 m, an electron beam energy of 13.40 MeV, and an electron beam current of 75 A. The total power due to the linearly polarized wiggler in the fundamental and higher-order modes was studied using the developed FEL code. The intensities of the radiation field with a linearly polarized wiggler for normalized emittances of 1, 5 and 10 mm$\cdot$mrad were calculated. Moreover, the intensity of radiation field with linearly polarized wiggler for the normalized emittances of 1mm$\cdot$mrad was compared to that of the normal wiggler. The intensity of radiation field due to the linearly polarized wiggler for the wavelength was also calculated by the developed code.

• ### Research Paper 2021-09-30

#### Output Optimization of a Q-switched Composite YAG/Yb:YAG/Cr:YAG laser

Youngin PARK, Seongsu KIM, Sungtae PARK et al.

Abstract : We investigated the optimal parameters of a Q-switched, a composite YAG/Yb:YAG/Cr:YAG laser. In order to design a compact and robust Q-switched Yb:YAG laser, a composite YAG/Yb:YAG/Cr:YAG laser medium fabricated by thermal diffusion bonding was used. The noise term was considered in the rate equation for numerical analysis of the effect of noise magnitude acting as the initial signal of the laser pulse. The optimal laser parameters of a composite YAG/Yb:YAG/Cr:YAG laser were determined through an analysis of a modeled Q-switched laser and the experimental results. The Q-switched laser with laser parameters such as output mirror reflectivity, resonator length, and pump beam size optimised could generate a peak power of 0.63 MW with an output energy of $\sim$1.1 mJ and a pulse duration of $\sim$1.7 ns.

• ### Research Paper 2021-09-30

#### Phase-Conjugate Wave in Disperse Orange 3-Doped Polymer

Yang Wu, Hyo Jin Seo, Sun Il Kim* et al.

Abstract : A phase-conjugate wave was generated by irradiating PMMA (poly methyl methacrylate) doped with DO3 (Disperse Orange 3) via degenerate four-wave mixing. In the non-resonant absorption band, the reflectance was measured to be as high as 1.8% at 633 nm. A refractive index change caused by the angular redistribution led to the generation of a phase-conjugate wave; moreover, a holographic memory effect was superposed to the signal. In the resonance absorption band, a maximum reflectance of 0.03% was measured at 476 nm, and a change in absorption led to the generation of phase-conjugate waves. The polarization direction of the probe light was measured as a sine square function with respect to the polarization direction of the pump light to give the intensity of the phase-conjugate wave, and the angular hole burning effect was confirmed.

• ### Research Paper 2021-09-30

#### Study of the Flow Rate in Blood Vessels by Using a Four-element Windkessel Model

Nam Lyong Kang*

Abstract : The artery system is analyzed using a four-element Windkessel model with the characteristic impedance of the artery added as a fourth element to the three-element Windkessel model. A series solution for the four-element Windkessel model is derived using the Laplace transform method. This study examines how the depth and the position of the dicrotic notch in the flow rate in the artery and peripheral vessels vary with peripheral resistance, arterial compliance, blood inertance, and characteristic impedance, as well as the effects of the aging process, such as a decrease in the arterial compliance, increase in the peripheral resistance, increase in the blood viscosity, and decrease the radius of the artery wall, on the risk factors for hypertension.

## Current Issue

• ### A Numerical Calculation of the Nuclear Spin-Parity and Magnetic Moment Based on the Single-Particle Shell Model

Nguyen Ngoc DUY*, Latsamy XAYAVONG, Nguyen Kim UYEN, Vinh Nguyen Thanh PHAM, Tran Viet NHAM HAO

New Phys.: Sae Mulli 2019; 69(10): 1091-1100
https://doi.org/10.3938/NPSM.69.1091

• ### Calculation of the Stacking Fault Energy by Using the Anisotropic Next-Nearest Neighbor Ising Model

Byeong-Hyeon JEONG, Ji-Sang PARK*

New Phys.: Sae Mulli 2020; 70(8): 630-636
https://doi.org/10.3938/NPSM.70.630

• ### Effect of Synthesis Temperature on Luminescent Properties of Carbon dots Originated from Sucrose

Woo Tae Hong, Hyun Kyoung Yang

New Phys.: Sae Mulli 2021; 71(3): 236-241
https://doi.org/10.3938/NPSM.71.236