Low-Temperature Surface Photochemistry of π-bonded Ethylene on Si(100)c(4x2)

We investigated the surface photochemistry of the pi-complex type weakly adsorbed ethylene on Si(100)c(4x2) at 50K, using high-resolution electron energy loss spectroscopy, quadrupole mass spectrometry, and photoelectron spectroscopy. At 50 K, both pi-complex precursor and di-sigma species coexist. We found that both the photoreaction from the pi-complex precursor to the di-sigma chemisorption and the photodesorption of ethylene occur upon photoirradiation. From the photodesorption signal of ethylene, we estimated the total cross section including these two photoinduced processes to be 1.1 X 10(-17)cm(2) at 365 nm. From the electronic structure of the adsorption system obtained in this study, we propose that a temporary negative ion of pi-bonded ethylene formed by a photogenerated hot-electron from the Si substrate is related to these processes. (C) 2009 The Japan Society of Applied Physics