서동석 교수

Abstract A macroscopic carbon nanotube (CNT) sheet‐based heating element having flexible, stretchable, and damage‐tolerant features, and wide applicability in harsh environments, is introduced. Because of the intrinsic connection of extremely flexible CNT bundles throughout the sample by van der Waals interactions without use of a binder, the electrical resistance variation of the CNT sheet on elastomer heating element as a function of strain is completely suppressed to some extent, even when st

The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished.

Coil-structured carbon nanotube (CNT) yarns have recently attracted considerable attention. However, structural instability due to heavy twist insertion, and inherent hydrophobicity restrict its wider application. We report a twist-stable and hydrophilic coiled CNT yarn produced by the facile electrochemical oxidation (ECO) method. The ECO-treated coiled CNT yarn is prepared by applying low potentiostatic voltages (3.0-4.5 V vs Ag/AgCl) between the coiled CNT yarn and a counter electrode immerse

Abstract The marriage between a 2D layered material (2DLM) and a complex transition metal oxide (TMO) results in a variety of physical and chemical phenomena that cannot be achieved in either material alone. Interesting recent discoveries in systems such as graphene/SrTiO 3 , graphene/LaAlO 3 /SrTiO 3 , graphene/ferroelectric oxide, MoS 2 /SrTiO 3 , and FeSe/SrTiO 3 heterostructures include voltage scaling in field‐effect transistors, charge state coupling across an interface, quantum conductanc

We report on the demonstration of the active thermoelectric application to nanometer-scaled semiconductor devices. The thermoelectric heating already exists during programming in conventional phase change memory (PRAM) cells, which is only a minor supplement to Joule heating. Here, by rigorously designing devices, we have demonstrated an unprecedentedly high efficiency of PRAM, where the majority of the heat is supplied by the thermoelectric effect.

For transition metal dichalcogenides, the fluctuation of the channel current due to charged impurities is attributed to a large surface area and a thickness of a few nanometers. To investigate current variance at the interface of transistors, we obtain the low-frequency (LF) noise features of MoTe2 multilayer field-effect transistors with different dielectric environments. The LF noise properties are analyzed using the combined carrier mobility and carrier number fluctuation model which is addit

HfO2-based ferroelectric thin films deposited via atomic layer deposition have been extensively studied as promising candidates for next-generation ferroelectric devices. The conversion of an amorphous Hf1-xZrxO2 film to the ferroelectric phase (non-centrosymmetric orthorhombic phase) has been achieved through annealing using a post-thermal process. However, in this study, we present the first report of ferroelectricity of hafnium-zirconium-oxide (HZO) thin films deposited via atomic layer depos

A graphene Hall element (GHE) is an optimal system for a magnetic sensor because of its perfect two-dimensional (2-D) structure, high carrier mobility, and widely tunable carrier concentration. Even though several proof-of-concept devices have been proposed, manufacturing them by mechanical exfoliation of 2-D material or electron-beam lithography is of limited feasibility. Here, we demonstrate a high quality GHE array having a graphene on hexagonal-BN (h-BN) heterostructure, fabricated by photol

(STO) thin film is studied to understand the role of oxygen vacancies in determining the dielectric properties of STO. As the gate-voltage sweep range is gradually increased in the device, systematic generation and annihilation of oxygen vacancies, evidenced from the hysteretic conductance behavior in the graphene, are observed. Furthermore, based on the experimentally observed linear scaling relation between the effective capacitance and the voltage sweep range, a simple model is constructed to

Electrical characteristics of Ge2Sb2Te5 (GST) nanoparticles have been examined for a phase-change memory applications. The GST nanoparticles were generated by in situ pulsed laser ablation and their crystal structure formation was confirmed [H. R. Yoon et al., J. Non-Cryst. Solids 351, 3430 (2005)]. A stacked structure of the GST nanoparticles with 10nm of average diameter shows reversible nonvolatile switching characteristics between a high resistance state and a low resistance state as in the

The magnetoconductivity of two kinds of iodine doped helical polyacetylene, R- and S-polyacetylene, were investigated to understand the effect of the intrafibril and the interfibrillar interaction in the polyacetylene system. The zero-field resistivity ratio, ρr=ρ(1.2 K)/ρ(300 K), is comparable to that of stretch-oriented high-density polyacetylene film, which indicates the partial alignment of chains inside a polymer fiber. At low magnetic fields, the small negative component of magnetoconducti

Abstract Development of new types of optical components applicable to flexible and stretched substrates is essential for designing innovative display platforms for wearable and outdoor applications. Here, a novel polarizer based on highly aligned macroscopic carbon nanotube (CNT) sheets with flexibility, thermal stability, high polarization efficiency, and high transmittance is introduced. Since the conductive multiwalled CNTs are essentially held together by van der Waals forces, wire‐grid‐type

Abstract The recent discovery of a two-dimensional van der Waals magnet has paved the way for an enhanced understanding of two-dimensional magnetic systems. The development of appropriate heterostructures in this emerging class of materials is required as the next step towards applications. Here, we report on the electrical transport in monolayer graphene coupled with the two-dimensional ferromagnet Cr 2 Ge 2 Te 6 (CGT). Graphene that forms an interface with CGT is electron-doped owing to charge