Berlin 2018 – scientific programme
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DS: Fachverband Dünne Schichten
DS 18: Optical Analysis of Thin Films (Reflection, Ellipsometry, Raman, IR-DUV Spectroscopy, ...): Session I
DS 18.6: Talk
Wednesday, March 14, 2018, 11:15–11:30, H 0111
In-situ Monitoring of Lateral Hydrogen Diffusion in Amorphous and Polycrystalline Tungsten Trioxide Thin Films — •Simon Burkhardt1,2, Matthias T. Elm1,2,3, Bernhard Lani-Wayda4, and Peter J. Klar1,2 — 1Institute of Experimental Physics I, Heinrich-Buff-Ring 16, 35392 Gießen, Germany — 2Center for Materials Research (LaMa), Heinrich-Buff-Ring 16, 35392 Gießen, Germany — 3Institute of Physical Chemistry, Heinrich-Buff-Ring 17, 35392 Gießen, Germany — 4Mathematical Institute, Arndtstrasse 2, 35392 Gießen, Germany
Tungsten trioxide (WO3) thin films show remarkable changes of their optical properties upon reversible ion insertion making them essential components in electrochromic devices. The development of such devices demands a fundamental understanding of charge carrier transport in WO3. In-situ transmission spectroscopy during locally confined electrochemical hydrogen insertion is used to investigate the lateral diffusion of hydrogen inside amorphous and polycrystalline WO3 thin films. The absorbance of WO3 thin films is resolved spatially and temporally at a wavelength of (637 ± 15) nm. The results reveal concentration-dependent diffusion processes in both, amorphous and polycrystalline WO3. By comparing experimental data with numerical simulations, the dependence of the diffusion coefficient on the hydrogen concentration is investigated. Although amorphous WO3 thin films are known for their faster coloration kinetics, the diffusivity of hydrogen in polycrystalline WO3 is found to exceed the diffusivity of hydrogen in amorphous WO3.