Al Shakhs Mohammed, Augusto Lucian, Markley Loïc, Chau Kenneth J
School of Engineering, The University of British Columbia, Kelowna, British Columbia, Canada.
Sci Rep. 2016 Feb 10;6:20659. doi: 10.1038/srep20659.
We propose a hypothesis that a very thin layer can be made more transparent by adding a thin coating with susceptibility of opposing sign. Two experimental tests backed by a theoretical model support this hypothesis. First, we show that the visible and near-infrared transmission through a semi-transparent silver film can be enhanced by up to ~70% and spectrally tailored depending on the type and thickness of the dielectric coating. Material types explored as dielectric coating layers include conventional metal oxides (titanium dioxide) and lesser-explored elemental semiconductors (undoped silicon, p-type silicon, and germanium). Second, and more surprisingly, we show that coating a 50-nm-thick silicon nitride membrane with a 10-nm-thick silver layer can modestly enhance the transmission by up to 6 ± 1% in the blue part of the spectrum. Transmission enhancements are observed for three silver-coated membranes in different configurations. Thinner silver coatings are theoretically capable of enhancement factors greater than 10%, but implementation is restricted by challenges in making smooth and continuous silver films below 10 nm in thickness. This study is important because it is the first demonstration of reciprocity with respect to the transmission enhancements achieved by combining thin metallic and dielectric layers.
我们提出一个假设，即通过添加具有相反符号磁化率的薄涂层，可以使非常薄的层变得更加透明。由理论模型支持的两项实验测试证实了这一假设。首先，我们表明，通过半透明银膜的可见光和近红外透射率可以提高约70%，并且根据介电涂层的类型和厚度进行光谱调整。作为介电涂层探索的材料类型包括传统金属氧化物（二氧化钛）和研究较少的元素半导体（未掺杂硅、p型硅和锗）。其次，更令人惊讶的是，我们表明，用10纳米厚的银层涂覆50纳米厚的氮化硅膜，在光谱的蓝色部分可以适度提高透射率，最高可达6±1%。在不同配置下对三个银涂层膜观察到了透射增强。理论上，更薄的银涂层能够实现大于10%的增强因子，但由于制备厚度低于10纳米的光滑连续银膜存在挑战，其实施受到限制。这项研究很重要，因为它首次证明了关于通过组合薄金属层和介电层实现的透射增强的互易性。
