Structural and optical properties of MgxAl1-xHy gradient thin films: a combinatorial approach

Gremaud, Robin; Borgschulte, A.; Chacon, C.; Mechelen, J. L. M. van; Schreuders, H.; Züttel, Andreas; Hjörvarsson, B.; Dam, B.; Griessen, R.

doi:10.1007/s00339-006-3579-z

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Journal article

Structural and optical properties of Mg_xAl_1-xH_y gradient thin films: a combinatorial approach

Gremaud, Robin Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, Amsterdam, The Netherlands
Borgschulte, A. Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, Amsterdam, The Netherlands
Chacon, C. Department of Physics, Uppsala University, Sweden
Mechelen, J. L. M. van Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, Amsterdam, The Netherlands
Schreuders, H. Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, Amsterdam, The Netherlands
Züttel, Andreas Institut de Physique, Université de Fribourg, Switzerland
Hjörvarsson, B. Department of Physics, Uppsala University, Sweden
Dam, B. Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, Amsterdam, The Netherlands
Griessen, R. Department of Physics and Astronomy, Condensed Matter Physics, Vrije Universiteit, Amsterdam, The Netherlands

2006

Published in:

Applied Physics A. - 2006, vol. 84, no. 1-2, p. 77-85

English The structural, optical and dc electrical properties of Mg_xAl_1-x (0.2≤x≤0.9) gradient thin films covered with Pd/Mg are investigated before and after exposure to hydrogen. We use hydrogenography, a novel high-throughput optical technique, to map simultaneously all the hydride forming compositions and the kinetics thereof in the gradient thin film. Metallic Mg in the Mg_xAl_1-x layer undergoes a metal-to-semiconductor transition and MgH₂ is formed for all Mg fractions x investigated. The presence of an amorphous Mg-Al phase in the thin film phase diagram enhances strongly the kinetics of hydrogenation. In the Al-rich part of the film, a complex H-induced segregation of MgH₂ and Al occurs. This uncommon large-scale segregation is evidenced by metal and hydrogen profiling using Rutherford backscattering spectrometry and resonant nuclear analysis based on the reaction ¹H(¹⁵N,αγ)¹²C. Besides MgH₂, an additional semiconducting phase is found by electrical conductivity measurements around an atomic [Al]/[Mg] ratio of 2 (x=0.33). This suggests that the film is partially transformed into Mg(AlH₄)₂ at around this composition.

Faculty

Faculté des sciences et de médecine

Department

Département de Physique

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