Synchrotron radiation induced reactions on surfaces: mechanisms and applications

Abstract

In this paper we tabulate recent research that delves into the application of synchrotron radiation for inducing surface chemical reactions. We then present results from recent experiments designed to test whether surface photochemical reactions can be brought about by direct core-level excitation of the adsorbate, as opposed to an indirect mechanism where photoabsorption by bulk atoms produces secondary electrons that cause the reaction. Experiments were performed on SiF 4 adsorbed on Ge(100) at 30 K. It was found that direct excitation of Si2p core levels causes the reaction to occur. Finally we show the application of X-ray dependent surface photochemistry in two systems of technological relevance. The first is adamantane (C 10H 16) adsorbed on Si(111) at 85 K. X-rays with energies greater than the CK edge (284 eV) cause significant bond breaking and the formation of SiC. Lower energy X-rays appear to create adamantyl radicals which bond strongly with the substrate and are stable to 625 K. The second is Teflon where irradiation with photons with energies lower than 12 eV induces the desorption of relatively large fluorocarbon fragments, as compared to photolysis with photons of energies greater than 22 eV (C2s excitation).