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.

Highly bendable high-mobility graphene field effect transistors with multi-finger embedded gates on flexible substrates

Abstract: A highly bendable, high mobility graphene field-effect transistor with embedded-gate structure is fabricated on commercial polyimide films. Multi-finger configuration consisting of 10 and 18 fingers is used to increase the current drivability. Bendability measurements for the device show that it is fully functional at the bending radius of down to 1.3mm. The shift in the dirac point is less than 0.6V, which is the result from the high uniformity of the grown graphene films and the simplified process minimizing the exposure of graphene to chemicals and the risk of chemical contamination. Plasma enhanced chemical vapor deposited silicon nitride is used as a capping layer to prevent contamination of the device from environments and provides robust protection over exposure to liquids.

Fabrication and measurement of suspended silicon carbide nanowire devices and deflection

Abstract: In this paper, we report the measurement of the deflection of β-SiC nanowires supported at both ends. Such wires hold promise as active elements in NEMS/MEMS devices. To ensure the stable mechanical clamping and electrical contacts between electrodes and nanowires, we have developed a method of metal deposition to improve the contacts. This method consists of multiple depositions at different angles in order to avoid the shadow effect and reduce the compressive residual stress. The improvement of the contacts was verified via SEM observation and electrical transport measurements. To suspend the nanowire, a dielectric layer underneath was removed, followed by critical point drying. The change of electrical resistance was measured when the suspended nanowires were deflected by either capillary forces arising from the surface tension or electrostatic forces.

Graphene/fluoropolymer hybrid materials with enhancement of all device properties for improved field-effect transistors

Abstract: We report on the substantial improvement of the electronic characteristics of field-effect transistors (FETs) based on chemical vapor deposition (CVD) graphene, reduced graphene oxide (RGO), and molybdenum disulfide (MoS2) by an interacting capping layer of appropriate amorphous or polycrystalline fluoropolymers. All the key 2-dimensional device properties are improved including mobilities, on-off current ratio, electron-hole transport symmetry, Dirac voltage, and reduced residual carrier density.

Impact of contact and access resistances in graphene field-effect transistors on quartz substrates for radio frequency applications

Abstract: High-frequency performance of graphene field-effect transistors (GFETs) has been limited largely by parasitic resistances, including contact resistance (RC) and access resistance (RA). Measurement of short-channel (500 nm) GFETs with short (200 nm) spin-on-doped source/drain access regions reveals negligible change in transit frequency (fT) after doping, as compared to ∼23% fT improvement for similarly sized undoped GFETs measured at low temperature, underscoring the impact of RC on high-frequency performance. DC measurements of undoped/doped short and long-channel GFETs highlight the increasing impact of RA for larger GFETs. Additionally, parasitic capacitances were minimized by device fabrication using graphene transferred onto low-capacitance quartz substrates.

Atomic scale engineering of metal-oxide-semiconductor photoelectrodes for energy harvesting application integrated with Graphene and Epitaxy SrTiO 3

Abstract: In this work, hydrogen production from water is demonstrated via a p-type silicon photocathode with a thin epitaxial strontium titanate, SrTiO3 (STO), as capping layer by molecular beam epitaxy. The advantages of using STO are the ideal conduction band alignment and perfect lattice match between single crystalline SrTiO3 and Si, so the photogenerated electrons can transport through the capping layer with a reduced recombination rate. The STO/p-Si photocathode exhibited a maximum photocurrent density and open circuit potential of 35 mA/cm2 and 450 mV, respectively. There was no observable decrease in performance after 10 hr operation in 0.5M H 2 SO 4 . We found the efficiency and performance were highly dependent on the size and spacing of the structured metal catalyst. Scaled down the metal catalysts feature size into nanometer region can greatly improve the efficiency. In addition, samples with graphene (Grahene/p-Si) as the lateral transport channel and capping layer shown an enhanced fill factor compared with that of STO/p-Si.

The rise of graphene

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.

Fast parallel algorithms for short-range molecular dynamics

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.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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。

Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

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.