• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.157-157
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• 2000

The adsorption processes of methyl chloride on Si(100)-2$\times$1 have been studied by low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and semiempirical PM3 calculations. The dissociative adsorption of the methyl chloride on Si(100) takes place without breaking of the silicon dimer with high efficiency. For adsorption at the room temperature, the existence of a precursor state is confirmed by the behavior of the sticking probability depending on the coverage and temperature. From AES measurements, the determined activation barrier of adsorption ($\Delta$ Hads) is -28.4 kj/mol. This results indicate that the dissociative process is nonactivated. The optimized precursor state of CH3Cl on the Si(100)-2$\times$1 surface was determined by PM3 calculations based on a cluster model.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.203-203
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• 2011

The importance of stepped single-crystal surfaces as model catalysts has been well recognized [1]. We re-investigated the adsorption properties of $H_2$ and CO, most important species in platinum-based catalysts, on nearly defect-free and highly stepped surfaces of one and the same Pt(111) crystal. While both being symmetric and single-peaked from the nearly defect-free surface, temperature-programmed desorption (TPD) spectra from the highly stepped surface saturated at 90 K with H and CO were triply- and doubly-peaked, respectively. Once pre-adsorbed, CO preempted step and then terrace sites, inhibiting the dissociative $H_2$ adsorption completely. Pre-adsorbed H inhibited the CO adsorption on terrace sites only, leaving defect sites intact for CO adsorption even at the saturation H precoverage. On defect-free Pt(111), while pre-adsorbed CO inhibited the dissociative $H_2$ adsorption completely, pre-adsorbed H could not inhibit the CO adsorption completely. These intriguing, but interesting results are discussed in terms of energetics/kinetics and the role of surface step sites in the dissociative adsorption of $H_2$ on Pt(111) [2].

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.332-332
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• 2011

The adsorption and desoprtion properties on Pt(111) of chiral molecules, propylene oxide (PO) and 1,3-dimethyl butylamine (DMBA), have be characterized in utrahigh vacuum. Precision-doses of PO and DMBA onto a Pt(111) surface at 90 K have been achieved with a directed tubular molecular doser controlled by a micron-sized orifice and the reservoir gas pressure. Temperature-programmed desorption (TPD) mass spectra have been employed together with low-energy electron diffraction (LEED) analyses. In addition to the separate adsorption behaviors of PO and DMBA, the enantioselective adsorption of R- and S-PO on Pt(111) precovered with R- or S-DMBA have been investigated thoroughly, and the results will be presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.212-212
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• 2012

The Coverage dependent attachment of multifunctional groups included in threonine molecules adsorbed to Ge (100)$-2{\times}1$ surface was investigated using core-level photoemission spectroscopy (CLPES) and density functional theory (DFT) calculations. The core-level spectra at a low coverage indicated that the both carboxyl and amine groups participated in the bonding with the Ge (100) surface by "O-H dissociated and N-dative bonded structure". However, at high coverage level, additional adsorption geometry of "O-H dissociation bonded structure" appeared possibly to minimize the steric hindrance between adsorbed molecules. Moreover, the C 1s, N 1s, and O 1s core level spectra confirmed that the carboxyl oxygen is more competitive against the hydroxymethyl oxygen in the adsorption reaction. The adsorption energies calculated using DFT methods suggested that four of six adsorption structures were plausible. These structures were the "O-H dissociated-N dative bonded structure", the "O-H dissociation bonded structure", the "Om-H dissociated-N dative bonded structure", and the "Om-H dissociation bonded structure" (where Om indicates the hydroxymethyl oxygen). These structures are equally likely, according to the adsorption energies alone. Conclusively, we investigate in threonine on Ge (100) surface system that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at low coverage and high coverage.

• Proceedings of the Korean Vacuum Society Conference
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• 2007.02a
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• pp.76-76
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• 2007

• Proceedings of the Korean Vacuum Society Conference
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• 2005.02a
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• pp.62-62
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2009.08a
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• pp.325-325
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.151-151
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• 2008

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.227-227
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• 2008