ZnO /metal layered 3D Photonic crystals

1. ZnO/metal layered 3D Photonic crystals Michael McMaster, Dr. Tom Oder, Dr. Donald Priour Dept. of Physics and Astronomy, Youngstown State University, Youngstown, OH

2. What to Expect • What is a Photonic Crystal? • Experimental Procedure • Modeling/Results • Conclusion

3. Photonic Crystal • “Photonic crystals are materials patterned with a periodicity in dielectric constant, which can create a range of ‘forbidden’ frequencies called a photonic bandgap. Photons with energies lying in the bandgap cannot propagate through the medium. This provides the opportunity to shape and mould the flow of light for photonic information technology.” • J.D. Joannopoulos, Pierre R. Villeneuve & Shanhui Fan • Applications include • Waveguides • LED light extraction • Ultrafast photonic crystal nanocavity laser • High speed communication • High speed information processing

4. CallophrysGryneus Vinodkumar et. Al. (2010)

5. Peacock Paridessesostris Weevil and two Longhorns Vinodkumar et. Al. (2010) CERN Courier (2005) Vigneron et. Al. (2012)

6. Joannopoulos et. Al. (2008)

7. Pillars Comprise a 3-D Photonic Crystal

8. ZnO/Cr and ZnO/Al Multilayer Films • Substrate: double-side polished sapphire • Base Pressure: 10-7 mtorr • Preheat temperature:~700°C • Depositions temperature: 300°C • Deposition pressure: 10 mtorr • Ambient gas: Ar • Flow Rate: 10 sccm • Presputter: 3 min • ZnO Buffer Layer: 250 nm • Layer thicknesses: • ZnO/Cr (120 nm/12 nm)x10 • ZnO/Cr (90 nm/ 5nm) x10 • ZnO/Al (170 nm/ 5nm) x8

9. How can we make 3-D Photonic Crystals? Bottom Up Top Down FIB Holes in 1-D crystals Accurate, small feature size • Shadow mask sputtering • Periodic Array of Pillars • Quick and easy

10. Some Quick Physics Facts • Index of Refraction: • Snell’s law • The Electric Field Equation:

11. Mathematical Interlude n1 n2 n3 … nN-1nN ns A0 A1 A2 … … AN As B0 B1 B2 … … BNBs x0 x1 x2 … … xNxs The Electric Field can be shown for different refractive indices as: So we get a vector representing the amplitudes of the wave function. Yeh. (2004)

12. Mathematical Interlude (continued) We can describe light at the interface of materials with different refractive indices with the dynamical matrices: so that light passing through the interface responds such that . Also, as it travels through a material, the change is shown by the transfer matrix: Yeh. (2004)

13. Mathematical Interlude (Recap) • By acting on the vector representing light passing through the system with the matrices describing the environment we can predict the transmission spectrum. • Recall: But metals have an imaginary index of refraction (n) so let’s write: But Φhas real an imaginary parts Re(Φ) and Im(Φ) so where we see the Decay term. Yeh. (2004)

14. 1-D Photonic Crystals • Refractive Indices in Visible Spectrum • ZnO 2.0 • Cr 3.2 • Al 1.3 • Layer thicknesses of samples: • ZnO/Cr (120 nm/12 nm)x10 • ZnO/Cr (90 nm/ 5nm) x10 • ZnO/Al (170 nm/ 5nm) x8

15. Transmission Spectrum Actual Transmission Spectrum Theoretical Transmission Spectrum ?

16. After Annealing ZnO/Cr 1-D photonic Crystal Theoretical Model

17. After Annealing ZnO/Cr 1-D photonic Crystal Theoretical Model

18. Remember those cosines? ZnO/Cr (120nm/12nm)x10 Theoretical Model Photonic Crystal Not a Photonic Crystal

19. We can Control the Band-Gap! (this Time in Blue) Band-Gap ZnO/Cr 1-D photonic Crystal Theoretical Model

20. Aluminum • Band-gap is maximized when n1d1=n2d2 • nZnO=2.0 nAl=1.3 • ZnO/Al (170 nm/ 5nm) x8 • We predict a smaller band-gap ZnO/Al 1-D photonic Crystal Theoretical Joannopoulos et. Al. (2008)

21. EDX Results (Not Chromium Oxide) ZnO/Cr (120 nm/12 nm)x10 Expected Transmission Spectrum if Chromium had oxidized. (CrO3 refractive index 2.55) ZnO/Cr (90 nm/ 5nm) x10 ZnO/Al (170 nm/ 5nm) x8

22. Annealing in Different Gas

23. 4-Point Probe Results Bulk Resistivity (Ω∙cm) Pre Annealing Post Annealing ZnO/Cr (120 nm/12 nm)x10 .012 15 ZnO/Cr (90 nm/ 5nm) x10 .0027 310 ZnO/Al (170 nm/ 5nm) x8 too resistive .095

24. What Next??? • Produce 3-D photonic crystals • using Shadow mask or FIB • Model in higher dimension • TEM/AFM for layer thickness What we Expect What we Hope For • Evidence of 3-D from diffraction pattern • Measureable band-gaps in oblique directions • Improved modeling • both polar and radial angle band-gap dependance • Predict band-gap • Test the effect of electric field on optical the band-gap

25. References • VinodkumarSaranathan, Chinedum O. Osuji, Simon G. J. Mochrie, HeesoNoh, Suresh Narayanan, Alec Sandy, Eric R. Dufresne, and Richard O. Prum. Structure, function, and self-assembly of single network gyroid (I4132) photonic crystals in butterfly wing scales PNAS 107 (26) 11676-11681 (2010). • Joannopoulos, John D., Steven G. Johnson, Joshua N. Winn, Robert D. Meade. Photonic Crystals Modeling the Flow of Light Second Edition. Princeton University Press (2008). • Yeh,Pochi. Optical Waves In Layered Media: 2nd (second) Edition. Whiley Press (2004). • Peacock feathers prove photonic crystals cast brown light in nature. CERN Courier. Aug 22, 2005 • JoannopoulosJ.D. , Pierre R. Villeneuve and ShanhuiFan. Photonic Crystals: putting a new twist on light. Nature 386 (13) 143-149 (1997) • Vigneron, Jean Pol, and Priscilla Simonis. Natural photonic crystals.Physica B Condensed Matter 407 (20) 4032-4036 (2012)

26. Acknowledgements • We gratefully acknowledge support of funds from NSF (DMR#1006083) and from the State of Ohio (Third Frontier - RC-SAM). • Support and funds from Youngstown State University • I would also like to thank Dr. Jim Andrews, Jessica Shipman and Matt Kelly and Dr. George Yates for helping with this project.

27. Any Questions? Xkcd.com