论文标题
混合和退火对tio $ _ {2} $的光学和机械性能的影响：ta $ _ {2} $ o $ $ _ {5} $无定形涂料
Effects of mixing and annealing on the optical and mechanical properties of TiO$_{2}$:Ta$_{2}$O$_{5}$ amorphous coatings
论文作者
论文摘要
无定形混合钛 - 坦塔拉涂层是重力波探测器（GWDS）中Bragg反射器的关键组成部分。对于GWDS，达到涂料中光吸收和机械损失的最低值是至关重要的，这需要对涂层沉积和沉积后退火进行复杂的优化。我们在这里介绍了对离子束溅射生长的无定形混合钛tantala涂层的光学特性和内部摩擦的系统研究。我们考虑具有六种不同阳离子混合比的涂层，并以备注状态和退火状态研究它们。通过利用光谱椭圆法数据和建模，以及辅助技术，我们检索了涂料的介电函数。在改变混合比并进行退火时，我们会发现上述大多数特性的单调趋势。重制，解放后的URBACH能量对混合比的最小值约为20％，非常接近显示GWDS应用的最低光学吸收的涂料的组成。我们建议在URBACH能量中观察到的最小值不仅取决于混合比，还取决于退火参数。另一方面，发现最小涂层损耗角度依赖于所考虑的测量频率，并位于相当广泛的Ti含量范围内，这表明在研究后沉积后退火后寻找绝对最小值的搜索应在研究最佳退火参数的研究中寻求。这项工作构成了无定形混合钛 - 坦塔拉涂层的光学特性的参考，并突出了urbach能量在优化材料的优化过程中的相关性。
Amorphous mixed titania-tantala coatings are key components of Bragg reflectors in the gravitational wave detectors (GWDs). Attaining the lowest possible values of optical absorption and mechanical losses in the coatings is of paramount importance for GWDs, and this requires a complex optimization of the coating deposition and post-deposition annealing. We present here a systematic investigation of the optical properties and internal friction of amorphous mixed titania-tantala coatings grown by ion beam sputtering. We consider coatings with six different cation mixing ratios and we study them both in the as-deposited and annealed state. By exploiting spectroscopic ellipsometry data and modelling, along with ancillary techniques, we retrieved the dielectric function of the coatings in a wide spectral range. When varying the mixing ratio and performing the annealing we find monotonic trends for most of the aforementioned properties. Remakably, the post-annealing Urbach energy displays a definite minimum for a mixing ratio around 20%, very close to the composition of the coatings showing the lowest optical absorption for GWDs applications. We suggest that the observed minimum in the Urbach energy depends not only on the mixing ratio, but also on the annealing parameters. On the other hand, the minimum coating loss angle was found to be weakly dependent on the considered measurement frequency and to lie within a rather broad range of Ti content, suggesting that the search for an absolute minimum following post-deposition annealing should be rather sought in the study of the best annealing parameters for each specific cation ratio considered. This work constitutes a reference for the optical properties of the amorphous mixed titania-tantala coatings, and highlights the relevance of the Urbach energy in the optimization process of materials for high-performing Bragg reflectors.
