• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.86-86
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• 2010

Water adsorption on Si(001)-c($4{\times}2$) surface is investigated at low temperature by using scanning tunneling microscope (STM) and ab initio pseudopotential calculations. $H_2O$ configurations of single and cluster of two molecules reveal "Y", "X" and "W" depressions as footprints on the surface. Atomic structures of $H_2O$ molecules, which are dissociatively adsorbed on the Si(001)-c($4{\times}2$) surface, are studied with simulated and STM images of the filled states. The generation processes of the growth configurations are systematically considered with elapsed time.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.268-268
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• 2013

Water molecules on a Ru(0001) surface are anomalously acidic compared to bulk water. The observation was made by conducting reactive ion scattering, reflection absorption infrared spectroscopy, and temperature-programmed desorption measurements for the adsorption of ammonia onto a water layer formed on Ru(0001). The study shows that the water molecules in the first intact $H_2O$ bilayer spontaneously release a proton to NH3 adsorbates to produce $NH_4{^+}$. However, such proton transfer does not occur for $H_2O$, OH, and H in a mixed adsorption layer or for $H_2O$ in a thick ice film surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.210.2-210.2
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• 2014

Recently, molybdenum disulfide (MoS2) nanostructures have been investigated for applications of lithium-ion batteries, solar cell, and gas sensors. In this regard, we have studied atomic and electronic properties of MoS2 nanostructures with adsorbed atoms and molecules using density functional theory calculations. Our calculations reveal that the several atoms such as H, C, N, and F are chemically bound to several sites on the two-dimensional (2D) MoS2 surface. On the other hand, various contamination molecules such as CO, CO2, NO, NO2, and NH3 do not bind to the surface. Next, adsorption of various molecules on the one-dimensional (1D) armchair MoS2 nanoribbon is investigated. Contrary to the case of 2D MoS2 monolayer surface, some molecules (CO and NO) are bound well to the edge of the MoS2 nanoribbon. We find that the molecular states due to adsorption are located near the Fermi level, which makes the band gap narrower. Therefore, we suggest that monolayer MoS2 nanoribbons be used as the gas sensors or detectors.

• Journal of The Korean Association For Science Education
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• v.26 no.7
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• pp.805-812
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• 2006

In this study the description patterns of chemistry textbooks on the boiling point elevation phenomenon and the understanding patterns of high school students, pre-service teachers and chemistry teachers were investigated. High school chemistry II textbooks developed in the 6th and 7th national curricula were analyzed and the conception patterns of subjects on this phenomenon were categorized using a questionnaire developed for this study. The description patterns of science textbooks were classified into three: 'decreasing of surface solvent molecules', 'attraction force between solvent and solute molecules' and 'decreasing of surface solvent molecules and attraction force between solvent and solute molecules'. In the result of the conception analysis, the ratio of 'attraction force between solvent and solute molecules' was high among students, pre-service teachers, and chemistry teachers. There was a propensity that they would like to explain the boiling point elevation in terms of enthalpy rather than entropy, and in order to analyze this propensity, follow-up interviews were carried out.

• Journal of Periodontal and Implant Science
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• v.41 no.6
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• pp.263-272
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• 2011

A number of surface modification techniques using immobilization of biofunctional molecules of Titanium (Ti) for dental implants as well as surface properties of Ti and Ti alloys have been developed. The method using passive surface oxide film on titanium takes advantage of the fact that the surface film on Ti consists mainly of amorphous or low-crystalline and nonstoichiometric $TiO_2$. In another method, the reconstruction of passive films, calcium phosphate naturally forms on Ti and its alloys, which is characteristic of Ti. A third method uses the surface active hydroxyl group. The oxide surface immediately reacts with water molecules and hydroxyl groups are formed. The hydroxyl groups dissociate in aqueous solutions and show acidic and basic properties. Several additional methods are also possible, including surface modification techniques, immobilization of poly(ethylene glycol), and immobilization of biomolecules such as bone morphogenetic protein, peptide, collagen, hydrogel, and gelatin.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.700-706
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• 1996

We present the results of molecular dynamics simulations of monolayers of long-chain alkyl thiol [S(CH2)15CH3] molecules on an air-solid interface using the extended collapsed atom model for the chain-molecule and a gold surface for the solid surface. Several molecular dynamics simulations have been performed on monolayers with areas per molecule ranging from 18.30 to 32.10 Å2/molecule. It is found that there exist three possible transitions: a continuous transition characterized by a change in molecular configuration without change in lattice structure, a sudden transition characterized by the distinct lattice defects and perfect islands, and a third transition characterized by the appearance of a random, liquid-like state. The analysis of probability distributions of the segments shows that the structure of the chain-molecules at the air-solid interface is completely different from that at the air-water interface in the view of the degree of overlap of the probability distributions of the neighbor segments. The calculated diffusion coefficients of the chain-molecules on the monolayers seem to be not directly related to any one of the three transitions. However, the large diffusion of the molecules enhanced by the increment of the area per molecule may induce the second transition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1014-1018
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• 2005

The purpose of this study is to obtain strong bond strength at the interface between piezoelectric substrates and semiconductor thin films to be applied for the manufacture of high-performance acoustic wave semiconductor coupled device. For this purpose, we have compared and examined the effects of different surface treatment methods on hydrophile properties at the surface of the piezoelectric substrates. Moreover, we have observed the effect of microwave and laser on the elimination of water molecules at the interface. As for the piezoelectric substrates, dry method for surface treatment was found to be superior in the control of hydrophilicity of the surface compared to wet method. On the other hand, both microwave and laser were found to be effective in the elimination of water molecules in the interface.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2930-2934
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• 2009

Surface-enhanced Raman Scattering (SERS) spectroscopy is applied to the study of the adsorption of benzoimidazolic fungicides benzimidazole (BIZ) and thiabendazole (TBZ) on silver mirrors. The influence of pH on the adsorption mechanism was investigated. In case of BIZ, two different adsorption mechanisms are deduced depending on the experimental conditions: via the $\pi$ electrons of the ring in neutral conditions and through an ionic pairing of protonated nitrogen atom with the chloride adsorbed on the metal surface. The SERS spectra of TBZ revealed that most molecules were adsorbed on silver surface by the ${\pi}$ electrons in neutral and acidic conditions but in acid conditions, some molecules were adsorbed via the sulfur and nitrogen atoms tilted slightly to the surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.135-135
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• 2013

The electronic and adsorption structures of Mg and p-tert-butylcalix[4]arene (p-TBCA) adsorbed onto a Ge(100) surface under a variety of sample conditions were characterized using high-resolution photoemission spectroscopy (HRPES) and their corresponding DFT calculation results. Interestingly, after 0.10 ML p-TBCA molecules had been adsorbed onto a Ge(100) surface, subsequent adsorption of a small amount of metallic Mg (~0.10 ML) resulted in the formation of a capped structure inside the pre-adsorbed p-TBCA molecules. The adsorption structures resulting from further deposition of Mg (~0.50 ML) onto the Ge(100) surface were monitored based on the surface charge state and Mg 2s core level spectrum. Work function measurements clearly indicated the electronic structures of the Mg and p-TBCA adsorbed onto the Ge(100) surface. Moreover, we confirmed that three different adsorption structures are experimentally favorable at room temperature through DFT calculation results.

• Bulletin of the Korean Chemical Society
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• v.22 no.5
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• pp.455-462
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• 2001

The time-dependent tracking inversion method is studied to extract the potential energy surface of the electronic excited state in the photodissociation of triatomic molecules. Based on the relay of the regularized inversion procedure and time-dependent wave packet propagation, the algorithm extracts the underlying potential energy surface piece by piece by tracking the time-dependent data, which can be synthesized from Raman excitation profiles. We have demonstrated the algorithm to extract the potential energy surface of electronic excited state for NO2 molecule where the wave packet split on a saddle-shaped surface. Finally, we describe the merits of the time-dependent tracking inversion method compared with the time-independent inversion method and discussed several extensions of the algorithm.