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ZnO /metal layered 3D Photonic crystals. Michael McMaster , Dr. Tom Oder, Dr. Donald Priour. Dept. of Physics and Astronomy, Youngstown State University, Youngstown, OH. What to Expect. What is a Photonic Crystal? Experimental Procedure Modeling/Results Conclusion. Photonic Crystal.

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ZnO/metal layered 3D Photonic crystals

Michael McMaster, Dr. Tom Oder, Dr. Donald Priour

Dept. of Physics and Astronomy,

Youngstown State University, Youngstown, OH


What to Expect

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

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


Vinodkumar et. Al. (2010)




Weevil and two Longhorns

Vinodkumar et. Al. (2010)

CERN Courier (2005)

Vigneron et. Al. (2012)


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

How can we make 3-D Photonic Crystals?

Bottom Up

Top Down


Holes in 1-D crystals

Accurate, small feature size

  • Shadow mask sputtering
  • Periodic Array of Pillars
  • Quick and easy

Some Quick Physics Facts

  • Index of Refraction:
  • Snell’s law
  • The Electric Field Equation:

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)


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)


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)


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

Transmission Spectrum

Actual Transmission Spectrum

Theoretical Transmission Spectrum



After Annealing

ZnO/Cr 1-D photonic Crystal

Theoretical Model


After Annealing

ZnO/Cr 1-D photonic Crystal

Theoretical Model


Remember those cosines?

ZnO/Cr (120nm/12nm)x10

Theoretical Model

Photonic Crystal

Not a Photonic Crystal


We can Control the Band-Gap!

(this Time in Blue)


ZnO/Cr 1-D photonic Crystal

Theoretical Model



  • 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


Joannopoulos et. Al. (2008)


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


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


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


  • 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)


  • 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.