Young Hee Lee

Recent advances in atomically thin two-dimensional transition metal dichalcogenides (2D TMDs) have led to a variety of promising technologies for nanoelectronics, photonics, sensing, energy storage, and opto-electronics, to name a few. This article reviews the recent progress in 2D materials beyond graphene and includes mainly transition metal dichalcogenides (TMDs) (e.g. MoS 2 , WS 2 , MoSe 2 , and WSe 2 ). These materials are finding niche applications for next-generation electronics and optoe

Abstract The conductivity of graphite oxide films is modulated using reducing agents. It is found that the sheet resistance of graphite oxide film reduced using sodium borohydride (NaBH 4 ) is much lower than that of films reduced using hydrazine (N 2 H 4 ). This is attributed to the formation of CN groups in the N 2 H 4 case, which may act as donors compensating the hole carriers in reduced graphite oxide. In the case of NaBH 4 reduction, the interlayer distance is first slightly expanded by t

Artificial van der Waals heterostructures with two-dimensional (2D) atomic crystals are promising as an active channel or as a buffer contact layer for next-generation devices. However, genuine 2D heterostructure devices remain limited because of impurity-involved transfer process and metastable and inhomogeneous heterostructure formation. We used laser-induced phase patterning, a polymorph engineering, to fabricate an ohmic heterophase homojunction between semiconducting hexagonal (2H) and meta

Large-area, few-layer graphene is grown on a poly-nickel substrate using optimized CVD conditions. High temperature, short growth time, and an optimal gas mixing ratio (C2H2/H2 = 2/45) are found to be necessary to synthesize highly crystalline few-layer grapheme, which may find applications in electronic devices. The wrinkles that are observed under all growth conditions are proposed to be formed by two processes.

Asymmetric supercapacitors with high energy density are fabricated using a self‐assembled reduced graphene oxide (RGO)/MnO 2 (GrMnO 2 ) composite as a positive electrode and a RGO/MoO 3 (GrMoO 3 ) composite as a negative electrode in safe aqueous Na 2 SO 4 electrolyte. The operation voltage is maximized by choosing two metal oxides with the largest work function difference. Because of the synergistic effects of highly conductive graphene and highly pseudocapacitive metal oxides, the hybrid nanos

Supercapacitors are one of the key devices for energy-storage applications. They have energy densities much higher than those of conventional capacitors and possess much better power delivery capabilities than batteries. This makes them unique devices that can outperform both batteries and conventional capacitors under special circumstances. Nanocarbons are the main electrode materials for supercapacitors. Abundant sources of nanocarbons and facile processes of modification have led to the fabri

Seamless stitching of graphene domains on polished copper (111) is proved clearly not only at atomic scale by scanning tunnelling microscopy (STM) and transmission electron micoscopy (TEM), but also at the macroscale by optical microscopy after UV-treatment. Using this concept of seamless stitching, synthesis of 6 cm × 3 cm monocrystalline graphene without grain boundaries on polished copper (111) foil is possible, which is only limited by the chamber size.

Transition metal dichalcogenides are layered materials which are composed of transition metals and chalcogens of the group VIA in a 1:2 ratio. These layered materials have been extensively investigated over synthesis and optical and electrical properties for several decades. It can be insulators, semiconductors, or metals revealing all types of condensed matter properties from a magnetic lattice distorted to superconducting characteristics. Some of these also feature the topological manner. Inst

We propose a catalytic growth mechanism of single-wall carbon nanotubes based on density functional total energy calculations. Our results indicate nanotubes with an ``armchair'' edge to be energetically favored over ``zigzag'' nanotubes. We also suggest that highly mobile Ni catalyst atoms adsorb at the growing edge of the nanotube, where they catalyze the continuing assembly of hexagons from carbon feedstock diffusing along the nanotube wall. In a concerted exchange mechanism, Ni atoms anneal

A rapidly developing market for portable electronic devices and hybrid electrical vehicles requires an urgent supply of mature energy-storage systems. As a result, lithium-ion batteries and electrochemical capacitors have lately attracted broad attention. Nevertheless, it is well known that both devices have their own drawbacks. With the fast development of nanoscience and nanotechnology, various structures and materials have been proposed to overcome the deficiencies of both devices to improve

Abstract In spite of recent successful demonstrations of flexible and transparent graphene heaters, the underlying heat‐transfer mechanism is not understood due to the complexity of the heating system. Here, graphene/glass defoggers are fabricated and the dynamic response of the temperature as a function of input electrical power is measured. The graphene/glass defoggers reveal shorter response times than Cr/glass defoggers. Furthermore, the saturated temperature of the graphene/glass defoggers