Ar 이온에 의해 Sputtering된 Pt(111) 표면의 NO 흡착

이순보,부진효,이성용,박종윤,곽현태 성균관대학교 기초과학연구소 1992 論文集 Vol.43 No.1

Adsorption of nitric oxide on the Pt(111) surface sputtered by Ar-ion has been studied using thermal desorption spectroscopy, Auger electron spectroscopy, and low energy electron diffraction. A thermal desorption spectrum obtained from the perfect Pt(111) saturated with NO at 300K is quite simillar to those reported previously. The main portion desorbs at about 370K(α-state) with a shoulder at about 470K(β-state). The chemisorption of nitric oxide is predominantly molecular on the Pt(111) surface, accompanied by a small amount of dissociation which becomes negligible when the Pt(111) surface is perfect. When the Pt(111) surface is sputtered by Ar-ion with 2KeV, the thermal desorption spectrum becomes quite complex. The shoulder peak, which appears on the perfect surface spectrum, increases with Ar-ion sputtering time. The maximum desorption spectra of N₂ and N₂O are observed simultaneously between 470 and 600K. The desorption mechanisms for N₂O are proposed. The increasing N₂ with the β-state of NO indicates that the β-state is a precursor to the NO dissociation.

다결정 Ni 표면과 CO의 상호작용

李淳甫,이순영,부진효 성균관대학교 기초과학연구소 1985 論文集 Vol.36 No.2

The chemisorption properties of CO on polycrystalline Ni surface are studied by XPS at 150K, 300K and 400K. The CO are adsorbed only molecularly at lower temperature than room-temperature having a adsorption energy of about 87KJ/mol. At 400K, the CO are dissociated, so that the carbon remains as 'carbidic' carbon on the surface, which is stable at lower temperature about 620K, and above this temperature it is transformed to graphite. On the other hand, atomic oxygen species on the surface may be reduced by CO in gas phase. A possible mechanism for the formation of 'carbidic' carbon is proporsed.

다결정니켈 표면에서의 산소와 일산화탄소간의 상호작용

이순보,부진효,김우섭 성균관대학교 기초과학연구소 1989 論文集 Vol.40 No.2

Interactions between oxygen and carbon monoxide on Ni surface were studied by means of XPS at room temperature in UHV system attached with a. quadrupole mass spectrometer. Adsorption of CO on Ni surface precovered with oxygen are followed by three step. It was noted that CO₂ gas are formed by reaction of preadsorbed oxygen and CO molecules at initial step, and the second step is followed that precovered oxygen and CO molecules are coadsorbed, and during the high CO exposure the less pread-sorbed oxygen is, the more adsorbed CO. It could be attributed to the fact that the existence of oxygen on the Ni surface reduced the sticking coefficient of CO. Dissociative adsorption of O₂ on Ni surface were inhibited by the preadsorbed CO molecule at initial oxygen exposure. The dissociative adsorption of the preadsorbed CO increased with increasing exposures of O₂ and Ar. This was very well explained by the model of a collision-energy transfer, that a collision between the preadsorbed CO and O₂ or Ar gas cause to increase an amplitude of vibration mode contributed to dissociative adsorption so that the preadsorbed CO molecule is dissociated by the interaction of oxygen atom of adsorbed CO and Ni atoms.

XPS Studies of Oxygen Adsorption on Polycrystalline Nickel Surface (II)

이순보,부진효,함경희,안운선,이광순,Lee Soon-Bo,Boo Jin-Hyo,Ham Kyoung-Hee,Ahn Woon-Sun,Lee Kwang-Soon Korean Chemical Society 1988 Bulletin of the Korean Chemical Society Vol.9 No.1

The isotherms of oxygen chemisorption on polycrystaline nickel surface are obtained at various temperatures between 298K and 523K from intensity measurernent of O 1s xps peaks, and the activation energy of the chemisorption is estimated as a function of the coverage. The activation energy extrapolated to zero coverage is found to be -5.9 kJ/mol. The negative activation energy can be taken as a strong implication of the propriety of a currently accepted chemisorption model, in which molecularly adsorbed precursor state is assumed to exist. The residence time of this precursor state is estimated by assuming a molecularly physisorbed state for the precursor state and assuming a pairwise interaction energy of Lennard-Jones 12-6 potential between an admolecule and each substrate nickel atom. The sticking coefficients are also calculated from the isotherms. The calculated results agree well with those obtained by others with different methods.

열탈착 분석법에 의한 Pt(111) 표면위의 NO와 CO의 흡착

이순보,박종윤,곽현태,부진효,강용철 성균관대학교 1992 論文集 Vol.42 No.2

The adsorptions of nitric oxide and carbon monoxide on Pt(111) surfaces have been studied by using LEED, AES, and TDS(Thermal Desorption spectroscopy). The adsorbed species of NO is predominantly molecular on the Pt(111) surface at room temperature. A main desorption peak of TDS is attributed to the molecular adsorption at 360K. With increasing No exposures, a shoulder peak at 480K which may be attributed to the defect site adsorption is appeared. The desorption rate order for No desorption is 1st order and the desorption energy for NO calculated by Redhead equation assuming pre-exponential factor v_1=10^13 sec^-1 is 21.7Kcal/mol. The adsorption of carbon monoxide is also molecular on Pt(111) surface at room temperature. The TDS results showed only a single broad peak at 460K, which is attributed to molecular adsorption. The desorption order for CO desorption is 1st order as well as NO and the desorption energy for CO is 28Kcal/mol.

다결정 니켈 표면에서의 CO 와 $O_2$의 공동흡착

이순보,부진효,김우섭,안운선,Soon Bo Lee,Jin Hyo Boo,Woo Sub Kim,Woon Sun Ahn 대한화학회 1993 대한화학회지 Vol.37 No.12

상온에서 다결정 니켈 표면에서의 CO와 산소의 공동흡착을 XPS를 이용하여 연구하였다. 산소가 미리 흡착된 다결정 니켈 표면에서의 CO 흡착은 다음의 세 단계로 일어나고 있음을 발견하였다. 즉 초기의 낮은 CO 노출량에서는 니켈 표면에 미리 흡착된 산소와 CO가 일부 반응하여 $CO_2$가 형성되어 $CO_2$로 탈착하며, CO 노출량이 점차적으로 증가함에 따라 CO가 산소와 공동흡착을 일으키며, CO 노출량이 높아지면 미리 흡착된 산소의 양이 적을수록 더 많은 CO가 흡착됨을 관측하였다. 이것은 니켈 표면에 미리 존재하는 산소의 덮임율이 증가함에 따라 CO의 점차율이 감소하고 동시에 CO의 상대적인 흡착자리가 감소하기 때문으로 해석하였다. 한편 CO가 미리 흡착된 다결정 니켈 표면에 산소를 흡착시키면 산소 노출량이 낮을 때는 미리 흡착된 CO가 산소의 흡착을 저해하며, 산소 노출량이 증가하면 CO가 해리흡착되고, 이와 동시에 산소가 니켈 표면에서 해리흡착되어 NiO층을 빠른 속도로 형성함을 관측하였다. CO의 해리흡착은 흡착된 CO와 기체상의 $O_2$의 충돌에 의한 에너지 전이 때문인 것으로 해석된다. The coadsorption of carbon monoxide and oxygen on polycrystalline nickel surface has been studied using XPS at the room temperaure. The adsorption of CO on the nickel surface precovered partially with oxygen is found to take place by the following steps: The CO molecules react with the preadsorbed oxygen atoms to liberate $CO_2$ gas at the initial stage of low CO exposures, and they are coadsorbed gradually with the increasing CO exposures. The extent of coadsorption at the higher CO exposures is found to decrease with the increasing degree of oxygen preadsorption. This finding is explained in terms of the reduced adsorption site for CO as a consequence of oxygen preadsorption. The CO molecules preadsorbed on the nickel surface inhibited the adsorption of $O_2$ molecules. The increase of oxygen exposure led to the dissociation of preadsorbed CO, and the NiO layers were formed concurrently. The dissociation was rendered to arise from an oxygen-to-CO energy transfer.

초고진공 장치의 설계 및 제작과 LEED Optics에 의한 Auger Electron Spectrometer의 분해능 측정

이순보,박종윤,곽현태,부진효,이성용 성균관대학교 1992 論文集 Vol.42 No.2

A multipurpose Ultra High Vacuum chamber was designed and constructed in this laboratory. This enables us to be equipped with various analytical instruments such as Ar-ion gun LEED optics, Electron analyzer, and Quadrupole mass spectrometer etc. The 4-Grid LEED optics, a product of Omicron company in West Germany, was equipped with the UHV chamber and the LEED power supply was designed by this group. Turbo-C language figured out Auger spectra of the ad-species by means of the computer interface. The resolution of Auger electron spectrometer was measured with a constant primary electron beam energy. The results showed that the resolution was independent of the primary electron beam energy, but depends on the modulation voltage. Also, it was revealed that the resolution of 4-Grid optics was more improved than that of 3-Grid optics.

X-ray 광전자 분광법의 원리와 응용

이순보(Soon-Bo Lee),부진효(Jin-Hyo Boo) 한국표면공학회 1990 한국표면공학회지 Vol.23 No.3

AES-LEED 장치의 설계 및 제작과 Ni / Pt(111)계에 관한 연구

이순보(S. B. Lee),부진효(J. H. Boo),이성용(S. Y. Lee),박종윤(C. Y. Park),곽현태(H. T. Kwak) 한국진공학회(ASCT) 1993 Applied Science and Convergence Technology Vol.2 No.2

본 연구에서는 표면 분석 장비에 필요한 초고진공 용기를 설계 제작하였으며, LEED optics를 이용한 AES와 LEED 제어 장비를 설계하여 제작하였다. 제작된 일련의 장비들을 이용하여 LEED optics의 전자에너지 분해능을 측정하고, Pt(111) 표면에 증착된 Ni의 성장양식을 단분자층과 단분자층의 형성모델을 가정하여 증착된 Ni의 두께를 Auger signal의 비로부터 구하였다. Ultra High Vacuum chamber for surface analysis and a series of AES-LEED controllers for LEED optics was designed and constructed. Electron energy resolution of LEED optics was tested. On the basis of the layer by layer mode, thickness of evaporated Ni on Pt(111) was calculated from the Auger signal ratio.

Methanol Decomposition on Ni(100) Preadsorbed with Sulfur

Lee, Soon-Bo,Madix, R.J. 成均館大學校 科學技術硏究所 1983 論文集 Vol.34 No.2

니켈표면에 흡착된 황의 덮힘율이 θ_s = 0와 θ_s = 0.5(8.0 x 10 exp(-14) atomas/㎠) 사이에서 Ni(100) 표면에 CH_3OH 분해에 대한 황의 효과를 프로그램된 반응 분광법으로 정량적인 연구를 하였다. 덮힘율이 θ_s = 0.20에서는 메특시 (CH_3O)의 중간체가 실온이상에서 안정했으며 CH_3OH의 탈수소화 선택성은 H_2CO가 생성되는 쪽으로 이동되었다. θ_s = 0.38에서는 순수한 Ni(100)의 CO 탈착스펙트럼의 최고점은 보다 낮은 온도에서 2개의 스펙트럼(β_1, β_2)으로 뚜렷하게 나타났다. 또한 CH_3OH가 H_2CO와 H_2로 분해되는 부분 탈수소화가 일어났으며 형성된 H_2CO의 양은 최대가 되었다. 4중대칭을 이루고 있는 오목한 곳에 미리 흡착된 CO는 흡착된 메특시(CH_3O)의 형성을 1대1로 방해아여 부분 탈수소화가 일어나지 못하게 한다는 것을 알았다. The surface coverage of sulfur on Ni(100) was varied between zero and 8.0 x 10 exp(14) atoms/㎠ in order to quantify its effect on CH_3OH decomposition by temperature programmed reaction spectroscopy. At a sulfur coverage of θ_s = 0.20 the methoxy intermediate became stable above room temperature, and the dehydrogenation selectivity shifted toward H_2CO. At θ_s = 0.38 the CO desorption peak characteristic of clean Ni(100) was extinguished and was replaced by two distinct peaks at lower temperature (β_1 and β_2). Also at this coverage only partial dehydrogenation of CH_3OH to H_2CO and H_2 occured, and the amount of H_2CO formed was maximized. It was found that CO preadsorbed into four-fold hollow sites poisoned the patial dehydrogenation in a one-to-one fashion by blocking formation of adsorbed methoxy intermediates.