Trapping-mediated chemisorption of ethylene on Si(001)-c(4 x 2).
Adsorption of ethylene molecules on Si(001)-c(4 x 2) was studied using scanning tunneling microscopy at low temperatures. Ethylene molecules trapped at the surface at 50 K were imaged only after decay to chemisorption, each bonding to a Si dimer. Atomic-scale observations of temperature-dependent kinetics show that the decay exhibited Arrhenius behavior with the reaction barrier of 128 meV in clear evidence of the trapping-mediated chemisorption, however, with an anomalously small preexponential factor of 300 Hz. Such a small prefactor is attributed to the entropic bottleneck at the transition state caused by the free-molecule-like trap state.
Chung
Chun-Hyung
CH
Department of Physics, Yonsei University, Seoul 120-749, Republic of Korea.
Jung
Woo-Jin
WJ
Lyo
In-Whan
IW