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The reaction of copper and calcium dipivaloymethanates (Cu(DPM)2 and Ca(DPM)2) with hydroxyls on oxide surface
A59 498
Surface Science 242 (1991) 498-502 North-Holland
Chemical reactivity of the Si(100)(2 x 1)-K surface: electron energy loss spectroscopy and thermal desorption studies M. Nishijima, S. Tanaka 1, N. Takagi and M. Onchi * Department of Chemistry, Faculty of Science, Kyoto University, Kyoto 606, Japan Received 11 May 1990; accepted for publication 7 June 1990 The adsorbed states of K atoms on the Si(100X2 × 1) surface and the interactions of the K-covered surface with several gases, i.e., H, 02, CO and HCOOH, have been studied mainly by the use of high-resolution electron energy loss spectroscopy (EELS) and thermal desorption spectroscopy (TDS). Experimental evidence is given for the existence of two chemisorbed states of K atoms on the Si(100X2 × 1) surface. Two adsorbed states of O atoms were found on the Si(100X2 × 1)-K surface. HCOO adspecies of an ionic character exist on the Si(100X2 × 1)-K surface.
Surface Science 242 (1991) 503-507 North-Holland
503
Synthesis of metastable surface complexes by chemical reactions N and N H x complexes on Pd(100), Rh(100) and Pt-Rh(100) Ken-ichi Tanaka *, Taro Yamada and B.E. Nieuwenhuys 1 The Institute for Solid State Physics, The University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106, Japan Received 15 May 1990; accepted for publication 18 June 1990 Pd(100), Rh(100), Pt(100) and Pt-Rh(100) are inert for the dissociative adsorption of N 2. We succeeded to prepare a surface nitride with a c(2 × 2) structure on Pd(100), Rh(100) and Pt-Rh(100) surfaces by performing the catalytic reaction of NO + H2 N(a) + H20. On Pt(100), however, the accumulation of N atoms was difficult. Formation of c(2 × 2)-N on a Pt-Rh(100) surface indicates equal affinity of N atoms to the Pt and Rh atoms on the alloy surface. When the c(2 × 2)-N surface is exposed to H 2, a prominent loss-peak appears at 3200-3240 cm -1. In situ EELS experiments of the c(2 × 2) surfaces in 10-7-10 - s Tort of H2 showed that the loss peak intensity for the N - H vibration obeys to a half order dependence in hydrogen pressure, which su~ests that the predominant N-hydrogen adsorption complex is NH and not NH 2. The isotope effect for equilibrium of NH and ND is very small on Pd(100), Rh(100) and Pt-Rh(100) surfaces.
508
Surface Science 242 (1991) 508-512 North-Holland
The reaction of copper and calcium dipivaloylmethanates (Cu(DPM) 2 and Ca(DPM) 2) with hydroxyls on oxide surface Rika Sekine, Maki Kawai, Tokihisa Hikita and Takashi Hanada Research Laboratory of Engineering Materials, Tokyo Institute'of TechnoloD,, 4259 Nagatsuta, Midori-ku, Yokohama, 227, Japan and Institute of Physical and Chemical Research, Wako-shi, Saitama 351-01, Japan Received 16 May 1990; accepted for publication 29 June 1990 Selective and stoichiometric reactions between surface hydroxyl groups (OH) on SiO 2 and calcium dipivaloylmethanate (Ca(DPM)2) were investigated by infrared (IR) and photoelectron (XPS) spectroscopies. The stoichiometric ratio of initial surface OH and adsorbed Ca(DPM)2 is estimated from IR absorbance to be ca. (2-3): 1. Introduction of water vapor at 673 K to this surface results in the removal of ligand DPM from the adsorbed Ca(DPM)2 , leaving the Ca on the surface. The reactive property of Ca(DPM) 2 is identical to that of Cu(DPM)2, previously l~-ported by us. A similar reaction on the surface of single crystal SrTiO3(100 ) with the Cu(DPM)2 is also carried out.
Surface Science 242 (1991) 498-502 North-Holland
Chemical reactivity of the Si(100)(2 x 1)-K surface: electron energy loss spectroscopy and thermal desorption studies M. Nishijima, S. Tanaka 1, N. Takagi and M. Onchi * Department of Chemistry, Faculty of Science, Kyoto University, Kyoto 606, Japan Received 11 May 1990; accepted for publication 7 June 1990 The adsorbed states of K atoms on the Si(100X2 × 1) surface and the interactions of the K-covered surface with several gases, i.e., H, 02, CO and HCOOH, have been studied mainly by the use of high-resolution electron energy loss spectroscopy (EELS) and thermal desorption spectroscopy (TDS). Experimental evidence is given for the existence of two chemisorbed states of K atoms on the Si(100X2 × 1) surface. Two adsorbed states of O atoms were found on the Si(100X2 × 1)-K surface. HCOO adspecies of an ionic character exist on the Si(100X2 × 1)-K surface.
Surface Science 242 (1991) 503-507 North-Holland
503
Synthesis of metastable surface complexes by chemical reactions N and N H x complexes on Pd(100), Rh(100) and Pt-Rh(100) Ken-ichi Tanaka *, Taro Yamada and B.E. Nieuwenhuys 1 The Institute for Solid State Physics, The University of Tokyo, 7-22-1 Roppongi, Minato-ku, Tokyo 106, Japan Received 15 May 1990; accepted for publication 18 June 1990 Pd(100), Rh(100), Pt(100) and Pt-Rh(100) are inert for the dissociative adsorption of N 2. We succeeded to prepare a surface nitride with a c(2 × 2) structure on Pd(100), Rh(100) and Pt-Rh(100) surfaces by performing the catalytic reaction of NO + H2 N(a) + H20. On Pt(100), however, the accumulation of N atoms was difficult. Formation of c(2 × 2)-N on a Pt-Rh(100) surface indicates equal affinity of N atoms to the Pt and Rh atoms on the alloy surface. When the c(2 × 2)-N surface is exposed to H 2, a prominent loss-peak appears at 3200-3240 cm -1. In situ EELS experiments of the c(2 × 2) surfaces in 10-7-10 - s Tort of H2 showed that the loss peak intensity for the N - H vibration obeys to a half order dependence in hydrogen pressure, which su~ests that the predominant N-hydrogen adsorption complex is NH and not NH 2. The isotope effect for equilibrium of NH and ND is very small on Pd(100), Rh(100) and Pt-Rh(100) surfaces.
508
Surface Science 242 (1991) 508-512 North-Holland
The reaction of copper and calcium dipivaloylmethanates (Cu(DPM) 2 and Ca(DPM) 2) with hydroxyls on oxide surface Rika Sekine, Maki Kawai, Tokihisa Hikita and Takashi Hanada Research Laboratory of Engineering Materials, Tokyo Institute'of TechnoloD,, 4259 Nagatsuta, Midori-ku, Yokohama, 227, Japan and Institute of Physical and Chemical Research, Wako-shi, Saitama 351-01, Japan Received 16 May 1990; accepted for publication 29 June 1990 Selective and stoichiometric reactions between surface hydroxyl groups (OH) on SiO 2 and calcium dipivaloylmethanate (Ca(DPM)2) were investigated by infrared (IR) and photoelectron (XPS) spectroscopies. The stoichiometric ratio of initial surface OH and adsorbed Ca(DPM)2 is estimated from IR absorbance to be ca. (2-3): 1. Introduction of water vapor at 673 K to this surface results in the removal of ligand DPM from the adsorbed Ca(DPM)2 , leaving the Ca on the surface. The reactive property of Ca(DPM) 2 is identical to that of Cu(DPM)2, previously l~-ported by us. A similar reaction on the surface of single crystal SrTiO3(100 ) with the Cu(DPM)2 is also carried out.