SrTiO₃ is the model perovskite compound and has demonstrated technological relevance from being the foundation of oxide electronics to a promising candidate as a high-temperature hydrogen sensor. Here, we fully investigate the temperature-dependent UV-Vis optical constants of pristine and doped SrTiO₃ in the spectral range 0.73-5.90 eV using spectroscopic ellipsometry and first-principles. The oscillator model is applied to analyze and quantify the temperature and doping effect. After heating SrTiO₃ from 300 to 873 K, the amplitude of the dominant absorption peak at 4.752 eV is reduced by 11% and the shoulder of optical spectrum at 3.708 eV gradually disappears. By doping SrTiO₃ with Nb element from 0.05 to 0.7% wt, extra momentum is provided to enable indirect absorption and an unconventional Urbach tail is observed due to the increased crystalline disorder. Moreover, the first-principles calculations considering the many-body excitonic effect and phonon-assisted indirect absorption are performed, which help to determine the physics origin of absorption peaks and explain the temperature influence. This work sheds light on temperature and doping dependence of UV-Vis dielectric functions of cubic SrTiO₃, aiming to elucidate the novel fundamental optical phenomena of SrTiO₃-based heterostructures or devices.

中文翻译：

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立方SrTiO _3的掺杂和温度相关的UV-Vis光学常数：椭圆偏振光谱和第一性原理的组合研究

SrTiO ₃是钙钛矿型化合物，已证明其技术实用性，从作为氧化物电子学的基础到作为高温氢传感器的有前途的候选者。在这里，我们使用椭圆偏振光谱法和第一性原理充分研究了原始温度和掺杂SrTiO ₃在0.73-5.90 eV光谱范围内随温度变化的UV-Vis光学常数。振荡器模型用于分析和量化温度和掺杂效应。在将SrTiO ₃从300加热到873 K之后，在4.752 eV处的主要吸收峰的幅度减小了11％，而在3.708 eV处的光谱肩逐渐消失了。通过掺杂SrTiO ₃当Nb元素含量为0.05％至0.7％wt时，可提供额外的动量以实现间接吸收，并且由于增加的晶体紊乱而观察到非常规的Urbach尾巴。此外，进行了考虑多体激子效应和声子辅助间接吸收的第一性原理计算，这有助于确定吸收峰的物理起源并解释温度的影响。这项工作揭示了立方SrTiO _3的温度和UV-Vis介电功能的掺杂依赖性，旨在阐明基于SrTiO ₃的异质结构或器件的新型基本光学现象。