Ex) Article Title, Author, Keywords
pISSN 0374-4914
eISSN 2289-0041
pISSN 0374-4914
eISSN 2289-0041
Ex) Article Title, Author, Keywords
Abstract : For the last decade, lead-based organic-inorganic halide perovskite materials have provided fertile ground for studying a large variety of intriguing physical properties and for exploring potential applications to novel optoelectronic devices such as photovoltaics, solar cells, light emitting diodes (LED), photo/X-ray detectors, and photocatalysts. Despite a great deal of previous work from the aspect of fundamental science as well as technological applications, the lead-based halide perovskite materials have been limited due to their vulnerability to ambient conditions such as heat, moisture, and ultraviolet (UV) light. We also note that the lead-based halide perovskites incorporate a toxic lead atom, which is harmful to the human body and the environment. Currently, discovering and developing an alternative material to lead-based halide perovskites are of great interest for eco-friendly and sustainable photovoltaic applications. Oxychalcogenide perovskites are promising candidates for emerging photovoltaic materials and are attracting tremendous attention to the associated optoelectronic fields. In this review paper, we will introduce recent reports on the fascinating characteristics of the oxychalcogenide perovskites and significant efforts to overcome the challenges in their synthesis. While taking a look at the current status of the fabrication of oxychalcogenide thin films, we will discuss a pathway to overcome drawbacks both in realizing epitaxial oxychalcogenide thin films with high crystallinity and in developing next-generation photovoltaic devices with multifunctionality.
Abstract : The light-emitting property of Si micro single crystals was investigated. A Si micro single crystal grown by using the atmospheric-pressure, mixed-source hydride vapor phase epitaxy (HVPE) method has a hexagonal cross-section and has a form of microneedle with an aspect ratio (length/diameter) of 140 or more. Through measurements using field-emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and high-resolution X-ray diffraction (HR-XRD), the grown Si micro crystals were found to be pure single crystals. The electroluminescence (EL) characteristics were investigated by designing a structure of a Si micro single crystal light-emitting device by using a submount substrate. In addition, the cathodoluminescence (CL) and the photoluminescence (PL) were measured and compared to investigate the optical properties. These results are expected to contribute to the application of optoelectronic devices and to the growth of a new Si structure.
Abstract : The effects of partial substitution of nitrate groups at the SO$_{4}$ sites on the superconducting properties of the TlSr$_{4}$Cu$_{2}$O$_{z}$(SO$_{4}$)$_{1-x}$(NO$_{3}$)$_{x}$ system have been investigated. X-ray diffraction data showed that the solubility limit of (NO$_{3}$) was about $x$ = 0.35. The change in the solubility limit of oxyanion for sulfate was discussed in connection with the characteristics of the oxyanion species. Within the solubility limit, the introduction of the nitrate groups did not change significantly the transition temperature of the pristine TlSr$_{4}$Cu$_{2}$O$_{z}$(SO$_{4}$) compound. However, we found that compared to the pristine compound, the introduction of the nitrate groups degraded the stability properties of the sample after annealing at 400$^{\circ}$C in Ar atmosphere.
Abstract : Due to the energy gaps of copper from 2.1 to 2.7 eV, its high light absorption, its nontoxicity and its abundance on the earth, Cu$_{2}$O is an attractive material for use in various areas such as photovoltaic power generation, photocatalytic reactions, water photolysis, nonlinear optics, and gas sensing. Many researches efforts are being conducted to obtain high-quality Cu$_{2}$O thin films. In this study, high-quality, epitaxial Cu$_{2}$O (111) thin films were obtained via a relatively simple method, rapid thermal processes at high temperature of RF sputtered Cu (111) thin film on a sapphire substrate. XRD, SEM and UV-Vis spectroscopy measurements confirmed the high crystallinity of the Cu$_{2}$O (111) thin film oxidized for 30 minutes at a temperature of 800 $^{\circ}$C under an atmosphere of argon with 3 ppm of oxygen. Also, because of the high crystal-quality of the Cu$_{2}$O (111) thin films, blue and indigo energy gaps at room temperature were obtained from the absorption coefficient $\alpha$. The obtained energy band gaps are consistent with the theoretical values obtained from Cu$_{2}$O bulk structures.
Abstract : MAPbX$_3$, is an organic-inorganic perovskite material system which can be applied in various areas such as magneto-optical data storage, solar cells, lasers, LEDs, etc. MAPbI$_3$ and MAPbBr$_3$ are known to undergo a cubic-to-tetragonal transition at temperatures of about 327 K and 220 K and a tetragonal-to-orthorhombic transition at about 150 K and 145 K, respectively. The transmittance spectra of pallet samples are measured in the far-infrared (FIR) region at various temperatures from room temperature to 80 K by using a Fourier transform infrared (FTIR) spectroscopy-type Bruker Vertex 80v spectrometer. The absorption coefficients are obtained and fitted by using the Drude-Lorentz model to obtain other optical constants including the electric permittivity, optical conductivity, and extinction coefficient. Then, the optical conductivity is fitted to obtain the position and damping coefficient of the longitudinal optical (LO) and the transverse optical (TO) phonons for the sample materials, which are used to calculate the electron-phonon coupling constants, polaron mass, and polaron radii.
Abstract : For the last decade, lead-based organic-inorganic halide perovskite materials have provided fertile ground for studying a large variety of intriguing physical properties and for exploring potential applications to novel optoelectronic devices such as photovoltaics, solar cells, light emitting diodes (LED), photo/X-ray detectors, and photocatalysts. Despite a great deal of previous work from the aspect of fundamental science as well as technological applications, the lead-based halide perovskite materials have been limited due to their vulnerability to ambient conditions such as heat, moisture, and ultraviolet (UV) light. We also note that the lead-based halide perovskites incorporate a toxic lead atom, which is harmful to the human body and the environment. Currently, discovering and developing an alternative material to lead-based halide perovskites are of great interest for eco-friendly and sustainable photovoltaic applications. Oxychalcogenide perovskites are promising candidates for emerging photovoltaic materials and are attracting tremendous attention to the associated optoelectronic fields. In this review paper, we will introduce recent reports on the fascinating characteristics of the oxychalcogenide perovskites and significant efforts to overcome the challenges in their synthesis. While taking a look at the current status of the fabrication of oxychalcogenide thin films, we will discuss a pathway to overcome drawbacks both in realizing epitaxial oxychalcogenide thin films with high crystallinity and in developing next-generation photovoltaic devices with multifunctionality.
Abstract : We investigated both the atomic and the electronic structures of poly(3,4-ethylene dioxythiophene) (PEDOT) by performing first-principles calculations and the optical properties by performing experiments. In our first-principles calculation, the use of different exchange-correlation potentials and van der Waals corrections optimize the distance between molecules differently, directly influencing the calculated band gap of PEDOT. In order to experimentally obtain the optical band gap, high-quality semiconducting PEDOT thin films were prepared using vapor-phase polymerization and chemical reduction process. The bandgap of PEDOT was then extracted from the absorption edge in the measured extinction spectrum. Direct comparison between the measured and calculated bandgap shows that the hybrid density functional theory improves the agreement with the experiments.
Abstract : We fabricated a series of Ba0.98SiO3:0.02Eu(2+/3+) phosphors by using a solid-state reaction and precipitation method. We especially studied the effect of SiO2, which is one of the raw materials, on the optical properties such as the excitation and the emission spectra of Eu(3+/2+) ions and the crystallinity of the Ba0.98SiO3:0.02Eu(2+/3+) in samples prepared by using the solid-state reaction method. The Ba0.98SiO3:0.02Eu2+ phosphors fabricated by using the solid-state reaction method showed a maximum emission intensity at 570 nm, which is due to Eu2+, while the sample fabricated using the precipitation method showed emission properties due to both Eu2+ and Eu3+. On the other hand, in the sample in which Li+ was added together with Eu(2+/3+) for charge compensation, the emission intensity due to Eu3+ was increased by 6.6 times, and the emission intensity due to Eu2+ was increased by 1.6 times. Especially, the crystal and the optical properties of BaSiO3:Eu(2+/3+) are slightly differently among researchers, but their origins were partially revealed through this study.
Abstract : The light-emitting property of Si micro single crystals was investigated. A Si micro single crystal grown by using the atmospheric-pressure, mixed-source hydride vapor phase epitaxy (HVPE) method has a hexagonal cross-section and has a form of microneedle with an aspect ratio (length/diameter) of 140 or more. Through measurements using field-emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and high-resolution X-ray diffraction (HR-XRD), the grown Si micro crystals were found to be pure single crystals. The electroluminescence (EL) characteristics were investigated by designing a structure of a Si micro single crystal light-emitting device by using a submount substrate. In addition, the cathodoluminescence (CL) and the photoluminescence (PL) were measured and compared to investigate the optical properties. These results are expected to contribute to the application of optoelectronic devices and to the growth of a new Si structure.
Abstract : Metal-assisted etching (MaE) is one of the most promising etching methods to fabricate silicon nanowires (Si NWs). Here, the effect of noble-metal structure on Si NW fabrication using MaE is investigated. First, two kinds of patterning method are used to fabricate hole arrays in the Au mesh as a catalyst. One is the preparation of the Au mesh by using an anodic aluminum oxide (AAO) disk, and the other is based on the patterning of polystyrene (PS) beads. The Au mesh prepared by using AAO has hole arrays with a smooth edge structure while the other Au mesh patterned by using PS beads shows a rough edge structure of hole arrays. Si NWs are fabricated by using MaE with each different Au mesh. As a result, Si NWs fabricated by using MaE based the AAO disk as a catalyst were found to show a smooth surface that corresponds to the hole structure of the Au mesh. On the other hand, the surface of Si NWs fabricated by using MaE based on PS beads is quite rough with vertically striped structures.
Abstract : The purpose of this study is to evaluate the shielding performance of 3D-printed metal materials against medical radiation. Three-dimensioned printed metal materials such as titanium, zirconium, stainless 316L, molybdenum, palladium, tantalum were selected, and a radiation penetration rate of 5% was observed with tube voltages ranging from 60 kVp to 150 kVp. The consistency was verified by comparing the GATE as a dedicated code with MCNP as a general code based on Monte Carlo simulation. The error rate of each material tended to decrease as the tube voltage was increased. The average error of all materials was confirmed to be 0.55%, given the difference in stochastic statistical fluctuations. Thus data can be used in thickness selection when manufacturing equipment for radiation shielding and as a basis for various future studies.
Abstract : We analyze the elastic scattering cross sections of the K+ + 12C system at 635, 715, and 800 MeV/c, and of the K+ + 40Ca system at 800 MeV/c within the framework of the eikonal model. We found that the calculated results reasonably reproduce the structure of the elastic angular distributions, and provide fairly good agreements with the experimental data over the entire angular range. The elastic differential cross sections of the K+ + 12C system are found to be mainly dominated by the nuclear scattering cross section. The somewhat oscillatory structure observed in the elastic angular distribution of the K+ + 40Ca system can be understood as being due to the effect of interference between the Rutherford and the nuclear scattering amplitudes. We also investigate the critical angular momentum, the strong absorption radius, and the reaction cross section for considered scattering systems.
Abstract : Since the 2009 revised curriculum, modern physics content has been introduced in the Korean secondary curriculum. However, teachers and students have difficulty understanding the modern physics content and it is difficult to find high-tech-contents education research. In this study, we analyzed the principle of a semiconductor and a diode in university textbooks. Specifically, the purpose of this study was to examine the explanations and illustrations concerning the principle of a semiconductor and a diode. Three criteria were established to analyze the content; the description of the semiconductor, the principle of the diode, and the application of the diode. As a result of this study, we found a large difference in the explanations and the illustrations among the textbooks. Especially, some university physics textbooks present the contents concerning the principle of the semiconductor and the diode insufficiently, and essential illustrations to explain the contents were not presented. Based on this study, we suggested several implications.
Abstract : A simple wind tunnel composed of an air circulator and a flow straightner was fabricated. In order to investigate the wind speed characteristics of the manufactured wind tunnel, we measured and analyzed the cross-sectional wind speed with distance. In order to check the wind speed characteristics in each section we divided, the section into 16 regions. We visualized the collected data measured for each cross-section at a distance of 5 cm by using the Origin program. As a result of the analysis, we concluded that the simple wind tunnel device composed only of the air circulator and the flow straightner had relatively uniform wind speed characteristics that depended on the distance. The basic characteristics of the wind tunnel device used in the field of education are identified, and the possibilities of applications in field education are suggested.
Abstract : An optical system with a photogate was developed to measure the speed of a pendulum at the lowest point of motion to obtain the damping and the resistance coefficients of the pendulum. The photogate consisted of a photoresistor, a laser, a mechanical body, and a pendulum ball. A 3D printer was used to produce the mechanical body and pendulum balls of various sizes. Furthermore, an Arduino was used to automate the measurement of the speed at the lowest point of motion and increase the precision. It was found that the resistance coefficient was found to be proportional to the size of the balls, which is regardless of ball mass, consistent with the drag equation for a small Reynolds number. The developed instrument and program were applied to the experiment class, and positive results in education about air resistance was obtained.
Abstract : For Dirac particles such as electrons several quantum mechanical spin operators were proposed in the past, and many studies on the nature of the spin operators were published. On the other hand, spin can be described by using a classical spin 4-vector. In this paper, we investigate the relation between the spin 4-vector and the quantum-mechanical spin operator. For this purpose, we define a spin operator using a spin 4-vector with the consideration that under the Lorentz transformations, positive and negative energy rest states acquire opposite momenta. The resulting spin operator is the same as Foldy- Wouthuysen(FW) spin operator and we conclude that the FW spin operator can be regarded as the quantum-mechanical extension of classical spin 4-vector.
Abstract : Shortcuts to adiabaticity (STA) is a protocol to speed up the quantum adiabatic process through nonadiabatic routes. Time-dependent oscillators, whose specta generate algebra so(2; 1)≈su(1; 1) give quantum invariants and thereby exact quantum states, exhibit a variety of processes from adiabatic to nonadiabatic evolutions. To illustrate how time-dependent oscillators realize the STA, first we use the construction method of an Ermakov-Pinney invariant and find the associated time-dependent oscillator. Then, we introduce a class of time-dependent oscillators whose wave functions are known, and find the condition for the STA for adiabatic and nonadiabatic evolutions.
Abstract : One of the most important applications of XPS (X-ray photoelectron spectroscopy) is to measure the film thickness by using AR-XPS (angle-resolved XPS). The so-called thickogram, which is a nomogram, was developed as an alternative graphical solution to calculate the film thickness easily from the XPS data. It is, however, uncomfortable to photocopy the thickogram and to apply ruler and pencil for finding the graphical intersection. In this research, we developed a computer program with python to automate the thickogram, and published it as an open source on the web so that everyone can access it for the calculation of a film thickness.
Abstract : The one-dimensional variable-mass Dirac equation is connected to various models used throughout many branches of physics. An analog simulation of the equation in a spinor slow light system allows experimental realizations of such models. This work concentrates on an interesting model of historical importance that led to a prediction of charge fractionalization, which in turn occurs due to the presence of a topologically protected zero-energy mode. After describing how the model can be realized in a spinor slow light system, the current work explains how the presence of the zero-energy mode can be verified from the dynamics of the spinor slow light.
Abstract : Spectroscopy characterizes the optical response of a sample to different wavelengths by measuring the transmitted or reflected from the sample surface. Visible spectrometers, which measure the visible light spectrum, are useful in various fields such as chemistry and environmental science for analyzing the absorption and scattering of small particles or molecules in specimens. Portable visible spectrometers allow us to measure the visible spectrum outside the laboratory and to analyze the data through on-site measurements. In this work, we present the design and the implementation of a portable visible spectrometer with Raspberry Pi. We design the integrated control system with Raspberry Pi and implement the system at low cost using energy-efficient hardware and software. By examining the transmission measurement, we demonstrate the reliable performance of our spectrometer compared to conventional UV-Visible spectrometers. We expect this work to be useful for building low-cost and energy-efficient sensor systems such as real-time environmental monitoring devices, for on-site tests.
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
