Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 52: Topical session: In-situ Microscopy with Electrons, X-Rays and Scanning Probes in Materials Science VI - Structural transitions

MM 52.3: Vortrag

Donnerstag, 10. März 2016, 12:30–12:45, H38

Suppression of phase transformations in Nb-H thin films — •Vladimir Burlaka, Stefan Wagner, and Astrid Pundt — Universität Göttingen, Institut für Materialphysik, Friedrich-Hund-Platz 1, 37077 Göttingen

Mechanical stress in the GPa-range is known to arise during hydrogen absorption in metal films adhered to rigid substrates.[1] It can be released by plastic deformation. For thin films, stress release is much less efficient than for thicker films: It can be even suppressed, and very thin films can stay in a highly stressed state.[2] This influences the thermodynamic and kinetics properties of the system, and may suppress phase transformations.[3] In this presentation, we use Nb-H films as a model system to study the presence of phase transformations depending on the film thickness (d < 110 nm). Phase transformations can be monitored by studying surface corrugations with the scanning tunneling microscope (STM).[4] As soon as hydride precipitates form inside the metal film, a local height change will be detected in the film surface topography. We have demonstrated that this method is more sensitive than conventional XRD.[5] STM allows for finding a Nb-film thickness, below which no sign of a phase transformation can be found at 300K. Complementary methods support this experimental result. This research is kindly supported by the DFG via the projects PU131/12-1 and PU131/9-2. [1] A. Pundt et al. Annu. Rev. Mater. Res. 36 (2006) 555. [2] M. Hamm et al., APL 106 (2015) 243108. [3] S. Wagner et al., Int.J.Hydr.En., in print. [4] K. Nörthemann et. al., PRB 78 (2008) 014105. [5] V. Burlaka et al., JALCOM 645 (2015) 388.