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1.21.00.80.60.40.20.01

hAl

h2gr

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ArAr

Graphene Processing for Tunable Metasurfaces

Metamaterials enable optical properties that cannot be found in nature. Through the use of graphene intercalation, we seek to create a tunable perfect absorber metamaterial that can be used for low power visible displays. A design for this metasur-face has been developed; however, the graphene processing and characterization for the design have not been fully ex-plored. Here, we study exfoliation techniques and etch rates of graphene for fabrication of the metasurface.

Sarah Ruiz1, Zachary J. Coppens2, and Jason Valentine2

1 Department of Physics, Grinnell College2 Department of Mechanical Engineering, Vanderbilt University

This work was supported by the National Science Foundation under award 1560414. I would also like to thank the VINSE Tech Crew, Anthony Hmelo, Kurt Heinrich, You Zhou, Zhihua Zhu, Austin Howes, andFabian Ugwu.

References:1Laboratory for Graphene, Institute of Physics Belgrade, Serbia. http://www.graphene.ac.rs/exfoliation.html.2Kudriavtsev, Y., Villegas, A., Godines, A., & Asomoza, R. (2005). Calculation of the surface binding ener-gy for ion sputtered particles. Applied Surface Science, 239(3), 273–278. https://doi.org/http://dx.doi.org/10.1016/j.apsusc.2004.06.014

Acknowledgements

Results

Argon Etching of Graphene

• Use graphene exfoliation to transfer layers of graphene onto aluminum samples

• Etch graphene with argon sputtering to increase the speed of diffusion of sodium ions during intercalation

• Measure the step heights of the graphene flakes using AFM to determine etch rates

AluminumBefore Etch

Aluminum

After Etch

h1gr

Abstract

Conclusion

Fabrication Procedure

Schematic of unit cell with intercalation of sodium ions.

Simulated reflection curves for metama-terial unit cell. As in-tercalation occurs, the spacer height in-creases making the color change.

AFM images of graphene flake on aluminum (left) and alumi-num with PMMA mask for etch (right).

Simulated transmission for 6 graphene sheets at decreasing fermi levels.

Decreasing Fermi Level

Schematic of 6 graphene sheet unit cell used for simula-tion.

Chemical Potential (eV)

Aluminum

Metamaterial Modeling

Refle

ctio

n

Wavelength (nm)Etching Parameters: RF Power = 19W, ICP Power = 300W, Flow rate = 100 s.c.c.m., Table temperature = 10K, Pressure = 50mTorr

Graphene Exfoliation

6 nm graphene appear etched in 1 minute

1Laboratory for Graphene, Institute of Physics Bel-grade, Serbia

By sputter etching samples of aluminum and graphene we find that they both etch at 0.8nm/minute. This meets our expecta-tions because sputter etching is a nonreactive method that will etch the sample if the surface binding energies are less than the kinetic energy of an incoming argon ion 2. This research will be used in the fabrication of both metallic and non-metal-lic metasurfaces for low power displays.

1. Clean sample.2. Remove graphene layers from graphite with adhesive tape.3. Use tape to transfer graphene onto sample.4. Anneal at 100o C for 2 minutes.5. Slowly remove adhesive tape leaving behind graphene.

Metallic Metamaterial

Non-metallic Metamaterial

Before Etch

After Etch

1 Minute

Height Sensor Height Sensor0.0μm 15μm15μm 0.0μm

26.4nm

-17.4nm-21.3nm

23.0nm

Etch Rate Difference [nm/minute]-6 -4 -2 0 2

Occ

urre

nces

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12Etch Rate Difference = Al-Gr

• Graphene and Aluminum etch at about the same rate• Etch Rate of Al = 0.8nm/min, however this is only based on

one sample and should be verified