Bimodal Plasmonic Color Filters Enable Direct Optical Imaging of Ion Implantation in Thin Films

Optical metamaterials offer precise control over the properties and interactions of light at the nanoscale, attracting interest in many new fields of research including chemical and molecular sensing, magnetic antennas, and photovoltaic elements. By utilizing the phenomenon of extraordinary optical transmission (EOT) plasmonic devices enable the detection of minute changes in the local, near-surface, dielectric properties of materials, opening up a wide range of different applications. Characterization of the optoelectronic properties of ultra-thin films is of paramount importance for a wide range of electronic applications including integrated circuit production. However, it is often extremely difficult to achieve using conventional imaging techniques. Here, it is demonstrated that plasmonic color filters can be used for the direct optical imaging and characterization of ion implantation in thin films. A model system consisting of variable doses of gallium ions implanted within titanium oxide thin films is used. It is observed that the ion implantation dose leads to a variation in the measured plasmon resonance spectra, which can be further enhanced through the use of bimodal nanopixel arrays. Using Monte Carlo simulations and the Maxwell-Garnett relation, the observed plasmon resonance spectra in terms of the gallium ion implantation dose is quantitatively interpreted.