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Photochromic Mechanism and Dual‐Phase Formation in Oxygen‐Containing Rare‐Earth Hydride Thin Films
Author(s) -
Hans Marcus,
Tran Tuan T.,
Aðalsteinsson Sigurbjörn M.,
Moldarev Dmitrii,
Moro Marcos V.,
Wolff Max,
Primetzhofer Daniel
Publication year - 2020
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202000822
Subject(s) - photochromism , materials science , hydride , gadolinium , hydrogen , transmission electron microscopy , thin film , phase (matter) , oxygen , photochemistry , yttrium , analytical chemistry (journal) , crystallography , nanotechnology , metallurgy , oxide , chemistry , organic chemistry , metal
The phase formation of a photochromic Gd 0.31 (H 0.55 O 0.45 ) 0.69 thin film, grown by reactive magnetron sputtering, is critically evaluated. Oxygen is preferably incorporated into the underdense columnar grain boundaries, when the as‐deposited gadolinium hydride film is exposed to ambient conditions. Two phases, Gd 2 O 3 and GdH 2 , are formed with significant compressive residual stress of 5.9 ± 1.5 GPa. These findings, extracted from transmission electron microscopy, X‐ray diffraction and atom probe tomography, provide a straightforward explanation for the photochromic effect. The mechanism can be understood as photon‐induced hydrogen transfer between the two phases, identical in nature to the photochromic effect in bulk yttrium hydride at high pressure.