Optical properties of oxygen-containing yttrium hydride thin films during and after the deposition

Abstract

The synthesis of the photochromic YHO films is based on the oxidation of deposited yttrium hydride in ambient conditions. The actual state of the films during the deposition process, which is influenced by the deposition pressure and the oxidation caused by the residual gases, is not completely known. We report on the YHxOy thin films deposited by reactive pulsed-DC magnetron sputtering. Since the visible light transmittance is closely related to the phase and chemical composition of the films, in-situ transmittance measurements during and after deposition are performed. Ex-situ spectroscopic ellipsometry is used to determine the optical constants of YHxOy throughout the film thickness. In order to obtain metallic YH2-x films, the densest possible structure with a high deposition rate is required, otherwise the films could already be partially transparent during the deposition. The transmittance is higher if deposition pressure is increased. This is because of the oxidation promoted by more porous growth of the microstructure that is observed at the surface and cross-section images of the films. The films exhibit a refractive index gradient perpendicular to the substrate surface, which is related to the porosity and variation of the chemical composition.

arXiv comment37 pages, 11 figures

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Cited by in corpus (5)

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• Role of hydrogen dynamics and deposition conditions in photochromic YHO/MoO${}_3$ bilayer films
• Growth-controlled photochromism in yttrium oxyhydride thin films deposited by HiPIMS and pulsed-DC magnetron sputtering
• Hydrogen partial pressure as a key parameter in the reactive sputtering of photochromic YHO thin films
• Substrate-controlled epitaxial-like growth of photochromic yttrium oxyhydride thin films