Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F30: 2D Materials: Properties and CharacterizationFocus
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Sponsoring Units: DMP Chair: Jiwoong Park, University of Chicago Room: 293 |
Tuesday, March 14, 2017 11:15AM - 11:27AM |
F30.00001: Nonlinear light mixing by graphene plasmons B. Van Duppen, D. Kundys, I. Torre, O. P. Marsall, F. Rodriguez, M. Polini, A. N. Grigorenko Graphene is known to be a strongly optical nonlinear material. Its nonlinear response can also be enhanced by graphene plasmons. We report a new nonlinear electro-absorption effect observed in nanostructured graphene due to excitation of localized graphene plasmons. We experimentally detect and theoretically explain enhanced nonlinear mixing of near-infrared and mid-infrared light in arrays of graphene nanoribbons. Strong compression of light by graphene plasmons implies that the effect is non-local in nature and orders of magnitude larger than the conventional local graphene nonlinearity. [Preview Abstract] |
Tuesday, March 14, 2017 11:27AM - 11:39AM |
F30.00002: Topological photonics in the graphene family Diego Dalvit, Wilton Kort-Kamp, Pablo Rodriguez-Lopez, Alejandro Manjavacas, Lilia Woods In the last few years, notions of topology have been applied to both electronic and photonic systems, uncovering a myriad of novel effects. The recent expansion of the graphene family by adding silicene, germanene, and stanene opens a promising platform to probe the complex interplay between topology, photonics, and quantum materials in 2D staggered Dirac systems. A central quantity in the description of light-matter interactions at the nanoscale is the photonic local density of states (ph-LDOS) that drives basic processes such as spontaneous emission, thermal emission and absorption. In this talk we show that the ph-LDOS can undergo various phase transitions and present topological behavior, all enabled by the rich electronic phase diagram of the graphene family. [Preview Abstract] |
Tuesday, March 14, 2017 11:39AM - 11:51AM |
F30.00003: Defect-induced Non-linear Optical Properties in BN Yongchang Dong, Prakash Parajuli, Longyu Hu, Ramakrishna Podila, Apparao Rao Emerging two-dimensional materials are known for their excellent optical properties. Unlike most 2D materials which display saturable absorption, boron nitride (BN) is an exception in that it exhibits multi-photon absorption. Although a two-photon absorption process was proposed to explain intrinsic non-linear absorption in BN, we find higher order nonlinearities such as five-photon absorption at 1064 nm. Interestingly, as will be discussed in this talk, our density functional theory calculations, finite-element analysis simulation, and experimental studies present compelling evidence that defect-induced mid-gap states in BN reduce higher order nonlinearities to enable two-photon absorption. Lastly, ~strong nonlinear light-matter interactions in BN are found to induce defects, which convert five-photon absorption to two-photon \textit{in situ}. [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:03PM |
F30.00004: Near-field study in hBN moir\'{e} superlattices. Guangxin Ni, Haomin Wang, Jhihsheng Wu, Lingxiu Chen, Alexander Swinton McLeod, Xiaoming Xie, Michael Fogler, Dimitri Basov Interlayer coupling in atomic van der Waal (vdW) heterostructures plays a rather unique role in controlling their optical and electronic properties. The character of the interlayer coupling can be manipulated by a particular stacking arrangement of the proximal layers and by adjusting the orientation of the neighboring planes. The latter method is known to trigger the long-range periodic modulations referred to as moir\'{e} superlattices. Implications of moir\'{e} patterns for the properties of twisted graphene bilayers and in graphene on hexagonal boron nitride (hBN) are being systematically explored. Moir\'{e} patterns in other vdW systems are yet to be revealed. Here we report the observation of moir\'{e} superlattices with a giant periodicity (\textasciitilde 500 nm) in exfoliated hBN crystals subjected to thermal treatment. A combination of atomic force topographic imaging and scanning nano-infrared spectroscopy has implicated both strain and layer rotations in the observed effects. [Preview Abstract] |
Tuesday, March 14, 2017 12:03PM - 12:15PM |
F30.00005: Direct deposition of 2D boron nitride on epitaxial graphene surfaces James Gigliotti, Xin Li, Suresh Sundaram, Jean-Philippe Turmaud, Dogukan Deniz, Yiran Hu, Yue Hu, Vladimir Prudkovskyi, Claire Berger, Abdallah Ougazzaden, Walt deHeer Despite much interest in epitaxial graphene for nanoelectronics, integrated dielectrics remain challenging. Boron nitride (BN) is a 2D layered dielectric isomorph of graphene which greatly reduces substrate and gate induced scattering in graphene devices. While epitaxial graphene does not suffer from substrate effects, graphene, in general, is sensitive to environmental contamination and requires integrated gates to explore transport phenomenon and develop nanoelectronic devices. However, direct deposition of BN, as well as other 2D semiconductors, onto epitaxial graphene is difficult as growth tends to fall into the Stranski-Krastanov regime. Here, we present evidence of 2D BN layers deposited directly onto epitaxial graphene surfaces via a metalorganic vapor phase epitaxy (MOVPE) process utilizing triethylborane (TEB) and ammonia as the boron and nitrogen sources, respectively. The BN layer exhibits a pleated morphology, indicative of biaxial strain in a 2D van der Waals solid. HR-XRD indicates a highly ordered film and pure sp2 bonding throughout the BN layer was confirmed via XPS. The underlying graphene was probed with Raman spectroscopy and LEED which show no structural change compared to before BN deposition. [Preview Abstract] |
Tuesday, March 14, 2017 12:15PM - 12:27PM |
F30.00006: Optical spectroscopy and photo modification of individual single-photon emitters in hexagonal boron nitride Harishankar Jayakumar, Zav Shotan, Christopher Considine, Mažena Mazkoit, Helmut Fedder, joerg Wrachtrup, Audrius Alkauskas, Marcus Doherty, Vinod Menon, Carlos Meriles Fluorescent defects recently observed under ambient conditions in hexagonal boron nitride (h-BN) promise to open novel opportunities for the implementation of on-chip photonic devices that rely on identical photons from single emitters. Here we report on the room temperature photo-luminescence dynamics of individual emitters in multilayer h-BN flakes exposed to blue laser light. Comparison of optical spectra recorded at successive times reveals considerable spectral diffusion, possibly the result of slowly fluctuating, trapped-carrier-induced stark shifts. Large spectral jumps --- reaching up to 100 nm --- followed by bleaching are observed in most cases upon prolonged exposure to blue light, an indication of one-directional, photo-chemical changes likely taking place on the flake surface. Remarkably, only a fraction of the observed emitters also fluoresces on green illumination suggesting a more complex optical excitation dynamics than previously anticipated and raising questions on the physical nature of the atomic defect at play. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 12:39PM |
F30.00007: A Novel Method for Analyzing Low Doping in Graphene Xuanye Wang, Anna Swan Raman spectroscopy provides a non-destructive method for analyzing graphene’s properties. For example, graphene’s Raman response of the G peak and 2D peak to strain and charge has been effectively used for optically characterizing the strain and charge state [1]. The Raman peaks shift nearly linearly with strain and doping following different correlations for strain and positive and negative charge. However, this rule is no longer valid in the low doping regime within the Kohn anomaly. Here we present a method for probing graphene’s doping level down to sub-Kohn anomaly scale using the Raman peak charge evolution on suspended graphene and graphene encapsulated in hexagonal boron nitride. By analyzing samples with low accidental doping, we obtain statistical behavior of how the Raman peaks evolve in this regime as a function of doping caused by charge puddles. This method allows doping analysis to orders of magnitude lower charge density than traditional $\omega_{2D}$ v.s. $\omega_G$ Raman shift study. This highly sensitive method could be used to correlate with graphene’s electrical transport properties. [1]Lee, J. E.; Ahn, G.; Shim, J.; Lee, Y. S.; Ryu, S. Nat. Commun. 2012, 3, 1024 [Preview Abstract] |
Tuesday, March 14, 2017 12:39PM - 12:51PM |
F30.00008: Comparison of VVV Auger electron spectra from single and multilayer graphene and graphite. V A Chirayath, V Callewaert, A J Fairchild, M D Chrysler, R W Gladen, S K Imam, A R Koymen, R Saniz, B Barbiellini, K Rajeshwar, B Partoens, A H Weiss A direct observation of a low energy electron peak in the positron annihilation induced Auger electron spectra (PAES) from a single layer of graphene was made recently. A low energy positron beam (\textless 1.25 eV) was used to deposit the positron on single layer graphene on a Cu substrate and the low energy peak was designated as VVV following the X-ray notation. The PAES signal is almost entirely from the top graphene layer due to the trapping of positrons in the image potential well on the surface of graphene. We utilize this monolayer sensitivity of PAES to compare the shape of the VVV Auger peak from the single layer graphene to the shapes of the VVV Auger peak obtained from multilayer graphene on Cu and from highly oriented pyrolytic graphite (HOPG). The VVV Auger peak from multilayer graphene on Cu and HOPG shows a systematic shift towards lower energies relative to the VVV Auger peak from the single layer graphene. The influence of the hole-hole interaction in distorting and shifting the VVV Auger spectra are discussed in relation to this observed shift. [Preview Abstract] |
Tuesday, March 14, 2017 12:51PM - 1:03PM |
F30.00009: Effect of vacancy in penta-graphene nanoribbons: Afirst principals study Khaldoun Tarawneh, Nabil Al-Aqtash, Renat Sabirianov Penta-graphene has been proposed recently as a new stable carbon alltrope which is stronger than graphene. To farther explore its properties, we use the first-principals calculations to reveal that the electronic properties of penta-graphene nanoribbons can be modified in the presence of vacancy defect. Our calculations showed that the band gap of penta-graphene nanoribbons changes with changing the width of the ribbons and on the position of the vacancy relative to its edge. The vacancy formation energy is calculated to be 8.42 eV in the middle of the ribbons and decreases to 6.8 eV when the vacancy position is close to the edge of the ribbon. These results for a stable nanoribbon with a large band gap is promising for designing optoelectronic devices. [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:39PM |
F30.00010: 2D Materials: Synthesis, Defects, Structure and Properties Invited Speaker: Peter Beton |
Tuesday, March 14, 2017 1:39PM - 1:51PM |
F30.00011: Epitaxial Graphene Induced Surface Reconstruction in Ge(110) Revealed by High-Resolution X-ray Diffraction and Scanning Tunneling Microscopy Gavin Campbell, Brian Kiraly, Andrew Mannix, Mark Hersam, Michael Bedzyk, Nathan Guisinger, Robert Jacobberger, Michael Arnold Understanding and engineering the properties of single-crystal surfaces has been critical in developing functional microelectronics at the nanoscale. Previously achieved through covalently bonded adatoms at surfaces, here we report how weakly bonded van der Waals' solids influence the development of new surface reconstructions in the EG/Ge(110) system. Employing scanning tunneling microscopy (STM), in-plane X-ray diffraction (XRD), and crystal truncation rod scattering (CTR) we investigate EG/Ge(110) and present a Ge(110) reconstruction stabilized by the presence of epitaxial graphene unseen in bulk semiconductor surfaces. The combined STM and XRD results show the EG/Ge(110) interface, upon annealing, rearranges into a (6x2) superstructure persistence over large areas of the EG/Ge(110). CTR studies confirm the vdW gap and reveal that graphene sits atop the surface reconstruction with a 0.34 nm spacing. This structure represents a new avenue towards nanoscale engineering, using a vdW atomic layer to induce new stable surface reconstructions. [Preview Abstract] |
Tuesday, March 14, 2017 1:51PM - 2:03PM |
F30.00012: Single-Layer graphene growth on crystalline Ni(111) and Ni(110) and the fate of Carbon on crystalline Ni(100). Paulo Araujo, Daniela Mafra, Alfonso Reina, Young Cheol Shin, Ki Kang Kim, Mildred Dresselhaus, Jing Kong The growth of large area single-layer graphene (1-LG) is studied using ambient pressure CVD on single crystal Ni(111), Ni(110) and Ni(100). By varying both the furnace temperature in the range of 700 - 1100$^{\mathrm{o}}$C and the gas flow through the growth chamber, a uniform growth of high-quality 1-LG is obtained for Ni(111) and Ni(110), but only multilayer graphene (M-LG) growth could be obtained for Ni(100). The experimental results are interpreted to obtain the optimum combination of temperature and gas flow, and the results reported in this manuscript are interpreted through different thermodynamic mechanisms, such as diffusion, segregation and adsorption, which dictate the formation of different carbon structures over the different crystallographic directions of Ni. Characterization with optical microscopy, Raman spectroscopy and optical transmission accordingly support the experimental findings. [Preview Abstract] |
Tuesday, March 14, 2017 2:03PM - 2:15PM |
F30.00013: Intercalation and Etching of Graphene by Oxygen and Carbon Monoxide Tianbai Li Graphene (Gr), a one-atom thick sheet of sp2-bonded carbon, is a fascinating two-dimensional material with unique properties that shows great promise for diverse applications. There is evidence that contaminants attached to Gr can affect the electronic properties, but relatively little is known about how such species adsorb. The experiments performed here involve exposure of O2 and CO to Gr grown onto Ru(0001) via chemical vapor deposition. The materials are interrogated with a novel application of helium low energy ion scattering (LEIS). It is shown that O2 and CO both adsorb by intercalating between the Gr and the substrate. The intercalated oxygen desorbs when the sample is annealed to 700 K, which is a lower temperature than it desorbs from clean Ru. It is further shown that some of the carbon in Gr is etched during the desorption, which could affect the quality of Gr-based devices. CO adsorption is studied using isotopically labeled carbon so that LEIS can distinguish it from the Gr. A full layer of intercalated CO is oriented vertically, but the molecules can lie down horizontally underneath the Gr layer when excess CO is removed by annealing. [Preview Abstract] |
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