Subwavelength coatings and methods for making and using same
Methods are disclosed for forming subwavelength coatings for use in the UV, visible, or infrared part of the electromagnetic spectrum. A first material and a second material are deposited onto a substrate. The first material may include dielectric spheres of subwavelength size that self-assemble on the substrate to form a template or scaffold with subwavelength size voids between the spheres into which the second material is deposited or filled. First and second materials are heated on the substrate at a preselected temperature to form the subwavelength coating.
1. A method of forming a subwavelength plasmonic mesh coating, comprising the steps of:
depositing a first material comprising dielectric particles of a subwavelength size onto a substrate that self-assemble thereon forming a monolayer template with subwavelength voids between the dielectric particles;
etching the dielectric particles to reduce the size thereof and increase the size of the subwavelength voids between the dielectric particles in the monolayer template;
coating the monolayer template with a second material comprising a metal selected from Ag, Au, Al, or combinations thereof to substantially fill the subwavelength voids therein;
heating the monolayer template at a temperature from about 100° C. to about 300° C. for a time sufficient to sinter the second metal material therein forming a continuous and substantially periodic metal mesh between the dielectric particles in the subwavelength voids; and
removing the dielectric particles from the monolayer template to form the subwavelength plasmonic metal mesh coating on the substrate.
2. The method of claim 1 , wherein the substrate includes a glass, a ceramic, or a polymer.
3. The method of claim 1 , wherein depositing the first material includes delivering a liquid solution containing the dielectric particles with a delivery device positioned a selected distance above the surface of the substrate to obtain a substantially uniform coverage of the dielectric particles in the monolayer template.
4. The method of claim 1 , wherein coating the second material includes delivering a liquid solution containing the metal as metal particles of a selected size with a delivery device positioned a selected distance above the surface of the substrate.
5. The method of claim 1 , wherein coating the second metal material is performed via magnetron sputter deposition or thermal evaporation deposition.
6. The method of claim 1 , wherein coating the second material includes a second material comprising the metal and a material with a metal-insulator transition or a semiconductor.
7. The method of claim 1 , wherein the depositing and coating steps are performed with a roller-based coating method.
8. The method of claim 1 , wherein the dielectric particles are non-spherical.
9. The method of claim 1 , wherein the dielectric particles include a size selected from about 20 nm to about 500 nm such that the plasmonic metal mesh coating has a resonant absorption, reflection, or transmission with wavelengths of electromagnetic radiation in the UV, visible, or infrared spectrum.
10. The method of claim 1 , wherein the dielectric particles include a size selected from about 1 micron to about 15 microns such that the plasmonic metal mesh coating has a resonant absorption, reflection, or transmission with wavelengths of electromagnetic radiation in the infrared spectrum.