1,529 research outputs found
Quasi-freestanding and single-atom thick layer of hexagonal boron nitride as a substrate for graphene synthesis
We demonstrate that freeing a single-atom thick layer of hexagonal boron
nitride (hbn) from tight chemical bonding to a Ni(111) thin film grown on a
W(110) substrate can be achieved by intercalation of Au atoms into the
interface. This process has been systematically investigated using
angle-resolved photoemission spectroscopy, X-ray photoemission and absorption
techniques. It has been demonstrated that the transition of the hbn layer from
the "rigid" into the "quasi-freestanding" state is accompanied by a change of
its lattice constant. Using chemical vapor deposition, graphene has been
successfully synthesized on the insulating, quasi-freestanding hbn monolayer.
We anticipate that the in situ synthesized weakly interacting graphene/hbn
double layered system could be further developed for technological applications
and may provide perspectives for further inquiry into the unusual electronic
properties of graphene.Comment: in print in Phys. Rev.
Recommended from our members
Controlled assembly of graphene-capped nickel, cobalt and iron silicides
In-situ dendrite/metallic glass matrix composites (MGMCs) with a composition of Ti46Zr20V12Cu5Be17 exhibit ultimate tensile strength of 1510 MPa and fracture strain of about 7.6%. A tensile deformation model is established, based on the five-stage classification: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (yield platform), (4) plastic-plastic (work hardening), and (5) plastic-plastic (softening) stages, analogous to the tensile behavior of common carbon steels. The constitutive relations strongly elucidate the tensile deformation mechanism. In parallel, the simulation results by a finite-element method (FEM) are in good agreement with the experimental findings and theoretical calculations. The present study gives a mathematical model to clarify the work-hardening behavior of dendrites and softening of the amorphous matrix. Furthermore, the model can be employed to simulate the tensile behavior of in-situ dendrite/MGMCs
Математическая модель шероховатости обрабатываемой поверхности при сверхскоростном фрезеровании
У статті розглядається новий підхід до вирішення проблеми знаходження математичної моделі шорсткості обробленої поверхні при надшвидкісному фрезеруванні.The article deals with the new approach to
solving a problem of finding machined surface
roughness mathematical model at superhigh-
speed milling.В статье рассматривается новый подход к
решению проблемы нахождения математической модели обработанной поверхности при сверхскоростном фрезеровании
Прогнозирование распределения тепла в заготовке при сверхскоростном фрезeровании
У статті розглядається новий підхід до рішення проблеми прогнозу розподілу тепла в перетинах заготівки при надшвидкісному фрезеруванні.In work state the new solution method of the
problem of the prognosis of the thermal distribution in cut of the workpiece.В статьe рассматривается новый подход к
решению проблемы прогноза распределения тепла в сечениях заготовки
The Fire Simulation in a Road Tunnel
Fire behaviour, especially its interaction with ventilation system in tunnels, is still a challenging issue for road tunnel
designers .This paper presents the results of a study investigating the influence of a road tunnel ventilation system, on
conventional fires. For this purpose, a 25 MW fire corresponding to a conventional fire in a road tunnel was
simulated using 2D numerical modelling, for transient viscous multi-component gas at low Mach numbers to study
smoke and heat propagation within a road tunnel under fire .Complete Navier-Stocks and Reynolds equations were
solved using developed algorithm of numerical modelling .The results from a series of calculations were compared
with results of experimental researches to examine the accuracy and stability of the calculations .The comparisons
showed that the algorithm provided a good description of physical processes in selected class of flow. It was also
concluded that calculation accuracy is not lower than those obtained from established simulation software programs .
The stability and good convergence of the algorithm was confirmed by separate calculations with different grid
patterns for the tunnel under consideration .The results revealed that the temperature at tunnel wall may rise up to
900oC. The concentration of smoke may also increase up to 95 %with a burning truck .Results were applied to assess
the ventilation system designed for a new long road tunnel in case of fire .The results from the study along with other
information were applied to assess the designed ventilation system and to establish the suitable fire fighting and
rescue plan
Atomically precise semiconductor-graphene and hBN interfaces by Ge intercalation
The full exploration of the potential, which graphene offers to nanoelectronics requires its integration into semiconductor technology. So far the real-world applications are limited by the ability to concomitantly achieve large single-crystalline domains on dielectrics and semiconductors and to tailor the interfaces between them. Here we show a new direct bottom-up method for the fabrication of high-quality atomically precise interfaces between 2D materials, like graphene and hexagonal boron nitride (hBN), and classical semiconductor via Ge intercalation. Using angle-resolved photoemission spectroscopy and complementary DFT modelling we observed for the first time that epitaxially grown graphene with the Ge monolayer underneath demonstrates Dirac Fermions unaffected by the substrate as well as an unperturbed electronic band structure of hBN. This approach provides the intrinsic relativistic 2D electron gas towards integration in semiconductor technology. Hence, these new interfaces are a promising path for the integration of graphene and hBN into state-of-the-art semiconductor technology
Insight into the electronic structure of the centrosymmetric skyrmion magnet GdRuSi
The discovery of a square magnetic-skyrmion lattice in GdRuSi, with
the smallest so far found skyrmion diameter and without a geometrically
frustrated lattice, has attracted significant attention, particularly for
potential applications in memory devices and quantum computing. In this work,
we present a comprehensive study of surface and bulk electronic structures of
GdRuSi by utilizing momentum-resolved photoemission (ARPES)
measurements and first-principles calculations. We show how the electronic
structure evolves during the antiferromagnetic transition when a peculiar
helical order of 4 magnetic moments within the Gd layers sets in. A nice
agreement of the ARPES-derived electronic structure with the calculated one has
allowed us to characterize the features of the Fermi surface (FS), unveil the
nested region along the at the corner of the 3D FS, and reveal their
orbital compositions. Our findings suggest that the
Ruderman-Kittel-Kasuya-Yosida interaction plays a decisive role in stabilizing
the spiral-like order of Gd 4 moments responsible for the skyrmion physics
in GdRuSi. Our results provide a deeper understanding of electronic and
magnetic properties of this material, which is crucial for predicting and
developing novel skyrmion-based devices.Comment: 13 pages, 8 figure
Variation of the character of spin-orbit interaction by Pt intercalation underneath graphene on Ir(111)
The modification of the graphene spin structure is of interest for novel possibilities of application of graphene in spintronics. The most exciting of them demand not only high value of spin-orbit splitting of the graphene states, but non-Rashba behavior of the splitting and spatial modulation of the spin-orbit interaction. In this work we study the spin and electronic structure of graphene on Ir(111) with intercalated Pt monolayer. Pt interlayer does not change the 9.3×9.3 superlattice of graphene, while the spin structure of the Dirac cone becomes modified. It is shown that the Rashba splitting of the π state is reduced, while hybridization of the graphene and substrate states leads to a spin-dependent avoided-crossing effect near the Fermi level. Such a variation of spin-orbit interaction combined with the superlattice effects can induce a topological phase in graphene
Observation of a universal donor-dependent vibrational mode in graphene
Electron-phonon coupling and the emergence of superconductivity in intercalated graphite have been studied extensively. Yet, phonon-mediated superconductivity has never been observed in the 2D equivalent of these materials, doped monolayer graphene. Here we perform angle-resolved photoemission spectroscopy to try to find an electron donor for graphene that is capable of inducing strong electron-phonon coupling and superconductivity. We examine the electron donor species Cs, Rb, K, Na, Li, Ca and for each we determine the full electronic band structure, the Eliashberg function and the superconducting critical temperature Tc from the spectral function. An unexpected low-energy peak appears for all dopants with an energy and intensity that depend on the dopant atom. We show that this peak is the result of a dopant-related vibration. The low energy and high intensity of this peak are crucially important for achieving superconductivity, with Ca being the most promising candidate for realizing superconductivity in graphene
Ensuring safe descend of reusable rocket stages - Numerical simulation and experiments on subsonic turbulent air flow around a semi-circular cylinder at zero angle of attack and moderate Reynolds number
© 2017. Two-dimensional flow around semi-circular cylinder at zero angle of attack and at Re = 50000 during the self-oscillatory regime has been extensively studied within the URANS method with the use of different-structure grids (multiblock, structured overlapping, unstructured composite), the SST turbulence model and its versions (1993) and (2003) considering the streamline curvature influence modified within the Rodi-Leschziner-Isaev approach and numerical different-approximation methods realized in two codes (VP2/3, Fluent). Experiments have been made on flow around a semi-circular cylinder in the wind tunnel of the Lomonosov Moscow State University, Institute of Mechanics to obtain data for verification of numerical predictions. The double-mode character of a periodic time history of a drag force caused by a periodically forming and disappearing jet flap and acting upon a body is explained. With increasing compressibility at a Mach number ranging from 0 to 0.5, it is observed that periodic flow around the semi-circular cylinder is restructured, and the time history of the drag force acting upon it is described by a dependence close to a sinusoidal one. It is found that, as the Mach number is increased, pressure field distortions in the form of concentric cylindrical waves propagating from the semi-circular cylinder and the vortex street behind it grow over the infrasonic range
- …