Fabrication of well-organized plasmonic interfaces by nanosphere lithography

Kasap, Yusuf
In this thesis, we propose to design plasmonic metal nanostructures by utilizing lithography with nanospheres of various diameters. When deposited at a high surface coverage, nanospheres form closed-pack trigonal lattices on surfaces, leaving concave triangular gaps in-between. After evaporation of thin metal films and lifting-off the nanospheres, metal islands which support plasmonic resonances and of the gap shape are fabricated in a trigonal periodicity on the substrate material. Depending on nanosphere diameter, the size of the triangular shaped nanostructures can be rearranged. In addition to classical nanosphere lithography (NSL) method, the physical influences that affect the fabrication method were also be considered in order to move beyond one step further. In other words, using annealing and physical etching mechanisms; size, shape of nanostructures and total surface coverage parameters were taken under control without deforming the system. Using these, our aim is to produce metal nanoparticle in desired shape and periodicity for plasmonic applications. Moreover, another goal is to prove that nanosphere lithography is a powerful tool especially for surface modification. In order to show that, how close-pack structure can be used is discussed by giving examples of different lithographic modifications. In this thesis work, we focus on experimental details of NSL and its extensions. After defining stages of production, we also show that NSL can be used to fabricate periodic metal structures with identical geometry and size, plasmonic interfaces with adjustable surface coverage, microlens arrays, and capability for generating 3D photonic crystals and adaptability with different lithography methods. In order to show them, we have used Scanning Electron Microscope (SEM), Raman Spectroscopy, total reflection techniques to characterize the nanostructures. Thanks to Comsol simulations and Gwyddion image analysis, experimental results are analyzed.