Chugh Sunny, Mehta Ruchit, Man Mengren, Chen Zhihong
School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, United States.
Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, United States.
Sci Rep. 2016 Jul 27;6:30519. doi: 10.1038/srep30519.
Due to the small skin depth in metals at optical frequencies, their plasmonic response is strongly dictated by their surface properties. Copper (Cu) is one of the standard materials of choice for plasmonic applications, because of its high conductivity and CMOS compatibility. However, being a chemically active material, it gets easily oxidized when left in ambient environment, causing an inevitable degradation in its plasmonic resonance. Here, for the first time, we report a strong enhancement in the optical relaxation time in Cu by direct growth of few-layer graphene that is shown to act as an excellent passivation layer protecting Cu surface from any deterioration. Spectroscopic ellipsometry measurements reveal a 40-50% reduction in the total scattering rate in Cu itself, which is attributed to an improvement in its surface properties. We also study the impact of graphene quality and show that high quality graphene leads to an even larger improvement in electron scattering rate. These findings are expected to provide a big push towards graphene-protected Cu plasmonics.
由于在光学频率下金属中的趋肤深度较小，其等离子体激元响应很大程度上取决于其表面性质。铜（Cu）是等离子体激元应用的标准选择材料之一，因为它具有高导电性和与CMOS的兼容性。然而，作为一种化学活性材料，它在环境中放置时很容易被氧化，导致其等离子体共振不可避免地退化。在此，我们首次报道通过直接生长几层石墨烯，铜的光学弛豫时间得到了显著增强，该石墨烯被证明是一种出色的钝化层，可保护铜表面不发生任何劣化。光谱椭偏测量表明，铜自身的总散射率降低了40 - 50%，这归因于其表面性质的改善。我们还研究了石墨烯质量的影响，结果表明高质量的石墨烯会使电子散射率有更大的改善。这些发现有望大力推动石墨烯保护的铜等离子体激元学的发展。
