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

 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.Exfoliate HOPG 2.Raman Spectroscopy 3.AFM 4.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

 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 (B-C peak), 1352 cm -1 (D peak), 1368 cm -1 (h-BN peak)

 No clear trend found between O 2 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 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  [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  [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), (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