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

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

“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 Photonic Crystal –Waveguides –LED light extraction –Ultrafast photonic crystal nanocavity laser –High speed communication –High speed information processing

Callophrys Gryneus Vinodkumar et. Al. (2010)

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

Joannopoulos et. Al. (2008)

Pillars Comprise a 3-D Photonic Crystal

ZnO/Cr and ZnO/Al Multilayer Films Substrate: double-side polished sapphire Base Pressure: 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

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

Some Quick Physics Facts

n 1 n 2 n 3 … n N-1 n N n s A 0 A 1 A 2 … … A N A s B 0 B 1 B 2 … … B N B s x 0 x 1 x 2 … … x N x s The Electric Field can be shown for different refractive indices as: So we get a vector representing the amplitudes of the wave function. Mathematical Interlude Yeh. (2004)

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: Mathematical Interlude (continued) Yeh. (2004)

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 Φ has real an imaginary parts Re( Φ ) and Im( Φ ) so where we see the Decay term. Mathematical Interlude (Recap) Yeh. (2004)

Refractive Indices in Visible Spectrum –ZnO2.0 –Cr3.2 –Al1.3 Layer thicknesses of samples: –ZnO/Cr (120 nm/12 nm)x10 –ZnO/Cr (90 nm/ 5nm) x10 –ZnO/Al (170 nm/ 5nm) x8 1-D Photonic Crystals

Transmission Spectrum Theoretical Transmission Spectrum Actual Transmission Spectrum

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

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

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

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

Band-gap is maximized when n 1 d 1 =n 2 d 2 n ZnO =2.0n Al =1.3 ZnO/Al (170 nm/ 5nm) x8 We predict a smaller band-gap Aluminum Joannopoulos et. Al. (2008) ZnO/Al 1-D photonic Crystal Theoretical

ZnO/Cr (120 nm/12 nm)x10 ZnO/Cr (90 nm/ 5nm) x10 ZnO/Al (170 nm/ 5nm) x8 EDX Results (Not Chromium Oxide) Expected Transmission Spectrum if Chromium had oxidized. (CrO 3 refractive index 2.55)

Annealing in Different Gas

4-Point Probe Results ZnO/Cr (120 nm/12 nm)x ZnO/Cr (90 nm/ 5nm) x ZnO/Al (170 nm/ 5nm) x8too resistive.095 Pre AnnealingPost Annealing Bulk Resistivity (Ω∙cm)

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

Vinodkumar Saranathan, Chinedum O. Osuji, Simon G. J. Mochrie, Heeso Noh, 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) (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 Joannopoulos J.D., Pierre R. Villeneuve and Shanhui Fan. Photonic Crystals: putting a new twist on light. Nature 386 (13) (1997) Vigneron, Jean Pol, and Priscilla Simonis. Natural photonic crystals. Physica B Condensed Matter 407 (20) (2012) References

We gratefully acknowledge support of funds from NSF (DMR# ) 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. Acknowledgements

Any Questions? Xkcd.com