Gate Tunable Plasmonic Color Filter Based on Transition Metal Nitride Heterostructures

Meng-Ju Yu^1*, Kuan-Wei Lee¹, Yu-Jung Lu^1,2

¹Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
²Department of Physics, National Taiwan University, Taipei, Taiwan

* Presenter:Meng-Ju Yu, email:sunnymeng@gate.sinica.edu.tw

Modifying efficiency and enhancing color resolution by tuning nanostructured geometry and structure have been an active area of research during last decade due to number of interesting potential applications in image sensor, photovoltaic harvesting, super-pixel display. Here, we report reflection rate modification of the multi-layer metal-dielectric-metal nanostructures based on plasmonic resonance. Namely, using tunable aperture array geometry realizes photon-plasmon interaction efficiently at specific resonance wavelengths and demonstrates the capable of filtering white light into individual colors across the visible range. We use rf sputtering to fabricate transition nitride film, such as Titanium Nitride and Zirconium Nitride, as the active layer. By changing sputtering parameters, for instance, the flow ratio of Ar to nitrogen and growth temperature, we control the carrier concentration, and, hence, complex refractive index in films.
In order to design the tunable plasmonic color filter, we use finite-differenece time-domain (FDTD) to simulate the optical transmission, reflectance, electric field intensity and magnetic field intensity. Next, by using sputtering and lithographic techniques, we experimentally fabricate multiple plasmonic heterostructures nanoresonator that have identical geometry but different carrier concentrations. The studied tunable plasmonic color filters consist of a metal-dielectric-metal corresponding to TiN/SiO₂/Ag in each layer. The top TiN layer is used to control refractive index and carrier concentration (9×10²¹-5×10²² cm^-3) by tuning gate voltage. Thus, the plasmon resonant frequency can be tuned. We will discuss the functionality of color tunability and the practical applications.

Keywords: plasmonics, titanium nitride , gate tunable, heterostructure, color filter