Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session S36: Synthesis and Properties of 2D Materials and Nanoribbons |
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Sponsoring Units: DMP Chair: Jesse Thompson, University of Central Florida Room: LACC 410 |
Thursday, March 8, 2018 11:15AM - 11:27AM |
S36.00001: Ultrafast Epitaxial Growth of Metre-Sized Single-Crystal Graphene Xiaozhi Xu, Zhihong Zhang, Jichen Dong, Ding Yi, Li Lin, Jingjing Niu, Muhong Wu, Rongkang Yin, Mingqiang Li, Jingyuan Zhou, Shaoxin Wang, Junliang Sun, Xiaojie Duan, Peng Gao, Ying Jiang, Xiaosong Wu, Hailin Peng, Rodney Ruoff, Zhongfan Liu, Dapeng Yu, Enge Wang, Feng Ding, Kaihui Liu Graphene single crystal has become a promising material for next generation electronics and optoelectronics. In this talk I will introduce why we need to grow graphene faster and how fast we can achieve in our recently developed new technology. We present here the growth, in 20 min, of a graphene film of (5 × 50) cm2 dimension with >99% ultra-highly oriented grains. This growth was achieved by: (1) synthesis of metre-sized single-crystal Cu(111) foil as substrate; (2) epitaxial growth of graphene islands on the Cu(111) surface; (3) seamless merging of such graphene islands into a graphene film with high single crystallinity and (4) the ultrafast growth of graphene film. These achievements were realized by a temperature-gradient-driven annealing technique to produce single-crystal Cu(111) from industrial polycrystalline Cu foil and the marvelous effects of a continuous oxygen supply from an adjacent oxide. The as-synthesized graphene film, with very few misoriented grains (if any), has a mobility up to ~ 23,000 cm2 V-1 s-1 at 4 K and room temperature sheet resistance of 230 Ω/square. It is likely that this approach can be scaled up to achieve exceptionally large and high-quality graphene with single crystallinity, and thus realize various industrial-level applications at low cost. |
Thursday, March 8, 2018 11:27AM - 11:39AM |
S36.00002: Synthesis of Single Crystal Graphene by Chemical Vapor Deposition. Sajith Withanage, Rasanga Samaraweera, Tharanga Nanayakkara, U. Kushan Wijewardena, Annika Kriisa, Ramesh Mani Graphene growth by chemical vapor deposition (CVD) has attracted great attention since CVD is a relatively simple method that provides for very large-area graphene films [1]. However, the relatively low carrier mobility, issues associated with graphene transfer to a substrate, and the multigrain structure observed in CVD graphene, suggest the need for further research [2]. Here, we present results of a study of surface modified CVD growth of graphene on copper foil and limiting the nucleation using various methods. Thus, we detail the effect of controlling the nucleation and the surface properties of the starting copper foil on the size and the quality of relatively large sized single crystal graphene flakes. The graphene layers are characterized by various methods and the results are reported. [1] Q. Yu et al., Nature Materials 10, 443 (2011). [2] K. S. Novoselov et al., Nature 490, 192 (2012). |
Thursday, March 8, 2018 11:39AM - 11:51AM |
S36.00003: Metre-Sized Single-Crystal Graphene on Industrial Cu Foils Zhihong Zhang, Xiaozhi Xu, Enge Wang, Kaihui Liu Growth of single-crystal graphene (SCG) is the prerequisite of the high-end applications of graphene. However, state-of-the-art technique can only achieve inch-size SCG, far away from the real industrialization demand. In this talk the synthesis of a graphene film of (5×50) cm2 dimension with >99% ultra-highly oriented domains was presented [1]. We first transformed industrial polycrystalline Cu foils into single-crystal Cu(111) by thermal annealing using a temperature gradient driving technique. Then graphene domains were epitaxially grown on the Cu(111) substrate and seamlessly merged together to form a large SCG films. Combined with our ultrafast graphene growth technique [2], the graphene growth rate and the individual graphene domain size were increased obviously. Also, oxygen released from the oxide substrate at high temperature was helpful to further improve the domain alignment, which would greatly promote the quality of graphene films. This technique is very likely to be scaled up to achieve exceptionally large and high-quality graphene films, and thus realize various industrial-level applications at a low cost. |
Thursday, March 8, 2018 11:51AM - 12:03PM |
S36.00004: Single-Crystal Bilayer Graphene with Controlled Stacking from Ni-Cu Gradient Alloy Zhaoli Gao, Qicheng Zhang, Carl Naylor, Youngkuk Kim, Irfan Abidi, Jinglei Ping, Pedro Ducos, Jonathan Zauberman, Mengqiang Zhao, Andrew Rappe, Ying-Jun Wang, Zhengtang Luo, Li Ren, Alan Johnson Previously reported approaches for bilayer graphene (BLG) growth include flat growth substrates of Cu or Ni-Cu uniform alloys and “copper pocket” structures. Use of flat substrates has the advantage of being scalable, but the growth mechanism is either “surface limited” (for Cu) or carbon precipitation (for uniform Ni-Cu), which results in multi-crystalline BLG grains. For copper pockets, growth proceeds through a carbon back-diffusion mechanism, which leads to the formation of highly crystalline BLG but scaling of the copper pocket structure is expected to be difficult. Here we demonstrate a Ni-Cu gradient alloy that combines the advantages of these earlier methods: the substrate is flat, so easy to scale, while growth proceeds by a carbon back-diffusion mechanism leading to high-yield growth of BLG with high crystallinity. The BLG layer stacking was almost exclusively Bernal or twisted with an angle of 30 °, consistent with first principles calculations we conducted. Furthermore, we demonstrated scalable production of transistor arrays based single-crystal Bernal-stacked BLG with a bandgap that was tunable at room temperature. |
Thursday, March 8, 2018 12:03PM - 12:15PM |
S36.00005: Abstract Withdrawn
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Thursday, March 8, 2018 12:15PM - 12:27PM |
S36.00006: Selective Area Heteroepitaxial Growth of h-BN Micropatterns on Graphene Layers Hongseok Oh, Jiyoung Yun, Janghyun Jo, Hyun Hwi Lee, Miyoung Kim, Gyu-Chul Yi Two-dimensional (2D) layers and their heterostructures have great potential for novel electronic and optoelectronic devices due to their remarkable physical properties and interesting behaviors. Accordingly, these 2D nanomaterials have been used in transferable and flexible optoelectronic and electronic devices. Additionally, stacked heterostructures of hexagonal boron nitride (h-BN) and graphene have enabled the fabrication of high-performance electronic devices. Nevertheless, these stacked configurations are still limited by the ability to fabricate h-BN and graphene heterostructures at specific positions. It is crucial for this to be resolved to enable such heterostructures to be exploited as building blocks for fabricating integrated devices. |
Thursday, March 8, 2018 12:27PM - 12:39PM |
S36.00007: Epitaxial growth of continuous hexagonal boron nitride monolayer consisting of millimeter-size single crystal domains Hao Tian, yanwei He, Alireza Khanaki, Renjing Zheng, Wenhao Shi, Jianlin Liu Epitaxial hexagonal boron nitride (h-BN) two-dimensional thin films with large single-crystal domains can significantly reduce density of grain boundaries and improve the device performance. In this work, we report the growth of continuous h-BN monolayer with millimeter-size epitaxial single-crystal domains on carburized Ni substrates by treating Ni with acetylene prior to the growth of h-BN in a plasma-assisted MBE system. We show that the dissolution of carbon can help achieve exclusive h-BN monolayer. In addition, we systemically study the effect of different temperatures and carburization conditions on the morphology of h-BN films. Through the optimization of the growth parameters, single crystal domains on the order of 0.6 mm are achieved. Furthermore, centimeter-scale alignment of these h-BN domains has been observed. Further Electron Backscatter Diffraction (EBSD) studies reveal the epitaxial relationship between h-BN domains and Ni substrate. |
Thursday, March 8, 2018 12:39PM - 12:51PM |
S36.00008: Synthesis of Single-Layer h-BN Film on Cobalt Foil by Eliminating Nitrogen Intercalation Yanwei He, Hao Tian, Protik Das, Alireza Khanaki, Zhenjun Cui, Roger Lake, Jianlin Liu The growth mechanism of single- and multi-layer h-BN on Co foil was studied by means of source control and substrate carburization in our MBE system. We found that the edge-atom state and film/substrate interface distance play the key role in the formation of either single-layer h-BN film or multi-layer h-BN flakes. When ammonia is used as molecular source, the edge of as grown h-BN flake is terminated with hydrogen atom, which enables the diffusion of N atoms and NHx (x=1, 2) radicals into the interface of h-BN flake and substrate surface, leading to the multilayer growth from bottom. When nitrogen plasma is used as atomic source, however, the edge of as grown h-BN flake is bonded to substrate surface, thus, the gate for diffusion is closed, and upcoming nitrogen atoms are caught by active edge atoms, leading to the lateral growth. Nevertheless, we found that ad-layers can be formed in some areas where h-BN film grows across different Co grains and loses its epitaxial relationship to <111> surface, which results in large interface distance. By introducing certain amount of interstitial carbon into Co substrate, the interface distance is decreased so as to close the channel for diffusion, and eventually the growth of uniform single-layer h-BN film is achieved. |
Thursday, March 8, 2018 12:51PM - 1:03PM |
S36.00009: First principles studies of Carbon ring formation underneath of hexagonal boron nitride growth on Rh(111) Zahra Hooshmand Gharehbagh, Duy Le, Talat Rahman Hexagonal boron nitride (h-BN), grown on Rh(111) forms a Moiré pattern with elevated (rim) and depression (valley) areas.The presence of the native carbon impurities in Rh potentially gives rise to the formation of hexagonal carbon rings under every other rim area as suggested by recent experiments [1] and could lead to new structures and novel chemistry.Here, on the basis of Density Functional Theory (DFT) simulations with dispersion corrections, we show that these rings tend to grow in a manner in which the center of each ring is placed on top of the Rh atom. These rings grow next to each other and form islands which are separated from each other by an equal distance while the BN monolayer remains untouched. Our simulations of Scanning Tunneling Microscope (STM) images from this structure, in good agreement with experimental data for number of rings from 3 to 5.The calculations of local variations in work function also show that these variations become more pronounced by growth of islands.This results show that by control of the concentration of local impurities underneath the rim areas in BN, the chemical properties are modified and the monolayer could be engineered for interesting chemical reactions. [1] Koslowski et al. Private communication. |
Thursday, March 8, 2018 1:03PM - 1:15PM |
S36.00010: Decoration of Graphene Grown Using Hot Filimant Chemical Vapor Deposition Tina Brower-Thomas Graphene has been grown by hot filament chemcial vapor depostition on SiC. The graphene has been characterized by Raman, Scanning Probe Microscopy and Electron Microscopy. Graphene on Si, TEM grids and SiC have been decoarted using transition metals and characterized. Shifts in Raman are shown to depend on traniisition metal used for decoration. This talk will discuss preliminary findings and implcations of results. |
Thursday, March 8, 2018 1:15PM - 1:27PM |
S36.00011: Influence of Substrate on the Epitaxial Graphene on SiC Yiran Hu, Vladimir Prudkovskiy, Dogukan Deniz, Yue Hu, Jean-Philippe Turmaud, James Gigliotti, Lei Ma, Claire Berger, Walt de Heer Epitaxial graphene on SiC has been an active and promising research field for graphene electronics. The sidewall graphene nanoribbons (GNR) directly grown on the Si-face of SiC surface steps are especially attractive, showing exceptional room temperature single channel ballistic transport [1]. Despite the keen interest in the sidewall GNRs, understanding of the influence of the nonpolar SiC facets on which they grow is still lacking. Here we report on the investigation of graphene grown on non-polar facets and substrate effects on the graphene growth and properties. Various types of non-polar facets have been used. The resulting graphene was extensively characterized by Raman spectroscopy, atomic force microscopy, low energy electron diffraction and various other tools. |
Thursday, March 8, 2018 1:27PM - 1:39PM |
S36.00012: Networks of Graphene Nanoribbons and Nanosheets Formed in Metals by the Electrocharging Assisted Process Lourdes Salamanca-Riba, Xiaoxiao Ge, Romaine Isaacs, Daniel Cole, Manfred Wuttig, Karen Gaskell, Liangbing Hu, Oded Rabin, Balu Balachandran The incorporation of carbon nanostructures, such as graphene and carbon nanotubes, in the lattice of metals is desirable to take advantage of the superior mechanical and electrical properties of these graphitic nanostructures and the high density of electrons in metals. There have been numerous attempts to create composites of metals, such as copper or aluminum, with carbon nanostructures. These methods frequently require several steps and in aluminum produce the undesirable compound Al4C3. We use electrocharging assisted process which creates graphene nanoribbons and nanosheets in a metal by the application of a high DC current of ~150 A to a mixture of the liquid metal and particles of activated carbon. The graphitic structures bond with atoms in the metal making the composite very stable. Raman scattering, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy indicate sp2 bonding of the carbon and TEM images show graphene nanoribbons and nanosheets in the lattice of the metal. The electrical conductivity of Al covetic with 3 wt % C increased by ~20% and the thermal conductivity of copper with ~3 wt % C increased by ~13%. Films of Cu with C are more transparent and resistant to oxidation than pure copper films. |
Thursday, March 8, 2018 1:39PM - 1:51PM |
S36.00013: Armchair Graphene Nanoribbons Grown Directly on Germanium with High Conductance and On/Off Ratio Robert Jacobberger, Michael Arnold The chemical vapor deposition of graphene on Ge(001) can result in highly anisotropic crystal growth, enabling the facile synthesis of oriented, quasi-one-dimensional, graphene nanoribbons that are semiconducting, whereas continuous two-dimensional graphene is semimetallic. This bottom-up synthesis yields sub-10 nm ribbons with predominately smooth armchair edges, and overcomes long-standing challenges that have limited top-down ribbon fabrication (e.g., poor resolution and disordered ribbon edges). Here, we characterize the charge transport properties of nanoribbons with sub-10 nm widths grown on Ge(001). We show that nanoribbons synthesized via this technique can simultaneously achieve high on-state conductance of 5 μS and high on/off conductance ratio of 2×104 in field-effect transistors, favorably comparing to or exceeding the performance of ribbons fabricated by other approaches. These charge transport measurements demonstrate that if the positioning and width uniformity of the ribbons are improved, for example via the use of nanoscale seeds to template growth, the direct synthesis of nanoribbons on Ge(001) could provide a scalable route toward the practical realization of high-performance semiconducting graphene technologies. |
Thursday, March 8, 2018 1:51PM - 2:03PM |
S36.00014: Seed-Mediated Growth of Unidirectional Armchair Graphene Nanoribbon Arrays on Germanium Austin Way, Robert Jacobberger, Michael Arnold Graphene nanoribbons with sub-10 nm widths and smooth armchair edges exhibit promising electrical and thermal properties and can have bandgaps sufficiently large for semiconductor electronics. However, development of nanoribbons has been hindered by difficulties in producing ribbons with a high degree of structural precision in a scalable manner. It was recently shown that CVD growth on Ge(001) can directly yield long, semiconducting graphene nanoribbons with smooth armchair edges. However, the mechanisms that give rise to the anisotropic crystal growth are not understood, and the nanoribbons stochastically nucleate at random locations and times, causing width and bandgap polydispersity. Here, we study the seed-mediated growth of graphene nanoribbons on Ge(001). We find that high aspect ratio ribbons evolve when the armchair direction of the seeds is parallel to Ge<110>, while the aspect ratio decreases as these two directions become misaligned. We show that seeding enables control over nanoribbon position, reduced polydispersity, and the fabrication of unidirectional, nanoribbon arrays. Provided that dense arrays of sub-10 nm can be fabricated, this seed-mediated growth promises to provide a route toward the scalable integration of nanoribbons into semiconductor electronics. |
Thursday, March 8, 2018 2:03PM - 2:15PM |
S36.00015: High-Yield Single-Step Catalytic Growth of Graphene Nanostripes by Plasma Enhanced Chemical Vapor Deposition Chen-Chih Hsu, Jacob Bagley, Marcus Teague, Wei-Shiuan Tseng, James Tour, Nai-Chang Yeh We report a single-step growth process of graphene nanostripes (GNSPs) by adding certain substituted aromatics as precursors during the PECVD. Without any active heating and by using low plasma power (≤ 60 W), we are able to grow GNSPs vertically with high yields up to (13 ± 4) g/m2 in 20 minutes. The morphology, electronic properties, width and yields of the GNSPs can be controlled by the growth parameters (e.g., the species of seeding molecules, compositions and flow rates of the gases, plasma power, and the growth time). Studies of the Raman spectra, SEM and TEM images, EDX, and electrical conductivity of these GNSPs as functions of the growth parameters confirm high-quality GNSPs with electrical mobility ~ 104 cm2/V-s. Together with the residual gas analyzer spectra and optical emission spectroscopy taken during PECVD growth, we propose a growth and branching mechanism of GNSPs. Our findings open up a pathway to inexpensive mass production of high-quality GNSPs for large-scale applications such as in supercapacitors and lithium-ion batteries. |
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