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MM: Fachverband Metall- und Materialphysik

MM 14: Functional Materials - Hydrogen

MM 14.6: Vortrag

Montag, 11. März 2013, 17:00–17:15, H26

Influence of hydrogen on Gd(0001) thin films — •Sara Wanjelik, Volkmar Heß, and Mathias Getzlaff — Institute of Applied Physics, University of Düsseldorf

Hydrogen in metals as an area of research has been of great interest for the past few decades. But only few investigations are carried out by imaging techniques with resolution on the nm-scale. Even less works deal with the inital stage of hydride formation.

Here we present STM measurements on thin Gadolinium films grown on a W(110) surface concentrating on the inital steps of hydrogen absorption. Due to the existence of a surface state only on the clean Gd(0001) surface, hydrogen covered areas appear lower in the topography image. Consequently, we can estimate the coverage and the time being necessary for absorption due to the reappearance of the surface state. Our measurements show that there is a lower limit for the amount of hydrogen to initiate the absorption process.

With increasing absorption hydride formation occurs. The larger volume of the hydride results in plastic deformations. On the one hand, there are disk-like islands with a diameter of approximately 3 nm and a height of 0.3 nm, while on the other hand there are coherent areas formed by ramps. The islands were found to arrange in chains. Therefore, we concentrate particularly on the direction of the chains being indicative for crystallographic properties inside the film.