• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.4
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• pp.315-320
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• 2013

The composites composed of conducting polymer (MEH-PPV), CdTe nanoparticles, and multiwalled carbon nanotubes (MWNTs) were spectroscopically and electrically characterized in their thin films. The composite films were prepared by spray coating. These composites were prepared from the mixture solution of MEH-PPV and CdTe-embedded MWNTs, in which CdTe nanoparticles were electrostatically bound to MWNTs. UV/vis and PL spectra were analyzed to investigate the optical absorbance and emission of the composite films. In addition, their structural, electrochemical, and electrical properties were studied by transmission electron microscopy, cyclic voltammetry, and I-V measurement.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.136-141
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• 2007

This paper introduces an artificial neuron which is a nano composite continuous sensor. The continuous nano sensor is fabricated as a thin and narrow polymer film sensor that is made of carbon nanotubes composites with a PMMA or a silicone matrix. The sensor can be embedded onto a structure like a neuron in a human body and it can detect deteriorations of the structure. The electrochemical impedance and dynamic strain response of the neuron change due to deterioration of the structure where the sensor is located. A network of the long nano sensor can form a structural neural system to provide large area coverage and an assurance of the operational health of a structure without the need for actuators and complex wave propagation analyses that are used with other methods. The artificial neuron is expected to effectively detect damage in large complex structures including composite helicopter blades and composite aircraft and vehicles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.45-45
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• 2008

In recent years, new materials and technology has been developed using single-walled carbon nanotubes (SWCNTs) as an alternative to indium tin oxide (ITO) to fulfil the requirements towards novel technological drive. These technologies offer products having a broad range of conductivity, excellent transparency, neutral color tone, good adhesion, abrasion resistance as well as mechanical robustness. In addition, SWCNTs can be solution processed to replace the sophisticated vacuum techniques at high temperatures. In the present work, transparent conducting films were fabricated from the purified SWCNTs. Dispersion of purified SWCNTs was accomplished in 1,2-dichlorobenzene without using surfactants or polymers following ultrasonic process. We achieved coating of nanotubes film on poly ether suiphone (PES) for an average sheet resistance ~110 ${\Omega}/{\Box}$ of optical transmittance 80% at 550 nm. Conventional spin coating method was followed to fabricate films from the purified and dispersed nanotubes solution. The results will be presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.367-372
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• 2002

The vertically well-aligned carbon nanotubes(CNTs) were successfully grown on Ni coated silicon wafer substrate by DC bias-assisted PECVD(Plasma Enhanced Chemical Vapor Deposition). As a catalyst, Ni thin film of thickness ranging from 15~30nm was prepared by electron beam evaporator method. In order to find the optimum growth condition, the type of gas mixture such as $C_2H_2-NH_3$ was systematically investigated by adjusting the gas mixing ratio at $570^{\circ}C$ under 0.4Torr. The diameter of the grown CNTs was 40~200nm and the diameter of the CNTs increased with increasing the Ni particles size. TEM images clearly showed carbon nanotubes to be multiwalled. The measured turn-on field was $3.9V/\mu\textrm{m}$ and an emission current of $1.4{\times}10^4A/\textrm{cm}^2$ was $7V/\mu\textrm{m}$. The CNTs grown by bias-assisted PECVD was able to demonstrate high quality in terms of vertical alignment, crystallization of graphite and the processing technique at low temperature of $570^{\circ}C$ and this can be applied for the emitter tip of FEDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.521-526
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• 2018

In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study, we fabricated a $NO_X$ gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a $450^{\circ}C$ temperature process to increase its detection sensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor, and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gas sensors were used to detect $NO_X$ gas at different concentrations. The gas sensor absorbed $NO_X$ gas molecules, exhibiting increased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained its sensitivity for detecting $NO_X$ gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting $NO_X$ gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect by electronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.418-423
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• 2009

MWCNT(multi-wall carbon nanotube)-doped PEDOT:PSS(poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)), used as a HIL(hole injection layer) material in OLEDs(organic light emitting diodes), was spin-coated on to the ITO glass to form PEDOT:PSS-MWCNT nano composite thin film. Morphology and transparency characteristics of nano composite thin films with respect to the loading percent of MWCNT have been investigated using FT-IR, UV-Vis and SEM. Furthermore, ITO/PEDOT:PSS-MWCNT/NPD/$Alq_3$/Al devices were fabricated, and then J-V and L-V characteristics were investigated. Functional group-incorporated MWCNT was prepared by acid treatment and showed good dispersion property in PEDOT:PSS solution. PEDOT:PSS-MWCNT thin films possessed good transparency property. For multi-layered devices, it was shown that as the loading percent of MWCNT increased, the current density increased but the luminance dramatically decreased. It might be conclusively suggested that the enhanced charge mobility by MWCNT could increase the current density but the hole trapping property of MWCNT could dramatically decrease the hole mobility in the current devices.

• Korean Journal of Optics and Photonics
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• v.21 no.1
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• pp.33-37
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• 2010

We performed time-domain terahertz (THz) spectroscopy to determine optical constants of highly conductive carbon nanotube (CNT) films. The CNT films have been fabricated on a flexible plastic substrate by using spin-coating or vacuum filtration. We found that the transmission of THz waves can be controlled by manipulating the thickness of the films and by post-treatments. From amplitude and phase information of the transmitted THz waves, we obtain optical constants such as refractive indices and dielectric constants of the CNT films. The frequency dependent dielectric constants show good metallic behaviors, relevant to the Drude free electron models with high plasma frequencies. It is also found that the dielectric constants are higher for the acid-treated films. Finally, the frequency dependent dielectric constants which are free from substrate effects have been demonstrated by using CNT films deposited on cellulose membranes.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.113-119
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• 2022

In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.227-233
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• 2005

Carbon nanotubes (CNT) which were grown, on the alumina substrate with a pair of comb-type Au electrodes, by plasma enhanced chemical vapor deposition have been investigated for $NO_2$ gas sensor. The electrical resistance of CNT film decreased with temperature, indicating a semiconductor type of CNT, and also the resistance of CNT sensor decreased with increasing $NO_2$ concentration. Upon exposure to $NO_2$ gas, the electrical resistance of CNT film sensor rapidly decreased within 3 minutes, and then showed a constant value after $20\~30$ minutes. It is found that the sensitivity of CNT sensor has been improved by air oxidation. The CNT sensor oxidized at $450^{\circ}C$ for 30 minutes showed higher sensitivity value than that without oxidation by $27\%$, even for a low 250 ppb $NO_2$ concentration at operating temperature of $200^{\circ}C$. But it needs a recovery time more than 20 minutes for reuse after detection of $NO_2$ gas.

• Composites Research
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• v.26 no.4
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• pp.254-258
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• 2013

Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of $750m^2/g$ showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.