김규태 교수

Diagnosing of the interface quality and the interactions between insulators and semiconductors is significant to achieve the high performance of nanodevices. Herein, low-frequency noise (LFN) in mechanically exfoliated multilayer molybdenum disulfide (MoS2) (~11.3 nm-thick) field-effect transistors with back-gate control was characterized with and without an Al2O3 high-k passivation layer. The carrier number fluctuation (CNF) model associated with trapping/detrapping the charge carriers at the i

A simple and general technique for producing a suspended nanofiber has been developed using coordinate markers and a sacrificial layer of poly(methylmethacrylate). The simple procedure does not involve etching processes or chemical vapor deposition and makes it easier to investigate the physical properties of nanofibers in a suspended configuration. As a demonstration, a suspended carbon nanotube rope was fabricated and Young’s modulus was determined to be 0.4 TPa from the force calibration of a

The thermoelectric power (TEP) of single walled carbon nanotube (SWCNT) thin films in pure metallic SWCNT (m-SWCNT) and pure semiconducting SWCNT (s-SWCNT) networks as well as in m- and s-SWCNT mixtures is investigated. The TEP measured on the pure s-SWCNT film (≈88 μV/K) was found to be almost 7 times higher than that of the m-SWCNTs (≈13 μV/K). Moreover, a quasilinear increase of TEP of the mixed SWCNT networks was observed as the fraction of s-SWCNTs is increased. The experimentally determine

after the surface doping process, which is 10 times higher than that of the pristine device. Subthreshold swing and contact resistance were also improved after the TEOA doping process. The enhancement of the subthreshold swing was demonstrated by using an independent FET model. Furthermore, we found that the doping level can be effectively controlled by the heat treatment method. These results demonstrate a promising material system that is easily controlled with high performance, while elucidat

Surface charge transfer doping (SCTD) has been regarded as an effective approach to tailor the electrical characteristics of atomically thin transition metal dichalcogenides (TMDs) in a nondestructive manner due to their two-dimensional nature. However, the difficulty of achieving rationally controlled SCTD on TMDs <i>via</i> conventional doping methods, such as solution immersion and dopant vaporization, has impeded the realization of practical optoelectronic and electronic devices. Here, we de

Abstract Charge carrier transport in multilayer van der Waals (vdW) materials, which comprise multiple conducting layers, is well described using Thomas–Fermi charge screening (λ TF ) and interlayer resistance ( R int ). When both effects occur in carrier transport, a channel centroid migrates along the c ‐axis according to a vertical electrostatic force, causing redistribution of the conduction centroid in a multilayer system, unlike a conventional bulk material. Thus far, numerous unique prope

-doping on the performance and thermal stability of the QLEDs. We believe that QLEDs with the p-doped HTL can be used for further QLED researches to simultaneously improve the efficiency, lifetime, and high temperature stability, which are highly required for their use in automotive and outdoor displays.

Thickness-dependent bandgap and carrier mobility of two-dimensional (2D) van der Waals (vdW) layered materials make them a promising material as a phototransistor that detects light signals and converts them to electrical signals. Thus far, to achieve a high photoresponsivity of 2D materials, enormous efforts have been made via material and dielectric engineering, as well as modifying device structure. Nevertheless, understanding the effect of interplay between the thickness and the carrier mobi

A system of simple coordinate markers has been developed to facilitate the identification of individual synthetic nanofibers adsorbed on a substrate. The markers are deposited by electron beam lithography and allow to locate any spot on an atomic force microscope image and to deposit new structures close to this spot, such as lithographic contacts to nanotubes. As a demonstration, current–voltage characteristics of a junction between a metallic carbon nanotube and an n-type V2O5 nanofiber were r

When thickness-dependent carrier mobility is coupled with Thomas-Fermi screening and interlayer resistance effects in two-dimensional (2D) multilayer materials, a conducting channel migrates from the bottom surface to the top surface under electrostatic bias conditions. However, various factors including (i) insufficient carrier density, (ii) atomically thin material thickness, and (iii) numerous oxide traps/defects considerably limit our deep understanding of the carrier transport mechanism in

Abstract The interlayer tunneling resistivity ( R int ) and Thomas-Fermi charge screening effects play critical roles in the carrier transport of two-dimensional (2D) multilayer devices. For example, the vertical electric field modifies the R int , resulting in a channel migration along the c -axis. However, because R int varies considerably with the drain electric field in addition to the vertical field, the effective contribution of each layer to the total current varies with the drain bias (

The negative and positive aging effects of quantum dot (QD) light-emitting diodes (QLEDs) have received considerable attention in recent years and various analysis methods have been discussed. Here, we introduce a new approach to understand the aging effect of QLEDs, which is to diagnose the behavior of carriers and traps at interfaces between each layer of the QLEDs and inside the layers themselves. In particular, low-frequency noise (LFN) measurement and the analysis of current in the QLEDs we