TY - JOUR A1 - Lopez, A. A1 - Bitzer, Thomas A1 - Heller, Thomas A1 - Richardson, Neville V. T1 - Adsorption of water on alkoxy modified Si(1 0 0), Si(1 1 3) and Si(1 1 5) surfaces Y1 - 2001 ER - TY - JOUR A1 - Lopez, A. A1 - Heller, Thomas A1 - Bitzer, Thomas A1 - Chen, Q. A1 - Richardson, Neville V. T1 - The influence of sodium on the adsorption of water on SrTiO3(100)-1x1 surfaces Y1 - 2001 ER - TY - CHAP A1 - Heller, Thomas A1 - Lopez, Alberto A1 - Bitzer, Thomas A1 - Richardson, Neville V. A1 - Schmeißer, Dieter T1 - The Adsorption of Maleic Anhydride on Si(100)-2x1: A Combined HREELS and NEXAFS Study T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Due to the growing range of applications for organic materials considerable interest has been focused on the controlled growth of films on silicon substrates. Recently, it has been shown that ultra-thin oligimide films can be grown on Si(100)-2x1 with a direct Si-C linkage to the substrate. In this study, we have focused on the chemisorption of maleic anhydride (C4O3H2) on Si(100)-2x1. The combined HREELS data indicate that the adsorption of maleic anhydride on Si(100)-2x1 at low dosages occurs mainly through cycloaddition of the C=C bond to the dangling bonds of the Si-Si dimer analogous to the behaviour of ethene. The Si-Si dimer bonds are not involved in the chemisorption, as the continued observation of a 2x1 pattern in LEED shows. In the NEXAFS spectra, a π* resonance indicative of a C=C bond is absent upon exposure of the silicon substrate to maleic anhydride. At higher dosages, we observe chemisorbed maleic anhydride species, which are bonded to the Si surface atoms via a single Si-C linkage with preservation of the C=C double bond. In this case, the dissociated hydrogen bonds to one of the neighbouring Si atoms. Possible adsorption geometries will be discussed. KW - adsorption KW - maleic anhydride KW - High resolution electron energy loss spectroscopy (HREELS) KW - low-energy electron diffraction (LEED) KW - Near-edge X-Ray absorption spectroscopy (NEXAFS) Y1 - 2000 UR - http://www.dpg-verhandlungen.de/year/2000/conference/regensburg/part/o/session/11/contribution/56?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Heller, Thomas A1 - Lopez, Alberto A1 - Bitzer, Thomas A1 - Richardson, Neville V. A1 - Schmeißer, Dieter T1 - Isopropoxy induced stabilisation of the 2x1 reconstruction of Si(100) T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Alcohols are successfully employed as an additive in the anisotropic etching of silicon. In this HREELS study, we modelled the silicon/etching interface by the adsorption of alcohols (ethanol, isopropanol, n-propanol, tert-butyl alcohol) on Si(100)-2x1 and post-exposure to H2O under ultra high vacuum conditions. The vibrational data show that the adsorption of the alcohol molecules involves the cleavage of the O-H bond and the formation of a Si-O-C linkage to the alkoxy species. The dissociated hydrogen saturates one of the neighbouring dangling Si bonds. The Si-Si dimer bonds are not involved in the adsorption process. We observe a considerable chemisorption of water on the ethoxy and tert-butoxy passivated Si(100)-2x1 surface. From the disappearance of the 2x1 LEED pattern it can be concluded that the chemisorption of water occurs through a cleavage of the Si-Si dimer bond. In contrast, isopropoxy species on Si(100)-2x1 reduces dramatically the reactivity of Si(100)-2x1 towards water. Even following extreme exposures to water (1012 Torr s), a 2x1 LEED pattern was observed indicating the presence of intact Si-Si dimer bonds at the isopropoxy/Si(100)-2x1 surface. KW - alcohol adsorption KW - anisotropic etching KW - high resolution electron energy loss spectroscopy (HREELS) KW - low-energy electron diffraction (LEED) Y1 - 2000 UR - http://www.dpg-verhandlungen.de/year/2000/conference/regensburg/part/o/session/11/contribution/55?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - JOUR A1 - Lopez, A. A1 - Bitzer, Thomas A1 - Heller, Thomas A1 - Richardson, Neville V. T1 - Functional group selectivity in adsorption of 4-aminobenzoic acid on clean and Na modified Si(100)-2 x 1 surfaces Y1 - 2001 ER - TY - JOUR A1 - Bitzer, Thomas A1 - Lopez, A. A1 - Heller, Thomas A1 - Richardson, Neville V. T1 - The Adsorption of maleic anhydride on Si(100)-2x1: A combined HREELS and NEXAFS study Y1 - 2000 ER - TY - GEN A1 - Lopez, Alberto A1 - Heller, Thomas A1 - Bitzer, Thomas A1 - Richardson, Neville V. T1 - A vibrational study of the adsorption of glycine on clean and Na modified Si (100)-2x1 surfaces T2 - Chemical physics N2 - The chemisorption of glycine and its fully deuterated analogue, d(5)-glycine, deposited on the clean and Na modified Si(100)-2 x 1 surfaces, has been studied byhigh-resolution electron energy loss spectroscopy (HREELS) and ab initio methods. HREELS indicates that chemisorption of glycine and d(5)-glycine on Na/Si(100)-2 x1 occurs through cleavage of the OH and OD bonds in the carboxylic groups. The adsorbed species are bonded through the formation of an ionic bond between thedeprotonated carboxylate group and the adsorbed Na atom, leading to species in a bidentate coordination. In contrast, we observe monodentate glycinate andd(5)-glycinate species following the exposure of Si(100)-2 x 1 to glycine and deuterated glycine. The thermal stability of glycine on clean Si(100)-2 x 1 and on the Namodified surface has been studied by heating the substrate to various temperatures. KW - Silicon KW - Glycine KW - Sodium KW - Ab initio KW - HREELS Y1 - 2002 SN - 0301-0104 VL - 277 IS - 1 SP - 1 EP - 8 ER - TY - JOUR A1 - Lopez, A. A1 - Bitzer, Thomas A1 - Heller, Thomas A1 - Richardson, Neville V. T1 - Adsorption of maleic anhydride on Si(1 0 0)-2 x 1 JF - Surface Science Y1 - 2001 SN - 0039-6028 VL - 477 SP - 219 EP - 226 ER - TY - THES A1 - Heller, Thomas T1 - Molekulare Resonanzen im Wirkungsquerschnitt der Photoemission in den Valenzzuständen der stöchiometrischen und der mit Natrium belegten WO3 und TiO2 (110) 1x1 Oberfläche KW - WO3 KW - TiO2 KW - Photoelektronenspektroskopie KW - Natriumadsorption Y1 - 2002 SN - 3-8322-0742-2 PB - Shaker CY - Aachen ER - TY - CHAP A1 - Heller, Thomas A1 - Böhme, Oliver A1 - Schmeißer, Dieter T1 - Gap - Zustände in Wolframoxid WO3 - relaxierten Oberflächen T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Vorgestellt werden Arbeiten an dünnen WO3-Schichten, die durch Verdampfen aus einer Knudsenzelle im UHV präpariert wurden. Diese Filme sind im Rahmen der XPS-Analysen stöchiometrisch, ohne Gap-Zustände. Definierte Gap-Zustände bilden sich durch Relaxierung der Oberfläche: nach einigen Stunden im UHV, nach Heizen in Argon-Atmosphäre und nach Belegung mit Natrium. Die Charakterisierung dieser definierten Wolframoxid-Schichten erfolgt durch: 1.)XPS-Intensitäten 2.)detailierte Analyse der W4f-Rumpfniveaus durch Synchrotronstrahlung (Bessy, TGM 7) 3.)die Variation der Austrittsarbeit beim Heizen und bei Natrium-Belegung 4.)das Auftreten von Gap-Zuständen in der Bandlücke KW - WO3 KW - Röntgen-Photoelektronenspektroskopie (XPS) KW - Gapzustände Y1 - 1998 UR - http://www.dpg-verhandlungen.de/year/1998/conference/regensburg/part/o/session/11/contribution/102?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER -