Preferential Orientation of Photochromic Gadolinium Oxyhydrides

28 May 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH2-x) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations, and photochromic response of the films are strongly dependent on the deposition pressure. GdHO films show preferential orientation along the [100] direction and exhibit photochromism when synthesized at deposition pressures up to 5.8 Pa and. The photochromic contrast is larger than 20 % when the films are deposited below 2.8 Pa with 0.22 H2/Ar flow ratio. We argue that the degree of preferential orientation defines the oxygen concentration which is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above are explained by the oxidation-induced decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas.

Keywords

Gadolinium oxyhydride
rare earth metal oxyhydride
mixed anion materials
photochromic effect
preferential orientation
band gap

Supplementary materials

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GdHO preferred orientation Supplementary chemrxiv
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