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Rodney S. Ruoff

Bio: Rodney S. Ruoff is an academic researcher from Ulsan National Institute of Science and Technology. The author has contributed to research in topics: Graphene & Graphene oxide paper. The author has an hindex of 164, co-authored 666 publications receiving 194902 citations. Previous affiliations of Rodney S. Ruoff include Texas State University & North Carolina State University.


Papers
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TL;DR: In this article, the authors show that copper with an oxidized surface can act as a self-cleaning substrate for graphene growth by chemical vapor deposition (CVD), such as rinsing with acetone, nitric, and acetic acid, and high temperature hydrogen annealing.
Abstract: Commonly used techniques for cleaning copper substrates before graphene growth via chemical vapor deposition (CVD), such as rinsing with acetone, nitric, and acetic acid, and high temperature hydrogen annealing still leave residual adventitious carbon on the copper surface. This residual carbon promotes graphene nucleation and leads to higher nucleation density. We find that copper with an oxidized surface can act as a self-cleaning substrate for graphene growth by CVD. Under vacuum conditions, copper oxide thermally decomposes, releasing oxygen from the substrate surface. The released oxygen reacts with the carbon residues on the copper surface and forms volatile carbon monoxide and carbon dioxide, leaving a clean copper surface free of carbon for large-area graphene growth. Using oxidized electropolished copper foil leads to a reduction in graphene nucleation density by over a factor of 1000 when compared to using chemically cleaned oxygen free copper foil.

57 citations

Posted Content
TL;DR: In this article, the conversion of multilayer graphenes into sp^3-bonded carbon films on metal surfaces is indicated through first-principles computations.
Abstract: The conversion of multilayer graphenes into sp^3-bonded carbon films on metal surfaces (through hydrogenation or fluorination of the outer surface of the top graphene layer) is indicated through first-principles computations. The main driving force for this conversion is the hybridization between carbon sp^3 orbitals and metal surface dz^2 orbitals. The induced electronic gap states in the carbon layers are confined in a region within 0.5 nm of the metal surface. Whether the conversion occurs depend on the fraction of hydrogenated (fluorinated) C atoms and on the number of stacked graphene layers. In the analysis of the Eliashberg spectral functions for the sp^3 carbon films on diamagnetic metals, the strong covalent metal-sp^3 carbon bonds induce soft phonon modes that predominantly contribute to large electron-phonon couplings, suggesting the possibility of phonon-mediated superconductivity. Our results suggest a route to experimental realization of large-area ultrathin sp^3-bonded carbon films on metal surfaces.

57 citations

Journal ArticleDOI
14 Jun 2017
TL;DR: In this article, the residual oxygen and/or air play crucial roles in the growth of hexagonal boron nitride (h-BN) films on Ni foil 'enclosures'.
Abstract: We show that in a low-pressure chemical vapor deposition (CVD) system, the residual oxygen and/or air play a crucial role in the mechanism of the growth of hexagonal boron nitride (h-BN) films on Ni foil 'enclosures'. Hexagonal-BN films grow on the Ni foil surface via the formation of an intermediate boric-oxide (BOx) phase followed by a thermal reduction of the BOx by a carbon source (either amorphous carbon powder or methane), leading to the formation of single- and bi-layer h-BN. Low energy electron microscopy (LEEM) and diffraction (LEED) were used to map the number of layers over large areas; Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the structure and physical quality of the ultra-thin h-BN film. The growth procedure reported here leads to a better understanding and control of the synthesis of ultra-thin h-BN films.

57 citations

Journal ArticleDOI
15 May 2009
TL;DR: In this article, a method to grow large-area graphene films on Cu foils and graphene transfer methods to other substrates was reported, and the transferred graphene films were characterized by optical, scanning and transmission electron microscopy, Raman and UV-VIS spectroscopy, and four point probe electrical measurements.
Abstract: Graphene and few-layer graphene films exhibit unique properties and show promise as electronic devices as well as for passive applications. A significant challenge however is the synthesis of large area graphene and/or multilayer films. A method that is showing promise is the growth of graphene on metal substrates by chemical vapor deposition. In this paper we report on a method to grow large-area graphene films on Cu foils and graphene transfer methods to other substrates. The transferred graphene films were characterized by optical, scanning and transmission electron microscopy, Raman and UV-VIS spectroscopy, and four-point probe electrical measurements. The data shows that graphene can be grown directly on Cu substrates by chemical vapor deposition. The graphene films transferred to SiO2/Si substrates show low defects as determined by the near absence of the “D” band at 1350 cm -1 in the Raman spectrum. In addition, the films were found to have high optical transmittance and electrical conductivity.

56 citations

Journal ArticleDOI
TL;DR: In this article, first-principles modeling of water oxidation over various graphene systems, such as nitrogen-doped graphene; graphene monolayers on iron, nickel, and copper surfaces; and bi-and trilayer graphene on copper surfaces, was presented.
Abstract: We present first-principles modeling of water oxidation over various graphene systems, such as nitrogen-doped graphene; graphene monolayers on iron, nickel, and copper surfaces; and bi- and trilayer graphene on copper surfaces. It is shown that nitrogen-doped graphene and graphene over copper are better for this reaction than those over platinum at temperatures below 100 °C. Bi- and trilayer graphene on copper have catalytic properties similar to those of a monolayer on copper.

56 citations


Cited by
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TL;DR: Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena can now be mimicked and tested in table-top experiments.
Abstract: Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

35,293 citations

01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
Changgu Lee1, Xiaoding Wei1, Jeffrey W. Kysar1, James Hone1, James Hone2 
18 Jul 2008-Science
TL;DR: Graphene is established as the strongest material ever measured, and atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.
Abstract: We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

18,008 citations