Nanopillar-based articles and methods of manufacture
Nanopillar-based THz metamaterials, such as split ring resonator (SRR) MMs, utilizing displacement current in the dielectric medium between nanopillars that significantly increases energy storage in the MMs, leading to enhanced Q-factor. A metallic nanopillar array is designed in the form of a single gap (C-shape) SRR. Vacuum or dielectric materials of different permittivities are filled between the nanopillars to form nanoscale dielectric gaps. In other embodiments, formation of patterned nanowires using anodic aluminum oxide (AAO) templates with porous structures of different heights resulting from an initial step difference made by etching the aluminum (Al) thin film with a photoresist developer prior to the anodization process are disclosed.
1. A terahertz metamaterial device comprising:
a substrate;
a conductive pattern formed on the substrate, the conductive pattern comprising a multiplicity of nanopillars;
wherein the conductive pattern comprises a split ring resonator.
2. The terahertz metamaterial device of claim 1 , wherein each of the nanopillars comprises a cross-sectional shape selected from the group consisting of a circle and a polygon.
3. The terahertz metamaterial of claim 1 , wherein the nanopillars of the multiplicity of nanopillars are respectively formed of an electrically conductive material, and further wherein the substrate is formed of an electrically insulative material, and further wherein the nanopillars contact and extend directly from the substrate.
4. The terahertz metamaterial device of claim 1 , wherein the split ring resonator is a single gap C-shape split ring resonator.
5. The terahertz metamaterial device of claim 1 , wherein immediately adjacent ones of the nanopillars of the multiplicity of nanopillars of the split ring resonator are separated by a respective nanogap.
6. The terahertz metamaterial device of claim 5 , wherein the size of each of the respective nanogaps is in the range of 1 to 40 nanometers.
7. The terahertz metamaterial of claim 5 , wherein a size of each of the nanogaps is selected such that when electromagnetic waves are applied to the nanopillars, a transient electric field is induced between the nanopillars.
8. The terahertz metamaterial device of claim 1 , wherein each of the nanopillars of the multiplicity of nanopillars comprises an electrically conductive metal.
9. The terahertz metamaterial device of claim 8 , wherein the electrically conductive metal of each of the nanopillars is selected from the group consisting of gold and platinum.
10. The terahertz metamaterial device of claim 1 , wherein the split ring resonator has a Q-factor of at least 300.
11. The terahertz metamaterial device of claim 1 , wherein the conductive pattern further comprises a plurality of split ring resonators.
12. The terahertz metamaterial device of claim 1 , wherein the terahertz metamaterial device is a sensor selected from the group consisting of a chemical sensor, a biological sensor, a temperature sensor, a strain sensor and a positioning sensor.
13. A method of making a terahertz metamaterial device, the method comprising:
forming a multiplicity of nanopillars on a substrate;
wherein the nanopillars combine to define a conductive pattern;
wherein the conductive pattern includes a split ring resonator.
14. The method of claim 13 , wherein immediate adjacent ones of the nanopillars of the multiplicity of nanopillars of the split ring resonator pattern are separated by a respective nanogap.
15. The method of claim 13 , wherein the step of forming a multiplicity of nanopillars includes forming a template on the substrate.
16. The method of claim 15 , wherein the step of forming a template includes:
forming a metal layer on the substrate;
coating an outer surface of the metal layer with a resist layer;
applying a developer to develop a pattern in the resist layer, including the developer partially etching a region of the metal layer corresponding to the pattern;
removing the resist layer; and
after the step of removing the resist layer, anodizing the metal layer to form porous structures in the metal layer, wherein the porous structures formed in the etched region contact the substrate to define at least one complete porous structure and porous structures formed elsewhere along the metal layer do not contact the substrate.
17. The method of claim 16 , wherein the metal layer comprises aluminum and the template is an anodic aluminum oxide template.
18. The method of claim 16 , further comprising forming a nanopillar connected to the substrate at the at least one complete porous structure.