Negative refractive index materials and methods for making same
Embodiments of the invention described herein include metamaterials that exhibit negative permittivity and negative permeability at optical frequencies, methods for preparing such materials, and devices prepared from same.
1. A method for producing a metamaterial comprising:
combining a matrix material having a negative permittivity (ε) at optical frequencies and nanoparticles having a high dielectric constant structured to cause negative permeability (μ) at optical frequencies due to a scattering resonance to create a powder mixture; and
sintering at reduced temperature to form a consolidated metamaterial film.
2. The method of claim 1 , further comprising the steps of:
dispersing the powder mixture in a solvent; and
allowing a film of the powder mixture to form on a substrate before sintering at reduced temperature.
3. The method of claim 2 , wherein the solvent is selected from ethanol, methanol, acetone, and any combination of ethanol, methanol, and acetone.
4. The method of claim 2 , wherein the substrate is a silicon wafer.
5. The method of claim 1 , wherein the consolidated metamaterial film is from about 100 nm to about 100 μm thick.
6. The method of claim 1 , wherein the sintering is conducted using an e-beam.
7. The method of claim 1 , wherein the sintering comprises a dosage e-beam energy at an interval of from about 25,000 kGy to about 150,000 kGy.
8. The method of claim 1 , wherein the reduced temperature is less than about 150° C.
9. The method of claim 1 , wherein the sintering occurs under nitrogen.
10. The method of claim 1 , further comprising milling a matrix material and nanoparticles to produce a milled powder.
11. The method of claim 1 , wherein the matrix material is polycrystalline magnesium diboride (MgB 2 ).
12. The method of claim 1 , wherein the matrix material comprises nanoparticles of material selected from gold (Au), platinum (Pt), copper (Cu), silver (Ag), nickel (Ni), palladium (Pd), cadmium (Cd), zinc (Zn), and combinations thereof.
13. The method of claim 1 , wherein the nanoparticles are selected from titanium oxide (TiO 2 ), zirconium oxide (ZrO 2 ), and combinations thereof.
14. The method of claim 1 , wherein the nanoparticles are silicon carbide (SiC) nanoparticles.
15. The method of claim 1 , wherein the nanoparticles comprise from about 10% by volume to about 50% by volume of the metamaterial.
16. A method for producing a metamaterial comprising:
dispersing a magnesium salt in organic solvent and reacting with a borohydride compound to form a solution;
adding water to the solution to form a second solution;
precipitating magnesium diboride from the second solution;
collecting the precipitate; and
reacting under an atmosphere of diborane.
17. The method of claim 16 , wherein the magnesium salt is magnesium chloride or magnesium boride.
18. The method of claim 16 , wherein the borohydride is sodium borohydride.
19. The method of claim 16 , further comprising spin casting the precipitate.
20. The method of claim 16 , further comprising reacting the precipitate under an atmosphere of diborane.
21. A method for producing a metamaterial comprising:
combining a matrix material having a negative permittivity (ε) at optical frequencies and nanoparticles having a high dielectric constant structured to cause negative permeability (μ) at optical frequencies due to a scattering resonance to create a powder mixture;
encapsulating the powder mixture in a container; and
consolidating the powder mixture by hot isostatic pressing to form a metamaterial billet.
22. The method of claim 21 , further comprising cutting metamaterial billet.
23. The method of claim 21 , wherein the hot isostatic pressing is carried out at from about 600° C. to about 700° C.
24. The method of claim 21 , wherein the matrix material is polycrystalline magnesium diboride (MgB 2 ).
25. The method of claim 21 , wherein the matrix material comprises nanoparticles of material selected from gold (Au), platinum (Pt), copper (Cu), silver (Ag), nickel (Ni), palladium (Pd), cadmium (Cd), zinc (Zn), and combinations thereof.
26. The method of claim 21 , wherein the nanoparticles are selected from, titanium oxide (TiO 2 ), zirconium oxide (ZrO 2 ), and combinations thereof.
27. The method of claim 21 , wherein the nanoparticles are silicon carbide (SiC) nanoparticles.
28. The method of claim 21 , wherein the nanoparticles comprise from about 10% by volume to about 50% by volume of the metamaterial.