• Applied Microscopy
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• 제45권3호
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• pp.115-118
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• 2015

In this review paper, I'd like to introduce the basics of angle-resolved photoemission spectroscopy (ARPES) and some of my results taken at the Pohang Accelerator Laboratory (PAL), the only synchrotron radiation in South Korea. The results show that ARPES is very useful, in particular, for studying two-dimensional materials. It looks like a microscope in momentum space similar to transmission electron microscope imaging atoms in real space.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2004년도 제26회 학술발표회 초록집
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• pp.62-62
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• 2004

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.114.1-114.1
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• 2014

Copper is considered to be the most promising substrate for the growth of high-quality and large area graphene by chemical vapor deposition (CVD), in particular, on the (111) facet. Because the interactions between graphene and Cu substrates influence the orientation, quality, and properties of the synthesized graphene, we studied the interactions using angle-resolved photoemission spectroscopy. The evolution of both the Shockley surface state of the Cu(111) and the p band of the graphene was measured from the initial stage of CVD growth to the formation of a monolayer. Graphene growth was initiated along the Cu(111) lattice, where the Dirac band crossed the Fermi energy ($E_F$) at the K point without hybridization with the d-band of Cu. Then two rotated domains were additionally grown as the area covered with graphene became wider. The Dirac energy was about 0.4 eV and the energy of the Shockley surface state of Cu(111) shifted toward the $E_F$) by 0.15 eV upon graphene formation. These results indicate weak interactions between graphene and Cu, and that the electron transfer is limited to that between the Shockley surface state of Cu(111) and the p band of graphene. This weak interaction and slight lattice mismatch between graphene and Cu resulted in the growth of rotated graphene domains ($9.6^{\circ}$ and $8.4^{\circ}$), which showed no significant differences in the Dirac band with respect to different orientations. These rotated graphene domains resulted in grain boundaries which would hinder a large-sized single monolayer growth on Cu substrates.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.146.2-146.2
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• 2013

Copper is considered to be the most promising substrate for the growth of high-quality and large area graphene by chemical vapor deposition (CVD), in particular, on the (111) facet. Because the interactions between graphene and Cu substrates influence the orientation, quality, and properties of the synthesized graphene, we studied the interactions using angle-resolved photoemission spectroscopy. The evolution of both the Shockley surface state of the Cu(111) and the ${\pi}$ band of the graphene was measured from the initial stage of CVD growth to the formation of a monolayer. Graphene growth was initiated along the Cu(111) lattice, where the Dirac band crossed the Fermi energy (EF) at the K point without hybridization with the d-band of Cu. Then two rotated domains were additionally grown as the area covered with graphene became wider. The Dirac energy was about -0.4 eV and the energy of the Shockley surface state of Cu(111) shifted toward the EF by ~0.15 eV upon graphene formation. These results indicate weak interactions between graphene and Cu, and the electron transfer is limited to that between the Shockley surface state of Cu(111) and the ${\pi}$ band of graphene. This weak interaction and slight lattice mismatch between graphene and Cu resulted in the growth of rotated graphene domains ($9.6^{\circ}$ and $8.4^{\circ}$), which showed no significant differences in the Dirac band with respect to different orientations. These rotated graphene domains resulted in grain boundaries which would hinder a large-sized single monolayer growth on Cu substrates.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.84.2-84.2
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• 2007

• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2906-2910
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• 2011

A fluorescent nucleoside analogue, $^AC$, featuring two non-complementary nucleobases linked through an ethynyl group, was synthesized. The extended ${\pi}$-conjugation imparts $^AC$ with red-shifted absorbance (relative to adenine and cytosine) and pale-blue fluorescence. It spontaneously forms nanoparticles, which exhibit considerably enhanced fluorescence, without the help of any additional stabilizing agent. The DMSO/water ratio was an important factor influencing the construction of the NPs. X-ray crystallography confirmed the structure of $^AC$; dynamic light scattering and scanning electron microscopy confirmed the existence of the nanoparticles.

• 한국가시화정보학회지
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• 제8권2호
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• pp.45-50
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• 2010

The objective of this study is to elucidate the feasibility of synchrotron X-ray micro CT as a non-destructive imaging method to visualize the three-dimensional morphological structures of biological and non-biological samples. The experiments were conducted in 7B2 X-ray micro CT beamline in Pohang Accelerate Laboratory (PAL). A rotational 3-axis stage was specially designed for $0^{\circ}-180^{\circ}$ scanning of test samples. Preliminary tests were performed for opaque samples including a mosquito head, a plant seed and gas diffusion layer (GDL) of polymer electrolyte fuel cell to verify the feasibility of the X-ray micro CT. It visualized clearly the internal structure of all the test samples, supporting its usefulness.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.153-158
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• 1997

This paper describes a formal safety analysis technique which is demonstrated by performing empirical formal safety analysis with the case study of beamline hutch door Interlock system that is developed by using PLC(Programmable Logic Controller) systems at the Pohang Accelerator Laboratory. In order to perform formal safety analysis, we have built the Z formal specifications representation from user requirement written in ambiguous natural language and target PLC ladder logic, respectively. We have also studied the effective method to express typical PLC timer component by using specific Z formal notation which is supported by temporal history. We present a formal proof technique specifying and verifying that the hazardous states are not introduced into ladder logic in the PLC-based safety critical system.

• 대한화학회지
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• 제61권3호
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• pp.129-131
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• 2017

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.202.2-202.2
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• 2014

We have studied the bonding structures of five membered aromatic ring heterocyclic molecules, such as furan, thiophene, and selenophene, adsorbed on the Si(100) surface at room temperature with density functional theory. Additionally, we have investigated the evolution upon annealing of thiophene and selenophene molecules on the Si(100) surface by the core-level photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS). The core-level-spectra measured at different temperatures are consistently interpreted in terms of various adsorption structures suggested by theoretical calculations. In this study, we found the most suitable structures by theoretical and experimental results considering room temperature and mild thermal annealing.