Lithography-free fabrication and optical characterizations of nanotextured nickel dewetting thin film for broadband absorbers

Abstract

Plasmonic structures based on metamaterials are widely studied and have been extensively researched in various applications. However, the fabrication of regular nanostructures always requires expensive equipment and a strict working environment, lacking the ability for large-scale fabrication. In this study, we propose and demonstrate simple nanotextured nickel (Ni) dewetting thin films on silicon (Si) and quartz substrates by using different thermal annealing temperatures. They achieve a broadband absorption range with near zero reflectivity due to the standing-wave resonances of surface plasmon polariton, and the resonance is relative to the material of the substrate. The topographies of the nanotextured Ni dewetting thin films vary with thermal annealing temperatures at different dewetting stages. The corresponding reflection and absorption resonant wavelengths of the devices are redshifted by increasing the thermal annealing temperatures. The main absorption resonances are at wavelengths of 610 nm, 580 nm, 625 nm, and 660 nm on the Si substrate. While the reflectivity of the sample around the visible range is lower than 40%, it is suitable for broadband absorption for green and yellow spectra. Moreover, the resonant wavelengths are blueshifted by increasing the incident angles. The demonstrated devices are also sensitive to the ambient media. The reflection resonant wavelengths are redshifted by increasing the environmental refraction indexes. The corresponding reflected colors are changed from green to yellow . These devices exhibit a highest sensitivity of 500 nm RIU−1 and can be used for color sensors. This proposed approach has large-scale fabrication capacity and provides promising applications for broadband absorbers, reflective displays, environmental sensors, and other optoelectronic fields.