Raman Spectroscopy of 2D Materials

Report
Kevin Cai, AMSA Charter School
Matthew Greenlaw, Pioneer Charter School of Science
Dr. Birol Ozturk, Northeastern University
Professor Swastik Kar, Physics, Northeastern University
Laboratory for Graphene Research
31 July 2014

Graphene
◦ 2D sheet of carbon
◦ Conductor
◦ Stronger than steel
Mechanical exfoliation, CVD
 Applications

◦ Films, composite materials
◦ Biological engineering
◦ Storage
Image from http://en.wikipedia.org/wiki/Graphene
Laser at set
wavelength aimed
at sample
 Reflected beam has
a different
wavelength due to
vibrations
 Raman shift
(wavenumber, cm-1)


Three peaks
◦ D peak (~1350 cm-1) – defect
◦ G peak (~1600 cm-1) – in-plane vibrations
◦ G’ peak (~2700 cm-1) – out-of-plane vibrations

Creates
topographical image
◦ Scanning probe (with
laser aimed at the tip)
vibrates at a set
frequency/amplitude
◦ Changes in amplitude
are recorded
~4 nm
1.
How does the thickness of a graphene
sample correlate to its Raman spectrum?
2.
How does O2 flow rate affect the doping of
graphene with boron nitride?

Procedure:
1.
2.
3.
4.
Exfoliate HOPG
Raman Spectroscopy
AFM
Graph IG’/IG ratio vs. thickness
IG’/IG ratio generally decreases as thickness
increases
 Along with lower intensity, G’ peak becomes
wider with increasing thickness (multilayer)

Graphene – conductor, zero band gap
 Boron nitride – semiconductor

◦ Boron nitride domains are isostructural to
graphene

 2D semiconductor alloy with controlled
band gap
Image from: Servincli, H., et.al. “Effects of domains in phonon conduction through
hybrid boron nitride and graphene sheets.” American Physical Society. 2011.

Procedure
◦ Samples grown by CVD; B, N, C, and O present
 O2 flow rates (sccm): 0, 2, 4, …, 10
◦ Raman Spectroscopy
◦ Broad peak at ~1355 cm-1 decomposed
 1330 cm-1 (B-C peak), 1352 cm-1 (D peak), 1368
cm-1 (h-BN peak)

No clear trend found between O2 flow rate
and h-BN domain coverage
◦ More data needed

Mechanically Exfoliated Graphene
◦ Improve exfoliation strategy, scan/measure more
samples

BN-doped Graphene
◦ Use curve fitting on more Raman spectra of
domains
◦ Limit domain loss at higher O2 flow rate

[1] Servincli, H., et.al. “Effects of domains in phonon conduction
through hybrid boron nitride and graphene sheets.” American
Physical Society. 2011.
<http://journals.aps.org/prb/abstract/10.1103/PhysRevB.84.205444>.

[2] Wang, Lifeng, et.al. “Monolayer Hexagonal Boron Nitride Films with Large
Domain Size and Clean Interface for Enhancing the Mobility of GrapheneBased Field-Effect Transistors.”Wiley Online Library. 2014.
<http://onlinelibrary.wiley.com/doi/10.1002/adma.201304937/full>.

[3] Zhou, H., Yu, F., Yang, H., Qiu, C., Chen, M., Hu, L., ... & Sun, L.. “Layerdependent morphologies and charge transfer of Pd on n-layer graphenes”.
Chem. Commun., 47(33), 9408-9410. (2011).
Dan Rubin and Dr. Birol Ozturk – Research
mentors
 Center for STEM Education
 Young Scholars Program and Team

◦ Claire Duggan – Director
◦ Kassi Stein, Jake Holstein, Chi Tse – Coordinators

Professor Swastik Kar

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