1992 Fiscal Year Final Research Report Summary
STUDY ON SURFACE AND INTERFACE ELECTRONIC STRUCTURE DERIVED FROM THE DESIGNED TWO-DIMENSIONAL LATTICE.
| Project/Area Number |
03804027
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理化学一般
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| Research Institution | UTSUNOMIYA UNIVERSITY |
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Principal Investigator |
EGAWA Chikashi UTSUNOMIYA UNIVERSITY,DEPT. OF GENERAL EDUCATION, ASSOCIATIVE PROFESSOR, 教養部, 助教授 (30151963)
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| Project Period (FY) |
1991 – 1992
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| Keywords | DESIGNED TWO-DIMENSIONAL LATTICE / SURFACE ELECTRONIC STATE / SURFACE ACTIVATION / Rh(001) SURFACE / f.c.c. IRON THIN-FILM |
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| Research Abstract |
In order to measure the electronic states of f.c.c. iron thin-films epitaxially grown on a Rh(001) surface, we constructed an ultra-violet photon source consisted of an inlet system of purified helium and a compact and clean differential pumping unit aide by a turbo-molecular pump. The alignment of capillary tubes inserted in the discharge and differential parts enabled us to increase the intensity and stability of photon source and to measure the electronic states quickly.
We have investigated the reactivity of f.c.c. iron thin-films toward the adsorption of hydrogen and the surface reaction between adsorbed hydrogen and ethylene molecule. In contrast to the results reported on b.c.c. iron single crystal surfaces, the bonding energy of hydrogen to iron single layer on the Rh(001) surface is greatly reduced and the hydrogen desorbs from the surface at the temperature as low as 200 K. With the increase in the thickness of iron films above two-monolayer, the desorption temperature is grad
… More
ually shifted to 300 K and the sticking probability is reduced to one-tenth. The result corresponds to that observed on f.c.c. iron thin-films on Cu(001) surface. For the reaction of adsorbed hydrogen and ethylene, two desorption peaks are observed at 120 Kand above 200 K without the formation of ethane molecule. The latter is derived from the dehydrogenation of ethyl intermediate which is produced by adding of one hydrogen atom to ethylene molecule. The reactivity and stability of ethyl intermediate is also dependent on the thickness of iron overlayer.
We have studied the electronic states, particularly around Fermi level, by means of ultra-violet photoelectron spectroscopy. For the clean Rh(001) surface, the sharp photoemission due to d-band is observed at 0-3 eV below Fermi level. The electronic states of iron overlayers are obtained from the subtraction of the contribution of Rh substrate emission assuming the electron escape depth of 2.5 monolayer. The result shows the reduction of the Fermi level intensity in accordance with the shift toward to the lower binding energy for the first monolyer of iron thin-films. Further increase in the thickness of iron film induced the increase of the emission of Fermi level and the peaks at 1.5 and 3 eV. A new state close to the Fermi level appears at 8 ML. From these observations, it is turned out that the electronic structures of f.c.c. iron thin-films are closely related to their reactivity and surface structure. Less
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