Flexible energy storage devices 1Ϫ3 have many potential applications in portable electronic devices, 4Ϫ6 including roll-up display, electronic paper, stretchable integrated circuits, and wearable systems for personal multimedia, computing, or medical devices. Flexible supercapacitors are available with large power density, moderate energy density, good operational safety, and long cycling life and hence are highly desirable as a modern energy storage system. 7 A freestanding binder-free electrode with favorable mechanical strength and large capacitance is a vital component of a flexible supercapacitor. Although transition metal oxides and conducting polymers have been widely studied as supercapacitor electrode materials, only carbon-based materials have shown favorable flexibility and hence been promising as freestanding soft electrodes. Papers, films, and/or clothes made from carbon nanotubes/fibers have been demonstrated to be suitable as freestanding electrodes.2,8Ϫ13 Nevertheless, the less active surface of carbon materials always prevents them from high capacitance performance. The incorporation of an electrochemically active second phase in a carbonbased freestanding electrode can dramatically enhance the electrode capacitance.14 Graphene is an intriguing twodimensional carbon material and has attracted much research attention due to several breakthroughs in fundamental research and promising practical applications. 15Ϫ30Chemical modified graphene exhibits enormous active edges and oxygen functional groups. It has extraordinary electrochemical and mechanical properties comparable to or even better than carbon nanotubes. 21,26,27 Flexible papers with graphene sheet or graphene oxide sheet as sole building block have already been fabricated by flow-directed assembly. 16,25,31,32 Graphene paper presents excellent tensile modulus up to 35 GPa and room temperature electrical conductivity of 7200 S m Ϫ1. 25 These intriguing characteristics enable graphene paper as a freestanding electrode. Various conducting polymers have been widely studied as electrode materials for supercapacitors because of their high capacitance, easy production, and low cost. However, poor conductivity and weak flexibility of conducting polymers limit them from usage in high-performance flexible supercapacitors. It has been confirmed that graphene can enhance not only the electric conductivity of silica 18 but especially the mechanical strength of polymer composites. 21 This work is aimed to prepare graphene-conducting polymer composite paper as a flexible electrode combining the advantages of graphene paper (high

The development of spintronics devices relies on efficient generation of spin-polarized currents and their electric-field-controlled manipulation. While observation of exceptionally long spin relaxation lengths makes graphene an intriguing material for spintronics studies, electric field modulation of spin currents is almost impossible due to negligible intrinsic spin-orbit coupling of graphene. In this work, we create an artificial interface between monolayer graphene and few-layer semiconducting tungsten disulphide. In these devices, we observe that graphene acquires spin-orbit coupling up to 17 meV, three orders of magnitude higher than its intrinsic value, without modifying the structure of the graphene. The proximity spin-orbit coupling leads to the spin Hall effect even at room temperature, and opens the door to spin field effect transistors. We show that intrinsic defects in tungsten disulphide play an important role in this proximity effect and that graphene can act as a probe to detect defects in semiconducting surfaces.

The presence of direct bandgap and high mobility in semiconductor few-layer black phosphorus offers an attractive prospect for using this material in future two-dimensional electronic devices. However, creation of barrier-free contacts which is necessary to achieve high performance in black phosphorus-based devices is challenging and currently limits their potential for applications. Here, we characterize fully encapsulated ultrathin (down to bilayer) black phosphorus field effect transistors fabricated under inert gas conditions by utilizing graphene as source-drain electrodes and boron nitride as an encapsulation layer. The observation of a linear ISD-VSD behavior with negligible temperature dependence shows that graphene electrodes lead to barrier-free contacts, solving the issue of Schottky barrier limited transport in the technologically relevant two-terminal field-effect transistor geometry. Such one-atom-thick conformal source-drain electrodes also enable the black phosphorus surface to be sealed, to avoid rapid degradation, with the inert boron nitride encapsulating layer. This architecture, generally applicable for other sensitive two-dimensional crystals, results in air-stable, hysteresis-free transport characteristics.

Metallic glasses have a very high strength, hardness and elastic limit. However, they rarely show tensile ductility at room temperature and are considered quasi-brittle materials. Although these amorphous metals are capable of shear flow, severe plastic instability sets in at the onset of plastic deformation, which seems to be exclusively localized in extremely narrow shear bands approximately 10 nm in thickness. Using in situ tensile tests in a transmission electron microscope, we demonstrate radically different deformation behaviour for monolithic metallic-glass samples with dimensions of the order of 100 nm. Large tensile ductility in the range of 23-45% was observed, including significant uniform elongation and extensive necking or stable growth of the shear offset. This large plasticity in small-volume metallic-glass samples did not result from the branching/deflection of shear bands or nanocrystallization. These observations suggest that metallic glasses can plastically deform in a manner similar to their crystalline counterparts, via homogeneous and inhomogeneous flow without catastrophic failure. The sample-size effect discovered has implications for the application of metallic glasses in thin films and micro-devices, as well as for understanding the fundamental mechanical response of amorphous metals.

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