Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Ave., Boston, MA 02115, United States of America.
Nanotechnology. 2019 Jan 4;30(1):015202. doi: 10.1088/1361-6528/aae756. Epub 2018 Oct 29.
Single and few-layer graphene flakes, while visible on a dielectric surface with customized thickness, cannot be optically imaged when exfoliated directly on semiconductors or metal substrates with arbitrary thickness. In this paper, we show that such graphene flakes become visible through a conventional microscope on a substrate patterned with a submicron sized, hexagonally packed array of gold disks. The interaction of the metal pattern with the incident light generates surface plasmon polaritons (SPPs) and results in enhanced reflectivity for certain angles and wavelengths. In the areas where graphene flakes are present, the interaction of the SPP with incident radiation is altered and consequently decreases the reflectivity in this region and increases the contrast, which accounts for the visibility of the graphene flakes on such substrates. We validate the observed contrast in visibility utilizing an in-house developed modified form of rigorous coupled wave analysis algorithm to appropriately incorporate the optical properties of two-dimensional materials. We present a parametric study of the contrast of graphene flakes on the patterned substrate to demonstrate the robustness of the visibility.
单层和少数层石墨烯片在具有定制厚度的介电表面上可见，但当直接在具有任意厚度的半导体或金属衬底上剥落时，无法通过光学成像观察到。在本文中，我们表明，通过在衬底上形成亚微米尺寸、六边形排列的金盘阵列，可以使这种石墨烯片在常规显微镜下可见。金属图案与入射光的相互作用产生表面等离激元（SPP），并导致在某些角度和波长下反射率增强。在存在石墨烯片的区域，SPP 与入射辐射的相互作用发生改变，从而降低该区域的反射率并增加对比度，这解释了在这种衬底上石墨烯片的可见性。我们利用内部开发的严格耦合波分析算法的改进形式来验证所观察到的对比度，以适当纳入二维材料的光学性质。我们对图案化衬底上石墨烯片对比度进行参数研究，以证明其可见度的稳健性。
