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 O 2 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  O 2 flow rates (sccm): 0, 2, 4, …, 10 Raman Spectroscopy Broad peak at ~1355 cm -1 decomposed  1330 cm -1

cm -1

(B-C peak), 1352 cm

(h-BN peak)

-1 (D peak), 1368

 No clear trend found between O 2 ◦ and h-BN domain coverage More data needed flow rate

 ◦ 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 O 2 flow rate

 [1] Servincli, H., et.al. “Effects of domains in phonon conduction through hybrid boron nitride and graphene sheets.” American Physical Society. 2011.

.

 [2] Wang, Lifeng, et.al. “Monolayer Hexagonal Boron Nitride Films with Large Domain Size and Clean Interface for Enhancing the Mobility of Graphene Based Field-Effect Transistors.”Wiley Online Library. 2014. .

 [3] Zhou, H., Yu, F., Yang, H., Qiu, C., Chen, M., Hu, L., ... & Sun, L.. “Layer dependent 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