Regensburg 2007 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 15: Poster Session

DS 15.66: Poster

Dienstag, 27. März 2007, 15:00–17:00, Poster B

Study of the carbon dioxide adsorption on silicon — •Daniela Lietz, Michael Paulus, Christian Sternemann, and Metin Tolan — Exp. Physics E1a/DELTA, University Dortmund

In order to investigate the adsorption of carbon dioxide on a silicon wafer, the layer thickness and roughness are determined in dependence of the CO₂−pressure via X-ray reflectivity. Due to the use of a high pressure cell the experiment has been accomplished at a photon energy of 27 keV at BL9 of the synchrotron radiation source DELTA. In order to observe different degrees of adsorption, the gas pressure was increased in 17 steps from 0 bar to 34.4 bar (near condensation pressure of CO₂). For each pressure step an X-ray reflectivity was recorded. The measured reflectivities are refined with the use of the effective density model. The layers thickness, roughness and dispersion were determined. The adsorption isotherm (layer thickness vs. pressure) shows the anticipated increase of layer thickness with rising pressure. From the adsorption isotherm the Hamaker constant was determined in order to qualify the amplitude of the interaction between substrate and layer on a microscopic scale. The roughness shows an increase with the thickness which is due to the interaction between the substrate and the surface which smoothes the layers surface especially at low layer thickness.