Structural Coloring of Glass Using Dewetted Nanoparticles and Ultrathin Films of Metals

Metal nanoparticles have been used for coloring glass since antiquity. Colors are produced by light scattering and absorption associated with plasmon resonances of the particles. Recently, dewetting at high temperature has been demonstrated as a straightforward high-yield/low-cost technique for nanopatterning thin metal films into planar arrays of spherical nanocaps. Here, we show that by simply tuning the contact angle of the metal dewetted nanocaps one can achieve narrow resonances and large tunability compared with traditional approaches such as changing particle size. A vast range of colors is obtained, covering the visible spectrum and readily controlled by the choice of film thickness and materials. The small size of the particles results in a mild dependence on incidence illumination angle, whereas their high anisotropy gives rise to strong dichroism. We also show color tuning through interference by simply adding an ultrathin metal film at a designated distance from the dewetted particle array. Our measurements are quantitatively well explained through analytical theory, which enables fast optimization of fabrication parameters. Good agreement between theory and experiment requires incorporating the effect of plasmon peak broadening caused by the finite size distribution of the particles. The proposed designs and techniques hold great potential for large-scale production of colored and dichroic glass with application to optical windows, filters, and displays.