Enhancement structures for surface-enhanced Raman scattering

1. An enhancement structure for use in surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence-based analysis, the structure comprising: a substrate comprising a top surface; an array of nanoscale metal-insulator-metal (MIM) structures arranged on the top surface of the substrate; an array of dielectric adhesion layers deposited between the top surface of the substrate and the array of nanoscale MIM structures; and one or more additional dielectric layers, having a tilted orientation, deposited around at least a periphery of one or more MIM structures.

2. The enhancement structure of claim 1 , wherein the array of nanoscale metallic structures comprises at least one of gold (Au), silver (Ag), aluminum (Al), and one or more alloys thereof.

3. The enhancement structure of claim 1 , wherein the array of dielectric layers comprises at least one of silicon dioxide (SiO 2 ), magnesium oxide (MgO), silicon nitride (Si 3 N 4 ), and aluminum oxide (Al 2 O 3 ).

4. The enhancement structure of claim 1 , wherein each of the array of dielectric layers has a thickness of less than 10 nm.

5. The enhancement structure of claim 1 , wherein each nanoscale MIM structure comprises a bottom surface adhered to the top surface of the substrate via a respective dielectric layer.

6. The enhancement structure of claim 5 , wherein at least some dielectric layers have a surface area that is greater than a surface area of a bottom surface of a respective nanoscale MIM structure such that a portion of a dielectric layer extends beyond a perimeter of a bottom surface of a respective nanoscale MIM structure.

7. The enhancement structure of claim 1 , wherein a refractive index of the substrate at Raman pump and Raman Stokes wavelengths is at least 1.5.

8. The enhancement structure of claim 1 , wherein the substrate comprises glass.

9. The enhancement structure of claim 1 , wherein the substrate comprises silicon dioxide (SiO 2 ).

10. The enhancement structure of claim 1 , wherein the substrate comprises an amorphous sapphire material.

11. The enhancement structure of claim 1 , further comprising a dielectric film layer deposited on the top surface of the substrate, wherein the dielectric film layer comprises a refractive index at Raman pump and Raman Stokes wavelengths greater than 1.5.

12. The enhancement structure of claim 11 , wherein the dielectric film layer comprises silicon nitride (Si 3 N 4 ) or silicon oxynitride (Si x N y O).

13. The enhancement structure of claim 11 , wherein the dielectric film layer is deposited between the top surface of the substrate and the array of nanoscale MIM structures.

14. The enhancement structure of claim 1 , wherein at least some of the array of nanoscale MIM structures have a circular shape.

15. The enhancement structure of claim 1 , wherein at least some of the array of nanoscale MIM structures have an elliptical shape with a ratio other than 1:1.

16. The enhancement structure of claim 1 , wherein the array of nanoscale MIM structures comprises an array of individual discs.

17. The enhancement structure of claim 1 , wherein the array of nanoscale MIM structures comprises an array of pairs of discs.

18. The enhancement structure of claim 17 , wherein each pair of discs comprises an outer annular disc and an inner annular disc coaxially aligned with one another.

19. The enhancement structure of claim 1 , wherein an electric dipole resonance of the array of nanoscale MIM structures is tuned to match a Raman pump wavelength.

20. The enhancement structure of claim 1 , wherein a magnetic dipole resonance of the array of nanoscale MIM structures is tuned to match a Raman Stokes wavelength.

21. The enhancement structure of claim 1 , wherein the insulating layer of the MIM structure comprises at least one of silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), and aluminum oxide (Al 2 O 3 ).

22. The enhancement structure of claim 1 , wherein the metal of the MIM structure comprises at least one of one of gold (Au), silver (Ag), aluminum (Al), and one or more alloys thereof.

23. The enhancement structure of claim 1 , wherein at least some dielectric adhesion layers have a surface area that is greater than a surface area of a bottom surface of a respective one of the MIM structures such that a portion of a dielectric adhesion layer extends beyond a perimeter of a bottom surface of a respective MIM structure and is exposed on the top surface of the substrate.

24. The enhancement structure of claim 1 , wherein the additional dielectric layer has a varying thickness.

25. The enhancement structure of claim 24 , wherein the additional dielectric layer has a first thickness that is greater than a thickness of an underlying dielectric adhesion layer and a second thickness that is less than a thickness of the underlying dielectric adhesion layer.

26. The enhancement structure of claim 1 , wherein the additional dielectric layer has a thickness of less than 10 nm.

27. The enhancement structure of claim 25 , wherein the additional dielectric layer has a profile that tapers from the first thickness to the second thickness.

28. The enhancement structure of claim 27 , wherein the additional dielectric layer is deposited at an angle relative to the top surface of the substrate.

29. The enhancement structure of claim 1 , wherein the dielectric adhesion layers comprise at least one of silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), and aluminum oxide (Al 2 O 3 ).

30. The enhancement structure of claim 1 , wherein the one or more additional dielectric layers comprise at least one of silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), and aluminum oxide (Al 2 O 3 ).

31. The enhancement structure of claim 1 , wherein the dielectric adhesion layers each comprise a metal oxide.

32. The enhancement structure of claim 31 , wherein the metal oxide inhibits loss at Raman pump and Raman Stokes wavelengths.