Abstract
Alloyed metals in nanoscale exhibit some intriguing features that are absent in mono-metallic nanostructures. Here we report silver and gold alloyed nanoislands with high tunability of localized surface plasmon resonance (LSPR) wavelength in the visible range for wafer-level plasmonic color filter arrays. The nanofabrication includes two simple steps of concurrent thermal evaporation of Ag and Au grains and solid-state dewetting of the as-deposited nanocomposite thin film. The alloy ratio during the evaporation precisely tunes the LSPR wavelengths within 415–609 nm spectrum range. The elemental composition map reveals that alloyed nanoislands are completely miscible while preserving uniform size, regardless of the alloy ratio. Besides, the multiple lift-off processes and thermal dewetting of Ag/Au nanocomposite thin films successfully demonstrate the wafer-level nanofabrication of plasmonic color filter mosaic. Each plasmonic color pixel comprises different alloy ratio and efficiently transmits colors ranging from cyan, yellow, and magenta. The transmission spectra transposed onto a CIE 1931 color map show comparable color diversity to the plasmonic color filters fabricated by conventional e-beam lithographic techniques. This novel method provides a new direction for large-scale and visible plasmonic color filter arrays in advanced display or imaging applications.
Highlights
Geometric dimensions and elemental compositions of metal nanostructure mainly determine the plasmon resonance wavelength[21,22]
Alloyed nanostructures for broad band tuning of localized surface plasmon resonance (LSPR) wavelength with versatile nanofabrication still remain an unsolved task for plasmonic color filter array applications
Noble metals Ag and Au are selected to feature LSPR wavelengths in the both far ends of the visible spectrum according to the dispersion relation
Summary
The LSPR wavelength of nanoislands becomes red-shifted from [415, 427, 449, 494, 526, 547] to 609 nm, for increasing Au alloy ratio of Ag, Au10Ag90, Au30Ag70, Au50Ag50, Au70Ag30 Au90Ag10, and Au, respectively This is in accordance to the back-scattered color images, captured using a dark-field mode microscope (Nikon, L-IM). The substrate was thermally dewetted inside box furnace for 60 minutes at 500 °C to fabricate wafer-level plasmonic color filter arrays. This work successfully demonstrated Ag/Au alloyed nanoislands for large-area plasmonic color filter arrays using concurrent thermal evaporation and solid-state dewetting. The LSPR wavelengths of the alloyed substrates is effectively controlled from 415 to 609 nm range by adjusting the Au ratio, which in response generates scattered RGB mode or transmitted CYM color sets. This novel wafer-level plasmonic arrays of alloyed nanoislands provide new outlooks for advanced display or imaging applications
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