Vibrational enhancement in the dynamics of ammonia dissociative chemisorption on Ru(0001)

The work function changes of vacuum deposited molybdenum films caused by the chemisorption of propylene, acetylene, hydrogen and nitrogen were measured using the Kelvin vibrating capacitor method. During the hydrocarbon chemisorption, the work function increased in a low surface coverage region but decreased at the higher surface coverages. The saturation values of the work function changes corresponding to complete coverage of the surface by chemisorbed propylene and acetylene equal -0.08 eV and -0.42 eV, respectively. The observed dependences of the work function change on surface coverage are interpreted by the dissociative chemisorption of hydrocarbons on a limited number of surface sites which are simultaneously the sites of preferred adsorption. The extent of dissociation decreases in the adsorption with the increasing surface coverage. The results of the study of the work function changes induced by the hydrogen and nitrogen chemisorption enabled to draw several conclusions on the surface topography of the used films.

Download Full-text

Adsorption of carbon monoxide on the iridium fcc (112) surface: Topological study

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19890566 ◽

1989 ◽

Vol 54 (3) ◽

pp. 566-571 ◽

Cited By ~ 1

Author(s):

Jiří Pancíř ◽

Ivana Haslingerová

Keyword(s):

Carbon Monoxide ◽

Topological Method ◽

Dissociative Chemisorption ◽

Semi Empirical

A semi-empirical topological method was applied to a study of an Ir(112) surface as well as to both a nondissociative and dissociative chemisorption on this surface. In all cases studied an attachment of carbon to the surface is energetically more favorable than an attachment of oxygen. The preferential capture of the CO molecule on atop sites is remarkable. The capture on n-fold hollow positions as well as the dissociative chemisorption of carbon monoxide on the Ir(112) surface are energetically prohibited.

Download Full-text

A topological quantum-chemical study of the chemisorption of carbon monoxide on the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19901907 ◽

1990 ◽

Vol 55 (8) ◽

pp. 1907-1919

Author(s):

Jiří Pancíř ◽

Ivana Haslingerová

Keyword(s):

Carbon Monoxide ◽

Quantum Chemical ◽

Co Adsorption ◽

Quantum Chemical Study ◽

Chemical Study ◽

Dissociative Chemisorption ◽

Frontier Orbitals ◽

Surface Sites ◽

Charged Surfaces ◽

Topological Quantum

A semiempirical quantum-chemical topological method is applied to the study of the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir and the nondissociative as well as dissociative chemisorption of carbon monoxide on them. On Ni, dissociative chemisorption is preferred to linear capture, whereas on Pd and Pt, linear capture is preferred although dissociative chemisorption is also feasible. On Rh and, in particular, on Ir, dissociative chemisorption is energetically prohibited. The high dissociative ability of the Ni surface can be ascribed to a rather unusual charge alteration and to the degeneracy of the frontier orbitals. Negative charges at the surface level are only found on the Ni and Pt surfaces whereas concentration of positive charges is established on the Rh and Ir surfaces; the Pd surface is nearly uncharged. Metals with negatively charged surfaces seem to be able to dissociate molecules of carbon monoxide. It is demonstrated that CO adsorption can take place on all metal surface sites, most effectively in the valley of the step. In all the cases studied, the attachment to the surface is found to be energetically more favourable for the carbon than for the oxygen.

Download Full-text

Quantification of multilayer-induced dissociative chemisorption: cyclobutane on Ru(001)

Surface Science ◽

10.1016/s0039-6028(99)00220-4 ◽

1999 ◽

Vol 426 (2) ◽

pp. 154-162 ◽

Cited By ~ 2

Author(s):

Michael J Weiss ◽

Christopher J Hagedorn ◽

W.Henry Weinberg

Keyword(s):

Dissociative Chemisorption

Download Full-text

Atomically Smooth Ultrathin Oxide Layers on SI(113)

MRS Proceedings ◽

10.1557/proc-567-169 ◽

1999 ◽

Vol 567 ◽

Cited By ~ 2

Author(s):

H.-J. Müssig ◽

J. Dabrowski ◽

S. Hinrich

Keyword(s):

Elevated Temperatures ◽

Oxidation Mechanism ◽

Dissociative Chemisorption ◽

Initial Oxidation ◽

Precursor State ◽

Oxide Layers ◽

Adsorption Sites ◽

Molecular Precursor ◽

Diffusion Paths ◽

Ultrathin Oxide

ABSTRACTWe report the first direct observation of dissociative chemisorption of oxygen molecules on a silicon surface at room temperature via a molecular precursor state. We link this to the fact that smooth oxide layers can be grown easily on Si(113). The process of initial oxidation is discussed in terms of surface diffusion paths and surface stress. First ab initiocalculations help elucidate the favored adsorption sites and the oxidation mechanism. Experimental evidence was found for bond geometries resulting in the quasi-epitaxial growth of a chemisorption layer on the substrate at elevated temperatures (600°C). In contrast to the first stages of Si(001) oxidation, neither defects nor the ejection of Si atoms plays a significant role during the initial oxidation of Si(113).

Download Full-text