Department of Physics, University of Texas at Austin , Austin, Texas 78712 United States.
Department of Physics, National Tsing-Hua University , Hsinchu 30013, Taiwan.
ACS Nano. 2016 Nov 22;10(11):9852-9860. doi: 10.1021/acsnano.6b05556. Epub 2016 Sep 23.
Aluminum (Al) provides an excellent material platform for plasmonic applications in the ultraviolet (UV) regime due to its low loss coefficient at UV wavelengths. To fully realize the potential of this material, it is imperative to create nanostructures with minimal defects in order to prevent light scattering and better support plasmonic resonances. In this work, we report the successful development of atomically smooth epitaxial Al films on silicon. These epitaxial Al thin films facilitate the creation of fine plasmonic nanostructures and demonstrate considerable loss reduction in the UV frequency range, in comparison to the polycrystalline Al films based on spectroscopic ellipsometry measurements. Remarkably, our measurements on the epitaxial Al film grown using the two-step method suggest that the intrinsic loss in Al is significantly lower, by up to a factor of 2 in the UV range, with respect to current widely quoted Palik's values extracted from polycrystalline films. These high-quality epitaxial Al films provide an ideal platform for UV plasmonics. In addition, the availability of intrinsic optical constants will enable more accurate theoretical predictions to guide the device design.
铝（Al）由于其在紫外（UV）波长下的低损耗系数，为 UV 区域的等离子体应用提供了极好的材料平台。为了充分发挥这种材料的潜力，必须制造出最小缺陷的纳米结构，以防止光散射并更好地支持等离子体共振。在这项工作中，我们报告了在硅上成功开发出原子级光滑的外延铝膜。这些外延 Al 薄膜有利于精细等离子体纳米结构的制造，并通过与基于光谱椭圆测量的多晶 Al 薄膜相比，在 UV 频率范围内显示出相当大的损耗降低。值得注意的是，我们对使用两步法生长的外延 Al 薄膜的测量表明，与从多晶薄膜中提取的当前广泛引用的 Palik 值相比，Al 的固有损耗在 UV 范围内显著降低，最高可达 2 倍。这些高质量的外延 Al 薄膜为 UV 等离子体学提供了理想的平台。此外，固有光学常数的可用性将能够进行更准确的理论预测，以指导器件设计。
