ABSTRACTArF (193 nm) and KrF (248 nm) laser-induced dissociation of Al2(CH3)6 (TMA) adsorbed on Si(100) surfaces have been investigated using x-ray photo-electron, ultraviolet photoelectron, and high-resolution electron energy loss spectroscopies (XPS, UPS, and HREELS). UPS and XPS valence spectra from the adlayer contained three broad peaks near 4.5, 7.5, and 14.5 eV below the Fermi level whose positions were in agreement, based upon molecular orbital calculations, with those expected for TMA dimers. Angle-resolved XPS measurements indicated a splitting in both the Al 2p and Si 2p levels which was interpreted as evidence for TMA dimer molecules being adsorbed with the long (i.e. Al-Al) axis perpendicular to the surface. The HREELS adlayer spectrum consisted of three clusters of peaks located near 86 meV (methyl rocking and Al-C stretch), 170 meV (methyl deformation), and 362 meV (C-H stretch). Changes in the XPS, UPS, and HREELS spectra were monitored as a function of ArF and KrF laser irradiation. No-changes were observed for KrF irradiation with intensities up to 200 mJ-cm . However, ArF laser irradiation resulted in changes in both the XPS and HREELS spectra which indicated TMA dissociation and the desorption of methyl groups. Nevertheless, even after 104 20 mJ-cm-2 ArF pulses most of the carbon-containing species remained. Higher intensities, up to 200 mJ-cm-2, resulted in the formation of compounds which were stable on the surface.
Detailed Structural Characterization of Sphingolipids via 193 nm Ultraviolet Photodissociation and Ultra High Resolution Tandem Mass Spectrometry