PHYSICS Colloquium
관련링크
본문
Adsorption of Simple Molecules on Si Surfaces: Long and Cold Look by Scanning
Tunneling Microscopy
연사: size=3>여인환[연세대]
size=3>일시: 2007 년 4 월 13 일 오후 3시
장소: 무은재 기념관 307호 (멀티미디어 강의실)
ABSTRACT:
interaction is crucial not only fundamentally, but also technologically to areas
as diverse as molecular electronics to catalysis. Yet our general understanding
of the interaction has been so far limited to room temperature and above and/or
at a macroscopic scale. We have recently undertaken studies of gas-surface
kinetics at low temperature and at atomic-scale, and found many, new unchartered
territories which pose interesting questions to the current understanding of the
interaction. In this talk, we will present our studies on adsorption of oxygen
and ethylene molecules on the technologically important Si(001)-c(4×2) surface
using low temperature scanning tunneling microscopy. At the early stage of
oxygen adsorption, reactions with Si atoms at S_B steps are dominant over those
at terraces by more than 2 orders of magnitude, and they proceed in two distinct
stages to high oxidation states, through the formation of -Si-O- chain
structures along the step edge. On the other hand, ethylene molecules dosed at
50 K decay thermally to "di-σ" chemisorption states, which exhibits Arrhenius
behavior with a small reaction barrier. Surprisingly the decay rate is found 10
orders of magnitude lower than a conventional estimate. Such a large suppression
of the reaction rate is interpreted by the entropic bottleneck at the transition
state induced by the free-molecule-like trap state. Our studies suggest that the
free-molecule-like trap state may be quite general, including the case of oxygen
molecules, and that the entropic bottleneck plays a crucial role at low
temperature reactions.
size=3>문의처: 강명호(054-279-2086, href=mailto:kang@postech.ac.kr>kang@postech.ac.kr)
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