Paper SS-ThP1
Adsorption, Photo-Fragmentation, and Ion-Desorption Pathways of Organic Molecules at Semiconductor Surfaces using Synchrotron Radiation Techniques

Thursday, October 23, 2008, 6:00 pm, Room Hall D

The chemistry of organic molecules on semiconductor surfaces has attracted much attention due to the perspective of the molecular wires, self-assembled monomolecular layer (SAM), and semiconductor-organic hybrid formation such as SiC. We have investigated the adsorption interaction, photo-dissociation, and ion-desorption of multifunctional organic molecules such as acetone [(CH3)2C=O] adsorbed on Si substrates. We used synchrotron radiation techniques including polarization-angular dependences of near-edge x-ray absorption fine structure (NEXAFS) and photon-stimulated ion-desorption (PSID). We measured photon-energy dependences of ion yields for a variety of fragments in the carbon 1s excitation region, along with the NEXAFS. We compare results for the following three systems: (1) dissociatively adsorbed monolayered molecules prepared at a room temperature (RT), (2) molecularly adsorbed monolayered molecules prepared by heating condensed molecules very slowly from liquid-N2 low temperatures (LT) to RT, and (3) multilayered molecules prepared at LT. The results showed that mass-patterns and excitation spectra of PSID depend dramatically on the chemical states of adsorbed systems. We conclude that PSID and NEXAFS techniques are useful tools to investigate chemical states such as configuration, orientation, and charge-transfer interaction of adsorbed molecules at surfaces.