Joo-Hoon Kang

Solution dispersions of two-dimensional (2D) black phosphorus (BP)--often referred to as phosphorene--are achieved by solvent exfoliation. These pristine, electronic-grade BP dispersions are produced with anhydrous organic solvents in a sealed-tip ultrasonication system, which circumvents BP degradation that would otherwise occur via solvated O2 or H2O. Among conventional solvents, N-methylpyrrolidone (NMP) is found to provide stable, highly concentrated (∼0.4 mg/mL) BP dispersions. Atomic force

Understanding and exploiting the remarkable optical and electronic properties of phosphorene require mass production methods that avoid chemical degradation. Although solution-based strategies have been developed for scalable exfoliation of black phosphorus, these techniques have thus far used anhydrous organic solvents in an effort to minimize exposure to known oxidants, but at the cost of limited exfoliation yield and flake size distribution. Here, we present an alternative phosphorene product

Exfoliation of single-layer graphene from bulk graphite and the subsequent discovery of exotic physics and emergent phenomena in the atomically thin limit has motivated the isolation of other two-dimensional (2D) layered nanomaterials. Early work on isolated 2D nanomaterial flakes has revealed a broad range of unique physical and chemical properties with potential utility in diverse applications. For example, the electronic and optical properties of 2D nanomaterials depend strongly on atomic-sca

octahedra tilting and the organic chain disordering, which results in bandgap decrease. This study indicates that careful heat management under LED operation is a key factor to maintain the sharp and intense emission.

The recent advancements in multivalued logic gates represent a rapid paradigm shift in semiconductor technology toward a new era of hyper Moore's law. Particularly, the significant evolution of materials is guiding multivalued logic systems toward a breakthrough gradually, whereby they are transcending the limits of conventional binary logic systems in terms of all the essential figures of merit, i.e., power dissipation, operating speed, circuit complexity, and, of course, the level of the integ

Abstract Layered indium selenide (InSe) presents unique properties for high‐performance electronic and optoelectronic device applications. However, efforts to process InSe using traditional liquid phase exfoliation methods based on surfactant‐assisted aqueous dispersions or organic solvents with high boiling points compromise electronic properties due to residual surface contamination and chemical degradation. Here, these limitations are overcome by utilizing a surfactant‐free, low boiling point

2D van der Waals (vdW) materials have been considered as potential building blocks for use in fundamental elements of electronic and optoelectronic devices, such as electrodes, channels, and dielectrics, because of their diverse and remarkable electrical properties. Furthermore, two or more building blocks of different electronic types can be stacked vertically to generate vdW heterostructures with desired electrical behaviors. However, such fundamental approaches cannot directly be applied prac

Abstract Inkjet printing is a cost-effective and scalable way to assemble colloidal materials into desired patterns in a vacuum- and lithography-free manner. Two-dimensional (2D) nanosheets are a promising material category for printed electronics because of their compatibility with solution processing for stable ink formulations as well as a wide range of electronic types from metal, semiconductor to insulator. Furthermore, their dangling bond-free surface enables atomically thin, electronicall

Chemical vapor deposition (CVD) using liquid-phase precursors has emerged as a viable technique for synthesizing uniform large-area transition metal dichalcogenide (TMD) thin films. However, the liquid-phase precursor-assisted growth process typically suffers from small-sized grains and unreacted transition metal precursor remainders, resulting in lower-quality TMDs. Moreover, synthesizing large-area TMD films with a monolayer thickness is also quite challenging. Herein, we successfully synthesi

The role of the interface roughness of Bi-Te core/shell nanowires is reported in reducing lattice thermal conductivity, which are prepared by on-film formation of nanowire (OFF-ON) that is capable of growing high-quality single-crystalline Bi nanowires, and by the subsequent sputtering of Te onto the Bi nanowires. The rough interface Bi-Te core/shell nanowires exhibit lower thermal conductivities than that of smooth interface counterparts, while electrical conductivities for these two types of n

Using scalable solution processing, layered gallium telluride (GaTe) nanoflake dispersions are produced in surfactant-free, low-boiling-point, water–ethanol cosolvent mixtures. During exfoliation, chemical degradation of the ambient-reactive GaTe crystals is minimized by using deoxygenated solvents in a sealed tip ultrasonication system. The structural and chemical integrity of the solution-processed GaTe nanoflakes is subsequently confirmed with a comprehensive suite of microscopic and spectros

Multi-valued logic gates are demonstrated on solution-processed molybdenum disulfide (MoS₂) thin films. A simple chemical doping process is added to the conventional transistor fabrication procedure to locally increase the work function of MoS₂ by decreasing sulfur vacancies. The resulting device exhibits pseudo-heterojunctions comprising as-processed MoS₂ and chemically treated MoS₂ (c-MoS₂). The energy-band misalignment of MoS₂

Isopycnic density gradient ultracentrifugation (iDGU) has been widely applied to sort nanomaterials by their physical and electronic structure. However, the commonly used density-gradient medium iodixanol has a finite maximum buoyant density that prevents the use of iDGU for high-density nanomaterials. Here, we overcome this limit by adding cesium chloride (CsCl) to iodixanol, thus increasing its maximum buoyant density to the point where the high-density two-dimensional nanomaterial rhenium dis