Changgu Lee

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 q

Using friction force microscopy, we compared the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide (MoS2), niobium diselenide, and hexagonal boron nitride exfoliated onto a weakly adherent substrate (silicon oxide) to those of their bulk counterparts. Measurements down to single atomic sheets revealed that friction monotonically increased as the number of layers decreased for all four materials. Suspended graphene membranes showed the same trend, bu

Abstract We describe studies of the elastic properties and frictional characteristics of graphene samples of varying thickness using an atomic force microscope. For tensile testing, graphene is suspended over micron‐sized circular holes and indented by atomic force microscope (AFM) tips. Fitting of the force‐displacement curves yields the prestress and elastic stiffness, while comparison of the breaking force to simulation gives the ultimate strength, which is the highest measured for any materi

By plasma-enhanced chemical vapor deposition, a molybdenum disulfide (MoS2 ) thin film is synthesized directly on a wafer-scale plastic substrate at below 300 °C. The carrier mobility of the films is 3.74 cm(2) V(-1) s(-1) . Also, humidity is successfully detected with MoS2 -based sensors fabricated on the flexible substrate, which reveals its potential for flexible sensing devices.

Correction for 'Anomalous polarization dependence of Raman scattering and crystallographic orientation of black phosphorus' by Jungcheol Kim et al., Nanoscale, 2015, 7, 18708-18715, DOI: 10.1039/C5NR04349B.

The friction of graphene on various substrates, such as SiO2, h-BN, bulk-like graphene, and mica, was investigated to characterize the adhesion level between graphene and the underlying surface. The friction of graphene on SiO2 decreased with increasing thickness and converged around the penta-layers due to incomplete contact between the two surfaces. However, the friction of graphene on an atomically flat substrate, such as h-BN or bulk-like graphene, was low and comparable to that of bulk-like

We describe a method for synthesizing large-area and uniform molybdenum disulfide films, with control over the layer number, on insulating substrates using a gas phase sulfuric precursor (H2S) and a molybdenum metal source. The metal layer thickness was varied to effectively control the number of layers (2 to 12) present in the synthesized film. The films were grown on wafer-scale Si/SiO2 or quartz substrates and displayed excellent uniformity and a high crystallinity over the entire area. Thin

Heterostructures that combine graphene and transition metal dichalcogenides, such as MoS₂ , MoTe₂ , and WS₂ , have attracted attention due to their high performances in optoelectronic devices compared to homogeneous systems. Here, a photodevice based on a hybrid van der Waals heterostructure of rhenium disulfide (ReS₂ ) and graphene is fabricated using the stacking method. The device presents a remarkable ultrahigh photoresponsivity of 7 × 10<sup>5</su

Graphene oxide (GO) papers are candidates for structural materials in modern technology due to their high specific strength and stiffness. The relationship between their mechanical properties and structure needs to be systematically investigated before they can be applied to the broad range fields where they have potential. Herein, the mechanical properties of GO papers with various thicknesses (0.5–100 μm) are investigated using bulge and tensile test methods; this includes the Young's modulus,

Abstract Microscopic structures and magnetic properties are investigated for Fe 5− x GeTe 2 single crystal, recently discovered as a promising van der Waals (vdW) ferromagnet. An Fe atom (Fe(1)) located in the outermost Fe 5 Ge sublayer has two possible split‐sites which are either above or below the Ge atom. Scanning tunneling microscopy shows √3 × √3 superstructures which are attributed to the ordering of Fe(1) layer. The √3 × √3 superstructures have two different phases due to the symmetry of

The substitutional doping method is ideally suited to generating doped two-dimensional (2D) materials for practical device applications as it does not damage or destabilize such materials. However, recently reported substitutional doping techniques for 2D materials have given rise to discontinuities and low uniformities, which hamper the extension of such techniques to large-scale production. In the current work, we demonstrated uniform substitutional doping of monolayer MoS₂ in a 2 i

Direct contacts of a metal with atomically thin two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors have been found to suppress device performance by producing a high contact resistance. NbS₂ is a 2D TMDC and a conductor. It is expected to form ohmic contacts with 2D semiconductors because of its high work function and the van der Waals interface it forms with the semiconductor, with such an interface resulting in weak Fermi level pinning. Despite the usefulness

An ultraclean method to directly transfer a large-area MoS₂ film from the original growth substrate to a flexible substrate by using epoxy glue is developed. The transferred film is observed to be free of wrinkles and cracks and to be as smooth as the film synthesized on the original substrate.