Influence of Cation (RE = Sc, Y, Gd) and O/H Anion Ratio on the Photochromic Properties of REO x H3-2 x Thin Films

Giorgio Colombi; Tom De Krom; Diana Chaykina; Steffen Cornelius; Stephan W H Eijt; Bernard Dam

doi:10.1021/acsphotonics.0c01877

Influence of Cation (RE = Sc, Y, Gd) and O/H Anion Ratio on the Photochromic Properties of REO _x H_{3-2 x} Thin Films

ACS Photonics. 2021 Mar 17;8(3):709-715. doi: 10.1021/acsphotonics.0c01877. Epub 2021 Feb 16.

Authors

Giorgio Colombi¹, Tom De Krom², Diana Chaykina^{1

2}, Steffen Cornelius^{1

3}, Stephan W H Eijt², Bernard Dam¹

Affiliations

¹ Materials for Energy Conversion and Storage, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, NL-2629HZ Delft, The Netherlands.
² Fundamental Aspects of Materials and Energy, Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft, The Netherlands.
³ Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (FEP), Winterbergstrasse 28, 01277 Dresden, Germany.

Abstract

Rare-earth oxyhydride REO _x H_3-2x thin films prepared by air-oxidation of reactively sputtered REH₂ dihydrides show a color-neutral, reversible photochromic effect at ambient conditions. The present work shows that the O/H anion ratio, as well as the choice of the cation, allow to largely tune the extent of the optical change and its speed. The bleaching time, in particular, can be reduced by an order of magnitude by increasing the O/H ratio, indirectly defined by the deposition pressure of the parent REH₂. The influence of the cation (RE = Sc, Y, Gd) under comparable deposition conditions is discussed. Our data suggest that REs of a larger ionic radius form oxyhydrides with a larger optical contrast and faster bleaching speed, hinting to a dependency of the photochromic mechanism on the anion site-hopping.