Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.22: Poster

Monday, March 27, 2006, 18:00–21:00, P2

Adsorption and dissociation studies of acetylene on steel — •Hesna Hülya Yildiz Ünveren, Reinhard Denecke, and Hans-Peter Steinrück — Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen

Normal steel can be turned into high performance (hard and wear resistant) material by low-pressure carburization. In this process, carbon atoms from dissociation of hydrocarbons diffuse into the surface layer of the steel.

In order to gain a more detailed understanding of this surface process, adsorption and dissociation of acetylene on steel have been investigated utilizing molecular beam techniques and Auger electron spectroscopy. Sticking probabilities were measured by the technique of King and Wells for different surface temperatures between 100 and 950 K and varying kinetic energy of the acetylene molecules, using controlled sample conditions. While no or very small adsorption of acetylene was observed for low kinetic energies of the molecules (~90 meV) at surface temperatures below 800 K, a significant reactive sticking coefficient of approx. 10 % could be found at 900 K. In a second step the kinetic energy of the molecules is increased (by seeding) to enable dissociation at lower substrate temperatures where no diffusion occurs. By combination of the results, the dissociation step and the diffusion of carbon into the bulk can be disentangled.

This work is supported by BMBF (03X2506C).