Aliovalent Calcium Doping of Yttrium Oxyhydride Thin Films and Implications for Photochromism
Diana Chaykina (TU Delft - Applied Sciences)
Ismene Usman (TU Delft - Applied Sciences)
Giorgio Colombi (TU Delft - Applied Sciences)
Herman Schreuders (TU Delft - Applied Sciences)
Beata Tyburska-Pueschel (DIFFER – Dutch Institute for Fundamental Energy Research)
Ziying Wu (TU Delft - Applied Sciences)
Stephan W.H. Eijt (TU Delft - Applied Sciences)
Lars J. Bannenberg (TU Delft - RID/TS/Instrumenten groep, TU Delft - Applied Sciences)
Gilles A. De Wijs (Radboud Universiteit Nijmegen)
Bernard Dam (TU Delft - Applied Sciences)
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Abstract
To develop an understanding of the photochromic effect in rare-earth metal oxyhydride thin films (REH3-2xOx, here RE = Y), we explore the aliovalent doping of the RE cation. We prepared Ca-doped yttrium oxyhydride thin films ((CazY1-z)HxOy) by reactive magnetron cosputtering with Ca doping concentrations between 0 and 36 at. %. All of the films are semiconductors with a constant optical band gap for Ca content below 15%, while the band gap expands for compositions above 15%. Ca doping affects the photochromic properties, resulting in (1) a lower photochromic contrast, likely due to a lower H- concentration, and (2) a faster bleaching speed, caused by a higher pre-exponential factor. Overall, these results point to the importance of the H- concentration for the formation of a "darkened"phase and the local rearrangement of these H- for the kinetics of the process.
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