LEED and AES studies of chemisorption resulting from low exposures of C₂H₄, CO, and PH₃ to the (0001) surface of zirconium

Abstract

. Can. J. Chem. 66, 3157 (1988). Low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) have been used to study for the first time the chemisorption systems formed on the (000 1 ) surface of zirconium by exposing to C2H4, CO, and pH3 in the one to ten Langmuir regime. The adsorptions are done at room temperature, but there is subsequent heating to optimize the surface ordering. The main observations are as follows: ( i ) after heating C2H4-covered surfaces to effect hydrogen desorption, the remaining carbon can form two different ordered (1 X I)-C structures; (ii) CO forms both (2x2)-and (I X 1)-type structures; (iii) the temperature at which the bulk diffusion of oxygen becomes significant, as determined by AES, is about 40°C greater on a CO-treated surface than for an 02-treated Zr(000 1) surface; and (iv) heating a pH3-covered surface can yield a weakly-ordered (3 X3)-P structure. The observation (iv) contrasts with that for the analogous surface prepared previously with H2S; the poorly developed (3 X 3)-P surface structure results from the fact that the temperatures required for surface ordering overlap with those which yield a loss of phosphorus from the surface region.J. R. Lou, P. C. WONG et K. A. R. MITCHELL. Can. J. Chem. 66, 3157 (1988). Faisant appel 2 la diffraction Clectronique de faible Cnergie (LEED) et i la spectroscopie Clectronique de Auger (AES), on a CtudiC pour la premitre fois les systkmes de chemisorption formCs a la surface (000 1 ) du zirconium expose au C2H4, au CO et au pH3 dans l'un des dix rCgimes de Langmuir. On a realist les adsorptions a la temptrature ambiante avec un chauffage subsCquent pour optimiser l'ordonnance la surface. Les principales observations sont les suivantes : ( i ) apr2s le chauffage des surfaces couvertes de C2H4, pour affecter la dCsorption de l'hydrogtne, les atomes de carbone restants peuvent former deux diffkrentes structures ordonnCes de type (I x 1)-C; (ii) le CO forme deux structures de type (2 X2) et (1 X 1); (iii) la temperature i laquelle le gros de la diffusion de l'oxygkne devient significative, telle que determinee par AES, est plus Clevte d'environ 40°C pour une surface traitCe au CO que pour une surface de Zr(000 1 ) traitte a I'oxygkne et (iv) une surface couverte de pH2 peut donner une structure P de type (3x3) faiblement ordonnCe. L'observation (iv) contraste avec celle relative i la surface analogue prCparCe antkrieurement avec du H2S. La structure P de type (3 X 3) faiblement dCveloppCe rCsulte du fait que la temperature requise pour l'agencement de la surface rejoint celles qui conduisent 1 une perte de phosphore i partir de la surface.[Traduit par la revue]

Temperature programmed desorption study of C6H12∕Zr(0001)

“…3. LEED intensity analysis has confirmed an ordered ͑1 ϫ 1͒-C structure in a study of C 2 H 4 on Zr͑0001͒, 15 and it is likely that similar structures are present in our work. The electron fluence was 9 ϫ 10 16 electrons/ cm 2 for the latter data set.…”

Potential Energy Surfaces for Tc + CO, Re + CO, and Ta + CO and Periodic Trends of the Second- and Third-Row Transition Metals Interaction with CO

“…The gross Mulliken population of the a 6 S ground state of the Tc atom is computed as 4d 5.015 5s 1.847 , which is in excellent agreement with the anticipated configuration of 4d 5 5s 2 . We have obtained an averaged dissociation limit for the 4 Π, 4 ∆, and 4 Φ states of TcCO since the 4 P, 4 F, and 4 G atomic spectral terms of the technetium atom are quite close to each other, 61 and it is thus difficult to make a definitive determination of the atomic states from the molecular computations.…”

“…These studies have dealt with a variety of species of transition metals such as clusters, alloys, and inorganic salts, and especially those pertinent to the second- and third-row transition metals. A primary motivation for such studies is that these species play an important role in the catalytic and chemisorption processes. − With these efforts, not only is the determination of the activity for certain chemical reactions available, but also the mechanism of heterogeneous catalysis concerning active sites of transition metals can be investigated. In recent years, synthesis and characterization of organic metal complexes containing carbonyl ligands have received considerable attention. − It has been shown that these catalysts exhibit enhanced selectivity and compounds that differ in structure and properties.…”

“…A primary motivation for such studies is that these species play an important role in the catalytic and chemisorption processes. [1][2][3][4][5][6][7][8][9][10][11][12][13] With these efforts, not only is the determination of the activity for certain chemical reactions available, but also the mechanism of heterogeneous catalysis concerning active sites of transition metals can be investigated. In recent years, synthesis and characterization of organic metal complexes containing carbonyl ligands have received considerable attention.…”

Organic molecules on zirconium surfaces

“…We should mention that there is a possibility of formation of a (1 ϫ1)-C structure as was observed for C 2 H 4 /Zr(0001), 16 but we did not perform LEED intensity analysis to verify this. We should mention that there is a possibility of formation of a (1 ϫ1)-C structure as was observed for C 2 H 4 /Zr(0001), 16 but we did not perform LEED intensity analysis to verify this.…”