Münster 1997 – scientific programme

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O: Oberflächenphysik

O 16: Dynamik der Adsorption/Desorption

O 16.7: Talk

Tuesday, March 18, 1997, 11:00–11:15, PC 4

The photochemical routes to desorption and fragmentation of disilane adsorbed on Si(100) — •Steven Wright, Olaf Dippel, and Eckart Hasselbrink — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin

The photochemical mechanisms leading to the formation of silicon-containing radical species and the photodesorption of intact disilane molecules have been explored. Time-of-flight (ToF) mass spectroscopy was used to identify and characterise the products ejected into the gas phase whereas electron energy loss spectroscopy (EELS) was used to investigate reactions of the radical species with the surface itself. Illumination of thick films of disilane condensed on a hydrogen passivated Si(100) surface yielded radicals containing one silicon atom in addition to a smaller amount of photodesorbed disilane. Some of these radicals react with other disilane molecules in the film to give eventually silane and molecular hydrogen but EELS shows that there is also reaction with the surface. At submonolayer coverages, the desorbing flux is predominantly photodesorbed disilane but we can, nevertheless, identify some fragmentation products and reaction with the surface. Substrate mediated and direct excitation mechanisms leading to fragmentation or desorption will be proposed and possible epitaxial growth processes will be described.