김상식 교수

Phototransistors based on multilayer MoS2 crystals are demonstrated with a wider spectral response and higher photoresponsivity than single-layer MoS2 phototransistors. Multilayer MoS2 phototransistors further exhibit high room temperature mobilities (>70 cm2V−1s−1), near-ideal subthreshold swings (∼70 mV decade−1), low operating gate biases (<5 V), and negligible shifts in the threshold voltages during illumination. Detailed facts of importance to specialist readers are published as ”Supporting

Abstract In this study, we fabricate bendable solid-state supercapacitors with Au nanoparticle (NP)-embedded graphene hydrogel (GH) electrodes and investigate the influence of the Au NP embedment on the internal resistance and capacitive performance. Embedding the Au NPs into the GH electrodes results in a decrease of the internal resistance from 35 to 21 Ω, and a threefold reduction of the IR drop at a current density of 5 A/g when compared with GH electrodes without Au NPs. The Au NP-embedded

A route to the top-down fabrication of highly ordered and aligned silicon nanowire (SiNW) arrays with degenerately doped source/drain regions from a bulk Si wafer is presented. In this approach, freestanding n- and p-SiNWs with an inverted triangular cross section are obtained using conventional photolithography, crystal orientation dependent wet etching, size reduction oxidation, and ion implantation doping. Based on these n- and p-SiNWs transferred onto a plastic substrate, simple SiNW-based c

The photoluminescence spectrum of undoped epitaxial wurtzite GaN layers on sapphire was measured for applied hydrostatic pressures up to 73 kbar at 9 K and up to 62 kbar at 300 K. The pressure dependences of the I2 exciton recombination line and the ‘‘yellow’’ band (2.2 eV band at ambient pressure) were examined at 9 and 300 K, and the series of donor-acceptor-pair emission lines was analyzed at 9 K. From the I2 lines, it was found that the band gap increases with pressure by 4.4±0.1 meV/kbar at

In this study, we present the steep switching characteristics of bendable feedback field-effect transistors (FBFETs) consisting of p(+)-i-n(+) Si nanowires (NWs) and dual-top-gate structures. As a result of a positive feedback loop in the intrinsic channel region, our FBFET features the outstanding switching characteristics of an on/off current ratio of approximately 10(6), and point subthreshold swings (SSs) of 18-19 mV/dec in the n-channel operation mode and of 10-23 mV/dec in the p-channel op

Resistance switching memory devices constructed on flexible plastic substrates via the spin-coating of titanium oxide solution were characterized in this study. The resistance switching memory device exhibited a ratio of the high resistance to low resistance states of more than 102, and this large resistance ratio was maintained even after 104 s. These memory characteristics are comparable to those of resistance switching memory devices based on titanium oxide films deposited on Si substrates. M

In this study, we propose newly designed feedback field-effect transistors that utilize the positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, I–V characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec −1 , an on/off current ratio of approximately 10 11 , and an on-cur

Abstract This paper demonstrates that thermal energy radiated from a human finger can be converted efficiently into electricity by a nanocrystal (NC) thin film that substantially suppresses thermal conduction, but still allows electric conduction. The converting efficiencies of the chalcogenide NC thin films with dimensions 40 µm × 20 µm × 20 nm, prepared on flexible substrates by a solution process, are maximized by adjusting the NC size. A Seebeck coefficient of S = 1829 µV K −1 , and a dimens

Abstract Memory hierarchy among conventional memory technologies is one of the main bottlenecks in modern computer systems; alternative memory technologies are thus necessary for quasi‐nonvolatile memory applications. Herein, a fully complementary metal‐oxide‐semiconductor‐compatible quasi‐nonvolatile memory composed of p + ‐n‐p‐n + silicon on a silicon‐on‐insulator substrate is presented. The quasi‐nonvolatile silicon memory device demonstrates high‐speed write capability ( ≤ 100 ns), long rete

In this study, we propose a simple way to improve thermal stability of solid-state supercapacitors (SCs) by adding carbon black (CB) into reduced graphene oxide (rGO) electrodes. The CB used as a heat-resistant additive contributes to stable operation of the rGO-CB SC even after 1000 charge/discharge cycles at 90 °C. In the case of the rGO SC without CB, it fails after the 166th cycles at 90 °C. Compared with the rGO SC, the rGO-CB SC exhibits the decrease in internal resistance from 42 to 18 Ω

In this study, we demonstrate the abruptly steep-switching characteristics of a feedback field-effect transistor (FBFET) with a channel consisting of a p(+)-i-n(+) Si nanowire (NW) and charge spacers of discrete nanocrystals on a plastic substrate. The NW FBFET shows superior switching characteristics such as an on/off current ratio of ∼10(5) and an average subthreshold swing (SS) of 30.2 mV/dec at room temperature. Moreover, the average SS and threshold voltage values can be adjusted by program

This study demonstrates the fabrication and characterization of a flexible thermoelectric (TE) power generator composed of silicon nanowires (SiNWs) fabricated by top‐down method and discusses its strain‐dependence analysis. The Seebeck coefficients of the p‐ and n‐type SiNWs used to form a pn‐module are 156.4 and −146.1 µV K −1 , respectively. The maximum power factors of the p‐ and n‐type SiNWs are obtained as 8.79 and 8.87 mW (m K 2 ) −1 , respectively, under a convex bending of 1.11%, respec