Since its isolation by mechanical exfoliation in 2004, graphene has attracted enormous interest from the scientific community not the least because of its unique physical and electronic properties. Among these, graphene’s ballistic electron transport and proximity induced superconductivity make graphene-superconductor (GS) hybrid structures a scientifically promising area

Ekeya, Robin

Zietz, Otto

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PDXScholar (Portland State University)

Portland State UniversityPDXScholarUndergraduate Research & Mentoring Program Maseeh College of Engineering & ComputerScienceSpring 5-23-2018Direct Synthesis of Graphene on Niobium and Niobium NitrideRobin EkeyaPortland State UniversityOtto ZietzPortland State UniversityLet us know how access to this document benefits you.Follow this and additional works at: https://pdxscholar.library.pdx.edu/mcecs_mentoringPart of the Materials Science and Engineering Commons, and the Mechanics of MaterialsCommonsThis Poster is brought to you for free and open access. It has been accepted for inclusion in Undergraduate Research & Mentoring Program by anauthorized administrator of PDXScholar. For more information, please contact pdxscholar@pdx.edu.Citation DetailsEkeya, Robin and Zietz, Otto, "Direct Synthesis of Graphene on Niobium and Niobium Nitride" (2018). Undergraduate Research &Mentoring Program. 27.https://pdxscholar.library.pdx.edu/mcecs_mentoring/27Figure 3. Raman spectra of graphitic films grown on niobium (a) and niobium nitride (b) at 1000° C with a hydrogen-acetylene plasma. Spectrum of graphitic film grown on niobium at 1100° C with acetylene only and no plasma (c).-• We have demonstrated that both niobium and niobium nitride can self-catalyze the dehydrogenation of acetylene gas both with and without a plasma. This is shown by the presence of D, G, and 2D peaks in the Raman spectra, Figure 3.• The progression of the 2D to G peak ratio as we moved from a plasma regime Figure 3 (a & b), to a non plasma regime Figure 3 (c), shows we are moving to more graphene like films in our results. Figure 4 is a reference for the peak ratios we are aiming for.Direct Synthesis of Graphene on Niobium SuperconductorsRobin Ekeya, Otto Zietz, and Dr. Jun JiaoDepartment of Mechanical and Materials Engineering, Portland State UniversityBackground & MotivationResultsDiscussionAcknowledgementsReferencesThe authors acknowledge the support of the Semiconductor Research Corporation (SRC) Education Alliance (award # 2009-UR-2032G) and of the Maseeh College of Engineering and Computer Science (MCECS) through the Undergraduate Research and Mentoring Program (URMP)ObjectiveMethodsWhy direct growth of graphene on niobium?The synthesis few-layer graphene on niobium and niobium nitride nanofilms supported on industry standard silicon dioxide wafersFigure 1. A cartoon of transferred graphene showing impurities trapped in the graphene-superconductor interface (a) , cartoon of directly grown graphene showing a more electron transparent interface (b). An image of graphene’s hexagonal structure (c).Graphene is a single atom thick hexagonal lattice of carbon, see Figure 1 (c). Its isolation and initial characterization in 2004 [1] generated massive interest from the scientific community because of its unique physical and electronic properties. Of interest to this work:• Ballistic electron transport. In graphene electrons have a mean free path in the lattice that is longer than the conductor dimensions, i.e. electrons travel without scattering and with little to no energy dissipation. [2]• Proximity induced superconductivity. Placed in contact with a superconducting material, graphene also turns into a superconductor, i.e. electrons move without resistance, and do not need an external voltage source to maintain a current. [3]Creating highly electron transparent graphene-superconductor interfaces remains difficult, so ballistic conduction in this system is still not well characterized. Direct graphene growth on a superconductor vs transfer promises a higher quality interface, see Figure 1 (a & b). [4]Figure 2. Schematic of PECVD vacuum chamber (a). CAD drawing of PECVD bell jar and acrylic shield (b). Photo of PECVD system with active plasma and resistive heater (c).• Wafers were subjected to various growth regimes in a plasma enhanced chemical vapor deposition (PECVD) system.• Wafers were characterized by Raman spectroscopy to see the effectiveness of the chosen growth regime.• 200 nm niobium and niobium nitride films were deposited on silicon dioxide wafers via chemical vapor deposition (CVD).CVD of niobium on SiO2Direct growth of graphene by PECVDCharacterization by Raman SpectroscopyGrowth trials were performed in a PECVD system designed and built by current research group members, see Figure 2.Growths in custom PECVD system built in houseWhat do these results mean?Figure 4. Raman spectrum of monolayer graphene grown on 1.5 micron copper film in our lab.Conclusions / Future Work• Based on the progression of our results so far, direct growth of graphene on niobium and niobium nitride appears possible.• Next steps are to transfer currently grown films to a bare SiO2 wafer and obtain Raman spectra from this known substrate. This will rule out the possibility of interference of the graphene signal by the niobium substrate.1. K. S. Novoselov, “Electric Field Effect in Atomically Thin Carbon Films,” Science, vol. 306, no. 5696, pp. 666–669, Oct. 2004.2. X. Du, I. Skachko, A. Barker, and E. Y. Andrei, “Approaching ballistic transport in suspended graphene,” Nature Nanotechnology, vol. 3, no. 8, pp. 491–495, Aug. 2008.3. B. M. Kessler, ç. ö. Girit, A. Zettl, and V. Bouchiat, “Tunable Superconducting Phase Transition in Metal-Decorated Graphene Sheets,” Physical Review Letters, vol. 104, no. 4, Jan. 2010.4. C. Tonnoir et al., “Induced Superconductivity in Graphene Grown on Rhenium,” Physical Review Letters, vol. 111, no. 24, Dec. 2013.

Direct Synthesis of Graphene on Niobium and Niobium Nitride

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Direct Synthesis of Graphene on Niobium and Niobium Nitride

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