Seung Youl Kang

Growth and field electron emission of vertically aligned multiwalled carbon nanotubes

Vertically well-aligned carbon nanotubes (CNTs) are grown on a Ni deposited silicon oxide substrate at 950°C by thermal chemical vapor deposition using C2H2. The uniformly grown CNTs with a diameter of about 60 nm have unique beak-like tips without any encapsulated Ni particles inside and exhibit high field emission current density, e.g. 2.9 mA/cm2 at 3.7 V/μm, following a Fowler–Nordheim behavior.

Growth of well-aligned carbon nanotubes on a large area of Co–Ni co-deposited silicon oxide substrate by thermal chemical vapor deposition

Abstract We have grown vertically well-aligned multiwalled carbon nanotubes (CNT) on a large area of cobalt–nickel (Co–Ni) co-deposited silicon oxide substrate by thermal chemical vapor deposition using C 2 H 2 gas, at 950°C. The diameter of CNTs is in the range of 50–120 nm and the length is about 130 μm. The grown CNTs have a bamboo structure and closed tip with no catalytic particles inside. As the particle size of Co–Ni catalyst decreases, the vertical alignment is enhanced. The CNTs exhibits a low turn-on voltage of 0.8 V/μm with an emission current density of 0.1 μA cm −2 .

The vertically stacked organic sensor-transistor on a flexible substrate

The authors report on the photo-response characteristics of flexible sensor-transistor circuits (ST-circuits) made with (poly(3-hexylethiophene)/phenyl-C61-butryic acid methyl ester) (P3HT/PCBM) bulk heterojunction polymer and pentacene-based organic field-effect transistors, which are stacked via poly(dimethylsiloxane) (PDMS) on the plastic substrate. The results indicate that the anode-source current is variable because of both the charge separation of the photogenerated excitons and the accumulated charges at the OFET channel layer. The light dependent photo response (ΔI/I0) is modulated from 0.47 to 1.9 by the gate-source voltage at the fixed anode-source voltage of the ST-circuits.

Low Temperature Aluminum Oxide Gate Dielectric on Plastic Film for Flexible Device Application

The growth of low temperature aluminum oxide gate dielectric on a plastic substrate is explored for flexible device application. Single-crystal-transferred-silicon is used as a channel layer. A plasma-deposited interfacial oxide layer is found beneficial for better device performances. Additional forming gas annealing also improved contact resistance and resulted in better passivation of defect sites, hence, enhanced performances. High mobility, high on current with large on–off ratio and low threshold voltage was achieved. The flexibility of the device is also reported. Devices show nearly no changes in electrical properties after bending the device to a strain value of up to 0.3%, corresponding to a bending radius of 4 mm.

Carbon nanotube and conducting polymer dual-layered films fabricated by microcontact printing

We report carbon nanotube/conducting polymer dual-layered film (CPDF) electrodes fabricated by microcontact printing for flexible transparent electrodes of organic thin film transistors (OTFTs). The CPDFs show ∼1000 Ω/sq surface resistivity and ∼93% transmittance at an extremely low loading of single-walled carbon nanotubes, and can be self-aligned with a precision of 20 μm. The CPDFs are applied as the source and drain electrodes in OTFTs without any supplementary alignment process, which leads to a mobility and a current on/off ratio of approximately 0.02 cm2 V−1 s−1 and ∼104, respectively.

PROPERTIES OF FERROELECTRIC P(VDF-TrFE) 70/30 COPOLYMER FILMS AS A GATE DIELECTRIC

ABSTRACT We directly formed the organic ferroelectric P(VDF-TrFE) 70/30 copolymer film by the spin coating for making the MFS structure in the silicon wafer. To understand the crystallization behavior of P(VDF-TrFE) 70/30 copolymer, the morphologies of copolymer thin films were studied by AFM and XRD. AFM studies revealed that as grown and annealed films showed surface roughness greater than amorphous films due to crystallization. The XRD spectrum of the films subjected to various annealing temperatures showed β -phase and this phase content was maximum at 140°C annealing. The capacitance shows hysteresis behavior like a buttery shape due to the polarization reversal in the film and this result indicates clearly that the film has a ferroelectric property. The dielectric constants of the P(VF2-TrFE) copolymer films calculated from the capacitance at the two peak points of the C-V characteristics were about 8.7.

Etching Characteristics of Ba ( Mg1 / 3Ta2 / 3 ) O 3 Film by Using Cl2 / SF 6 Electron Cyclotron Resonance Plasma

We investigated the etch characteristics of Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) films using Cl 2 /SF 6 gas mixtures with electron cyclotron resonance plasma. The etch rate in pure Cl 2 gas plasma was approximately 1250 A/min and was decreased by the addition of SF 6 . By quadrupole mass spectrometer analysis, we found that the etch rate had a close relationship to the Cl radical. The surface reaction on the BMT films during the etch was examined by X-ray photoelectron spectroscopy analysis. It is proposed that the BaCl x O y compound has been formed by Cl 2 gas plasma. The chemical surface reaction and BMT etch characteristics with SF 6 /Cl 2 gas chemistries are discussed in detail.

Hydrogen Defect Passivation of Silicon Transistor on Plastic for High Performance Flexible Device Application

The electrical characteristics of a transistor on a transferred silicon ribbon are demonstrated. The process temperature is limited to 200°C for potential use on plastic sheets. Additional hydrogen annealing reduces the threshold voltage and improves the transistor properties. A high mobility of around 160 cm 2 /V s, with a high on/off ratio and an off current of as low as < 10 11 A, is achieved. The flexibility of the device is evaluated after applying stress in the bended condition. The device shows very little change in properties with a bending radius <4 mm. Overall, good electrical and mechanical properties are demonstrated for future use on flexible device applications.

Microencapsulation of Polymer Coated Color Pigments for Multi-Color Electrophoretic Display

In this study, we have investigated microencapsulation of magenta, yellow, and cyan color polymer balls with white pigment for multi-color electrophoretic display implementation. The charged color pigments have been prepared by physical coating of magenta, yellow, and cyan with functionalized polymers, then surface charging with charge control agent. These color balls with white pigment were microencapsulated in suspending fluid through in-situ polymerization.

Characterization and removal of trace heavy metal contamination on Si-surface resulted from CHF3/C2F6 reactive ion etching

The characteristics of removal of trace heavy metal contamination on the silicon surface resulted from CHF3/ C2F6 reactive ion etching (RIE) was studied using total reflection X-ray fluorescence spectroscopy (TRXRF). In order to investigate the depth profile of metallic contaminants near the surface, TRXRF measurements containing glancing angle scans were performed after slightly etching of silicon surface by repeating the cleaning procedures that diluted HF (DHF) removed the oxide grown by the mixture of H2SO4 and H2O2 (SPM) or O2 plasma ashing treatment. RIE and O2 plasma ashing processes resulted in metal contamination such as Fe, Ni, Zn, etc. They were present as both of plate-type and bulk-type, and the large part of plate-type contamination was removed easily. Especially, Fe resulted from RIE was the most abundant contaminant and its concentration was ~1011 atoms/ cm2. Fe was mainly distributed within ~2 nm from silicon surface and could be effectively reduced below ~2×1010 atoms/ cm2 by etching of ~2.5 nm depth of the silicon substrate.