Sukhyung Park

Sidewall mobility and series resistance in a multichannel tri-gate MOSFET

The sidewall mobility and the series resistance in a multichannel tri-gate MOSFET were examined with low-temperature measurement and 2D numerical simulation. With sidewall mobility separated from total transfer characteristics, it was shown that the sidewall conduction is mainly affected by the surface roughness scattering. The effect of surface roughness scattering on sidewall mobility was evaluated with the mobility degradation factor normalized by the low field mobility, which exhibited an almost six times higher value than that of top surface mobility. The series resistance of the multichannel tri-gate MOSFET was studied by comparing with that of the planar MOSFET. Through 2D numerical simulation, it was revealed that relatively high series resistance of the multichannel tri-gate MOSFET is attributed to the variation of doping concentration in the source/drain extension region in the device.

Enhanced voltage-current characteristics of GaN nanowires treated by a selective reactive ion etching

In characterizing the electrical properties of individual NWs (nanowires), the amorphous oxide layer on the surface of NWs is known to limit the electrical conductivity owing to the contact barriers between metal electrodes and NWs. To remove the native oxide layer, a systematic reactive ion etching (RIE) was performed, resulting in a gradual decrease of the diameters of NWs. Voltage-current characteristics of the GaN NW devices treated by tuning the RIE process were improved as reflected by a 1000 times increase in conductance, which was in turn attributed to the removal of the thick (d∼3.5nm) contact barrier formed by the native oxide layer.

The Effects of Mn-doping and Electrode Material on the Resistive Switching Characteristics of ZnO x S 1-x Thin Films on Plastic

Copyright 2014 KIEEME. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The Effects of Mn-doping and Electrode Material on the Resistive Switching Characteristics of ZnOxS1-x Thin Films on Plastic

Electrical characteristics of flexible ZnO thin-film transistors annealed by microwave irradiation

This study examines the effect of microwave annealing upon the electrical characteristics of a representative ZnO thin-film transistor (TFT) deposited on a flexible plastic substrate. After microwave irradiation, the mobility of the TFT is increased from 0.2 to 1.5 cm2/(V s) and its on/off ratio increases from 36.5 to 6.9 × 106. The photoluminescence study reveals that the concentration of oxygen vacancies increases remarkably when the ZnO thin films are exposed to microwave radiation. In this paper, in addition to the results mentioned above, the correlation between the photoluminescence and electrical characteristics is discussed and the electrical characteristics of the ZnO TFT under strain are analyzed.

Electrical and mechanical characteristics of fully transparent IZO thin-film transistors on stress-relieving bendable substrates

In this study, we report the electrical and mechanical characteristics of fully transparent indium zinc oxide (IZO) thin-film transistors (TFTs) fabricated on stress-relieving bendable substrates. An IZO TFT on a stress-relieving substrate can operate normally at a bending radius of 6 mm, while an IZO TFT on a normal plastic substrate fails to operate normally at a bending radius of 15 mm. A plastic island with high Youngs modulus embedded on a soft elastomer layer with low Youngs modulus plays the role of a stress-relieving substrate for the operation of the bent IZO TFT. The stress and strain distributions over the IZO TFT will be analyzed in detail in this paper.

Memory characteristics of flexible resistive switching devices with triangular-shaped silicon nanowire bottom electrodes

In this paper, we demonstrate the bipolar resistive switching characteristics of flexible resistive random access memory (ReRAM) devices, whose bottom electrodes are made of silicon nanowires (Si NWs) with a triangular structure, which offer preferential sites for the filaments. The temperature dependence of the low resistance state (LRS) of the resistive Al2O3/ZnO bilayers of ReRAM devices reveals that Ag filaments originating from the top Ag electrodes are responsible for bipolar resistive switching. With respect to the endurance characteristics of the LRS, resistance fluctuation is negligible because of the filaments generated at the specific sites of the vertices of the Si NW bottom electrodes. In addition, the resistive switching characteristics are maintained even after 1000 bending cycles.

Highly sensitive cholesterol sensors using mixture of cholesterol oxidase and ZnO nanoparticles on plastic

In this study, cholesterol sensors consisting of a mixture of cholesterol oxidase (ChOx) and zinc oxide (ZnO) nanoparticles (NPs) are constructed on plastic substrates and their sensing characteristics are examined in air. The current of the ChOx-ZnO NP film decreases in magnitude as cholesterol molecules are adsorbed on the film, due to the resulting increase in the number of electrons generated by the reaction between the cholesterol and the ChOx. The cholesterol sensor shows a high sensitivity of 1.08 μA/mM and a wide detection range from 10 nM to 1 mM.

Fabrication and Electrical Characteristics of Transparent and Bendable a-IGZO Thin-film Transistors

In this study, we fabricate transparent and bendable a-IGZO (amorphous indium gallium zinc oxide) TFTs (thin-film transistors) with a-IZO (amorphous indium zinc oxide) transparent electrodes on plastic substrates and investigate their electrical characteristics under bending states. Our a-IGZO TFTs show a high transmittance of 82% at a wavelength of 550 nm. And these TFTs have an ratio of , a field effect mobility of , and a subthreshold swing of 186 mV/dec. The good electrical characteristics are retained even after bending with a curvature radius of 18 mm corresponding to a strain of 0.5% owing to mechanical durability of the transparent electrodes used in this study.

A STUDY OF THE RECONSTRUCTION OF ACCIDENTS AND CRIME SCENES THROUGH COMPUTATIONAL EXPERIMENTS

Recently, with an increase in the number of studies of the safety of both pedestrians and passengers, computer software, such as MADYMO, Pam-crash, and LS-dyna, has been providing human models for computer simulation. Although such programs have been applied to make machines beneficial for humans, studies that analyze the reconstruction of accidents or crime scenes are rare. Therefore, through computational experiments, the present study presents reconstructions of two questionable accidents. In the first case, a car fell off the road and the driver was separated from it. The accident investigator was very confused because some circumstantial evidence suggested the possibility that the driver was murdered. In the second case, a woman died in her house and the police suspected foul play with her boyfriend as a suspect. These two cases were reconstructed using the human model in MADYMO software. The first case was eventually confirmed as a traffic accident in which the driver bounced out of the car when the car fell off, and the second case was proved to be suicide rather than homicide.

Atmosphere pressure dependent electrical properties of the ZnO nanowire transistors

Semiconducting nanowire devices were fabricated using photolithography and e-beam lithography, and their electrical properties were studied. Atmosphere pressure dependent electrical properties of the ZnO nanowire field effect transistor (FET) were studied and its analysis methods with PSPICE simulation were applied to explain the conductance changes in nanowire devices. A single ZnO nanowire FET was fabricated by electron beam lithography and its current-voltage characteristics were recorded with varying the atmosphere pressure to test the possible applications as a chemical gas sensor. Current-voltage characteristics showed typical non-ohmic behaviors, reflecting the influence of the contact barriers formed between the ZnO nanowire FET and metal electrodes. In this paper, an equivalent circuit model of the ZnO nanowire FET is suggested in order to model the contact barriers in nanowire devices, showing that most changes of the electrical conductance might originate from the contact region.