Jinok Kim

A High-Performance WSe2 /h-BN Photodetector using a Triphenylphosphine (PPh3 )-Based n-Doping Technique.

The effects of triphenylphosphine (PPh3 )-based n-doping and hexagonal boron nitride (h-BN) insertion on a tungsten diselenide (WSe2 ) photodetector are systematically studied, and a very high performance WSe2 /h-BN heterostucture-based photodetector is demonstrated with a record photoresponsivity (1.27 × 10(6) A W(-1) ) and temporal photoresponse (rise time: 2.8 ms, decay time: 20.8 ms) under 520 nm wavelength and 5 pW power laser illumination.

Effect of O2(CO2)/C4F8O gas combinations on global warming gas emission in silicon nitride PECVD plasma cleaning

Abstract In this study, O2/C4F8O and CO2/C4F8O have been used as the chemicals for plasma-enhanced chemical vapor deposition (PECVD) chamber-cleaning of silicon nitride, and the effects of gas mixture and operational pressure on the silicon-nitride cleaning rate and emission properties, such as emission species, destruction and removal efficiencies (DREs), and million metric tons of carbon equivalent (MMTCE), have been investigated. O2/C4F8O generally showed a higher silicon-nitride cleaning rate compared to CO2/C4F8O, possibly due to the removal of fluorine by carbon in CO2. The highest silicon-nitride cleaning rate obtained with O2/C4F8O was approximately 600 nm/min for 80% O2/20% C4F8O at 66.7 Pa (500 mtorr), 40 sccm, 150 W of 13.56-MHz RF power, and without substrate heating. Emission species, such as CF4, COF2 and CO2, were observed through the exhaust line during silicon nitride cleaning, in addition to the undestructed remaining feed gases. The quantities of these emission species were higher than that of C4F8O fed through the cleaning chamber. With 80% O2/20% C4F8O, the highest DREs and the lowest MMTCE obtained were 92% and 3×10−10, respectively. In the case of CO2/C4F8O, silicon nitride cleaning rates were lower, the DRE was lower and MMTCEs were higher than those of O2/C4F8O.

M-DNA/Transition Metal Dichalcogenide Hybrid Structure-based Bio-FET sensor with Ultra-high Sensitivity

Here, we report a high performance biosensor based on (i) a Cu2+-DNA/MoS2 hybrid structure and (ii) a field effect transistor, which we refer to as a bio-FET, presenting a high sensitivity of 1.7 × 103 A/A. This high sensitivity was achieved by using a DNA nanostructure with copper ions (Cu2+) that induced a positive polarity in the DNA (receptor). This strategy improved the detecting ability for doxorubicin-like molecules (target) that have a negative polarity. Very short distance between the biomolecules and the sensor surface was obtained without using a dielectric layer, contributing to the high sensitivity. We first investigated the effect of doxorubicin on DNA/MoS2 and Cu2+-DNA/MoS2 nanostructures using Raman spectroscopy and Kelvin force probe microscopy. Then, we analyzed the sensing mechanism and performance in DNA/MoS2- and Cu2+-DNA/MoS2-based bio-FETs by electrical measurements (ID-VG at various VD) for various concentrations of doxorubicin. Finally, successful operation of the Cu2+-DNA/MoS2 bio-FET was demonstrated for six cycles (each cycle consisted of four steps: 2 preparation steps, a sensing step, and an erasing step) with different doxorubicin concentrations. The bio-FET showed excellent reusability, which has not been achieved previously in 2D biosensors.

Spatial Control of Photoacid Diffusion in Chemically Amplified Resist (CAR) via External Electric Field

We investigated the effect of an electric field-based post exposure bake (EF-PEB) process on photoacid diffusion and pattern formation. To investigate the control of photoacid diffusion experimentally, the EF-PEB processes was performed at various temperatures. Cross sectional images of various EF-PEB processed samples were obtained by scanning electron microscopy (SEM) after ion beam milling. In addition, we conducted a numerical analysis of photoacid distribution and diffusion with following Ficks second law and compared the experimental results with our theoretical model. The drift distance was theoretically predicted by multiplying drift velocity and EF-PEB time, and the experimental values were obtained by finding the difference in pattern depths of PEB/EFPEB samples. Finally, an EF-PEB temperature of 85 °C was confirmed as the optimum condition to maximize photoacid drift distance using the electric field.