Yttrium oxyhydride (YHO) is a rare‐earth‐metal oxyhydride that has attracted considerable attention due to its outstanding photochromic properties. The transparency of YHO thin films across the infrared and visible spectral regions is reduced considerably under UV illumination (photodarkening) and recovers when the illumination is removed (bleaching). Although oxygen diffusion has been shown to be necessary for these processes, the exact mechanism for the photochromic behavior is not yet understood. In this work, infrared spectroscopy is utilized to investigate the effect of temperature on the photochromic properties of YHO thin films. The measurements show that YHO can photodarken at temperatures as low as 5 K, where anion diffusion is expected to be severely limited. The bleaching of the films is small, but not zero, for temperatures between 5 and 50 K. A stepwise recovery of the transmittance is observed as the temperature of the films is increased above 100 K up to 250 K. The temperature‐dependent data show that anion diffusion is not required to explain the photochromic behavior of YHO, and that an additional mechanism (or mechanisms), e.g., electronic charge transfer, contributes to the photochromic behavior of YHO, as well as other rare‐earth‐metal oxyhydrides.

中文翻译：

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氢氧化钇薄膜的温度依赖性光致变色性能

氢氧化钇（YHO）是一种稀土金属氢氧化盐，由于其出色的光致变色特性而备受关注。YHO薄膜在红外和可见光谱区域的透明性在UV照射下（光暗化）显着降低，并在去除照射（漂白）后恢复。尽管已经证明氧扩散对于这些过程是必需的，但是对于光致变色行为的确切机理尚不清楚。在这项工作中，利用红外光谱来研究温度对YHO薄膜光致变色特性的影响。测量结果表明，YHO在低至5 K的温度下会发生光暗化，预计阴离子的扩散将受到严重限制。薄膜的漂白很小，但不为零，