임성일 교수

We report on the fabrication of top-gate phototransistors based on a few-layered MoS(2) nanosheet with a transparent gate electrode. Our devices with triple MoS(2) layers exhibited excellent photodetection capabilities for red light, while those with single- and double-layers turned out to be quite useful for green light detection. The varied functionalities are attributed to energy gap modulation by the number of MoS(2) layers. The photoelectric probing on working transistors with the nanosheet

Mo-based van der Waals heterojunction p-n diodes with p-type α-MoTe2 and n-type MoS2 are fabricated on glass, and demonstrate excellent static and dynamic device performances at a low voltage of 5 V, with an ON/OFF current ratio higher than 10(3) , ideality factors of 1.06, dynamic rectification at a high frequency of 1 kHz, high photoresponsivity of 322 mA W(-1) , and an external quantum efficiency of 85% under blue-light illumination.

Top-gate ferroelectric memory transistors with single- to triple-layered MoS2 nanosheets adopting poly(vinylidenefluoride-trifluoroethylene) [P(VDF-TrFE)] are demonstrated. The nonvolatile memory transistor with a single-layer MoS2 channel exhibits excellent retention properties for more than 1000 s, maintaining ~5 × 103 for the program/erase ratio and displaying a high mobility of ~220 cm2/(V·s). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such

Two-dimensional van der Waals (2D vdWs) materials are a class of new materials that can provide important resources for future electronics and materials sciences due to their unique physical properties. Among 2D vdWs materials, black phosphorus (BP) has exhibited significant potential for use in electronic and optoelectronic applications because of its allotropic properties, high mobility, and direct and narrow band gap. Here, we demonstrate a few-layered BP-based nonvolatile memory transistor w

Black phosphorus (BP) nanosheet is two-dimensional (2D) semiconductor with distinct band gap and attracting recent attention from researches because it has some similarity to gapless 2D semiconductor graphene in the following two aspects: single element (P) for its composition and quite high mobilities depending on its fabrication conditions. Apart from several electronic applications reported with BP nanosheet, here we report for the first time BP nanosheet-ZnO nanowire 2D-1D heterojunction app

Two-dimensional (2D) semiconductor materials with discrete bandgap become important because of their interesting physical properties and potentials toward future nanoscale electronics. Many 2D-based field effect transistors (FETs) have thus been reported. Several attempts to fabricate 2D complementary (CMOS) logic inverters have been made too. However, those CMOS devices seldom showed the most important advantage of typical CMOS: low power consumption. Here, we adopted p-WSe2 and n-MoS2 nanoshee

A van der Waals (vdW) Schottky junction between two-dimensional (2D) transition metal dichalcogenides (TMDs) is introduced here for both vertical and in-plane current devices: Schottky diodes and metal semiconductor field-effect transistors (MESFETs). The Schottky barrier between conducting NbS₂ and semiconducting n-MoS₂ appeared to be as large as ∼0.5 eV due to their work-function difference. While the Schottky diode shows an ideality factor of 1.8-4.0 with an on-to-off cu

Molybdenum disulfide (MoS2) nanosheet, one of two-dimensional (2D) semiconductors, has recently been regarded as a promising material to break through the limit of present semiconductors. With an apparent energy band gap, it certainly provides a high carrier mobility, superior subthreshold swing, and ON/OFF ratio in field-effect transistors (FETs). However, its potential in carrier mobility has still been depreciated since the field-effect mobilities have only been measured from metal-insulator-

Polarization-sensitive photodetection has attracted considerable attention as an emerging technology for future optoelectronic applications such as three-dimensional (3D) imaging, quantum optics, and encryption. However, traditional photodetectors based on Si or III-V InGaAs semiconductors cannot directly detect polarized light without additional optical components. Herein, we demonstrate a self-powered linear-polarization-sensitive near-infrared (NIR) photodetector using a two-dimensional WSe<s

Direct quantitative mapping of the density-of-states, named the photo-excited charge-collection technique, for the interface traps at the n-ZnO and/or p-pentacene thin-film transistor channel is implemented by using monochromatic photons which are carried by optical fibers and are probed onto thin-film transistors.

Abstract Two-dimensional (2D) transition metal dichalcogenides (TMDs)-based van der Waals (vdW) PN junctions have been used for heterojunction diodes, which basically utilize out-of-plane current across the junction interface. In fact, the same vdW PN junction structure can be utilized for another important device application, junction field effect transistors (JFETs), where in-plane current is possible along with 2D–2D heterojunction interface. Moreover, the 2D TMD-based JFET can use both p- an

We have fabricated dual gate field effect transistors (FETs) with 12 nm-thin black phosphorus (BP) channel on glass substrate, where our BP FETs have a patterned-gate architecture with 30 nm-thick Al2O3 dielectrics on top and bottom of a BP channel. Top gate dielectric has simultaneously been used as device encapsulation layer, controlling the threshold voltage of FETs as well when FETs mainly operate under bottom gate bias. Bottom, top, and dual gate-controlling mobilities were estimated to be

We report on the nanosheet-thickness effects on the performance of top-gate MoS(2) field-effect transistors (FETs), which is directly related to the MoS(2) dielectric constant. Our top-gate nanosheet FETs with 40 nm thin Al(2)O(3) displayed at least an order of magnitude higher mobility than those of bottom-gate nanosheet FETs with 285 nm thick SiO(2), benefiting from the dielectric screening by high-k Al(2)O(3). Among the top-gate devices, the single-layered FET demonstrated the highest mobilit