It has been recently revealed that strontium titanate (${\mathrm{SrTiO}}_3$) displays persistent photoconductivity with unique characteristics: it occurs at room temperature and lasts over a very long period of time. Illumination of ${\mathrm{SrTiO}}_3$ crystals at room temperature with sub-band-gap light reduces the electrical resistance by three orders of magnitude and persists for weeks or longer [Tarun et al., Phys. Rev. Lett. 111, 187403 (2013)]. Experiments indicate that oxygen vacancy and hydrogen play important roles, yet the microscopic mechanism responsible for this remarkable effect has remained unidentified. Using hybrid density functional theory calculations we show that an instability associated with substitutional hydrogen ${\mathrm{H}}_{\mathrm{O}}^{+}$ under illumination, which becomes doubly ionized and leaves the oxygen site, can explain the experimental observations. ${\mathrm{H}}_{\mathrm{O}}$ then turns into an interstitial hydrogen and an oxygen vacancy, leading to excess carriers in the conduction band. This phenomenon is not exclusive to ${\mathrm{SrTiO}}_3$, but it is also predicted to occur in other oxides. Interestingly, this phenomenon represents an elegant way of proving the existence of hydrogen substituting on an oxygen site (${\mathrm{H}}_{\mathrm{O}}$), forming an interesting, and rarely observed, type of three-center, two-electron bond.

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SrTiO3及相关材料中持久保持室温持久的光电导性的原因

最近发现，钛酸锶（${\mathrm{钛酸锶}}_3$）表现出具有独特特征的持久光电导性：它发生在室温下，并且持续很长时间。照明${\mathrm{钛酸锶}}_3$室温下具有亚带隙光的晶体将电阻降低了三个数量级，并持续了数周或更长时间[Tarun等。，物理 牧师 111，187403（2013）]。实验表明，氧空位和氢起着重要的作用，但是导致这种显着影响的微观机制仍不清楚。使用混合密度泛函理论计算，我们表明与氢取代相关的不稳定性${\mathrm{H}}_{\mathrm{Ø}}^{+}$ 在双倍离子化并离开氧气位置的光照下，可以解释实验观察。 ${\mathrm{H}}_{\mathrm{Ø}}$然后变成间隙氢和氧空位，导致导带中的载流子过多。这种现象不仅仅限于${\mathrm{钛酸锶}}_3$，但也预计会在其他氧化物中发生。有趣的是，这种现象代表了一种优雅的方式来证明氢在氧气位点上的存在（${\mathrm{H}}_{\mathrm{Ø}}$），形成一个有趣的，很少见的三中心，两个电子键的类型。