• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.338-342
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• 2010

Carbon nanotubes (CNTs) have excellent electrical, chemical stability, mechanical and thermal properties. The MWCNT films were investigated as a transparent electrode for the solar cell, OLED, and field-emission display. MWCNT films were fabricated by air spray method, whose process is quite low-costed, using the multi-walled CNTs solution on glass substrates. Moreover, the most stable film was fabricated when the spraying time was 60 sec. The film that was sprayed with the MWCNT dispersion for 60 sec, has 300nm thick. And its electric resistivity, transmittance rate, mobility and carrier concentration are $6{\times}10^{-2}{\Omega}{\cdot}cm$, 50% at ${\lambda}=550mm$, $4.3{\times}10^{-2}cm^2/V{\cdot}s$ and $2.1{\times}10^{21}cm^{-3}$, respectively. Also, absorption energy of MWCNT films show from 3.9 eV to 4.6 eV. Furthermore, we can use MWCNT films fabricated by the spray method for the transparent electrode.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.67-74
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• 1998

Two kinds of polished and unpolished freestanding films prepared by DC plasma CVD method were impacted by SiC particles to understand erosion mechanism. Erosion damage caused by solid impact was characterized by surface profilometer, scanning electron microscopy and Raman spectroscopy. Gradually decrease of surface roughness and sharp reduction of crystallinity for unpolished CVD films were observed with increasing erosion time. It was found that smaller grains of the diamond were removed in early stage of erosion process and larger grains were eroded with further impingement. By introduction of re-growth method on polished diamond, further understanding of erosion mechanism was achieved. Most of the surface fractures were initiated at the grain boundary.

• Carbon letters
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• v.13 no.4
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• pp.248-253
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• 2012

Dielectrophoretic filtering and alignment of single-walled carbon nanotubes (SWCNTs) were tested using deuterium oxide as a solvent. A solution of deuterium oxide-SWCNTs was dropped on top of a silicon chip and an ac electric field was applied between pre-defined electrodes. Deuterium oxide was found to be a better solvent than hydrogen oxide for the dielectrophoresis process with higher efficiency of filtering. This was demonstrated by comparing Raman spectra measured on the initial solution with those measured on the filtered solution. We found that the aligned nanotubes along the electric field were not deposited on the substrate but suspended in solution, forming chain-like structures along the field lines. This so-called pearl chain formation of CNTs was verified by electrical measurements through the aligned tubes. The solution was frozen in liquid nitrogen prior to the electrical measurements to maintain the chain formation. The current-voltage characteristics for the sample demonstrate the existence of conduction channels in the solution, which are associated with the SWCNT chain structures.

• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.226-232
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• 1990

The degradation phenomena and thermal stability of 2.5Y-TZP at low-temperature were studied by means of XRD, Raman spectra and microstructural analysis. The degradation of heat-treated 2.5Y-TZP at 20$0^{\circ}C$-20hr in air was observed on the TZP surface, be caused by the cracks generated from tlongrightarrowm transformation, and the cracks was propagated inside the polycrystalline body. The ZrO2 grain boundaries and grains near the crack were revealed as if these were diffused and dissolved. And it was also observed mlongrightarrowt transformation as the degraded TZP was refired at 140$0^{\circ}C$, and it was thought to be the fact that the moisture in atmosphere during the aging process contributed to the degradation. The thermal stability of 2.5Y-TZP was improved dramatically with an addition of 3w/o CeO2 or a provision of high Y2O3 concentration on the TZP surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.188.2-188.2
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• 2014

Chemical vapor deposition (CVD) method is usually used to grow high-quality large area graphene. In the CVD process, copper is an especially important catalytic-substrate due to the fact that graphene films grown on Cu foils are predominantly one monolayer thick. In this study, we has grown graphene on several types of copper substrates: Cu foils and copper single crystal surfaces such as Cu(100) and Cu(111) are chosen. To investigate the differences between graphene grown on foils and single crystals, we use Raman spectroscopy, X-ray diffraction and atomic force microscopy. Details of the experimental results will be presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.574-574
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• 2012

We report a simple way of fabricating high-quality carbon nanoscrolls (CNSs) by taking advantage of strain relief due to large difference in strain at the interface of graphene and underlying layer. This method allows strain-controlled self rolling-up of monolayer graphene during etching process at predefined positions on SiO2/Si substrates by photolithography. The size and the length of the CNSs can be easily controlled by adjusting the thickness of the underlying layer and by pre-patterning. Raman spectroscopy studies show that the CNSs is free of significant defects, and the electronic structure and phonon dispersion are slightly different from those of two-dimensional graphene. The preparation of high-quality CNSs may open up new opportunities for both fundamental and applied research of CNSs.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.529-529
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• 2012

Dispersion of carbon nanotubes in biocompatible media are of particular interest for diverse biomedical and nanomedicine applications. Various biomolecules and biopolymers such as DNA, proteins, poly L-lysine, starch, gelatin, steroid biosurfactants, and chitosan have shown capability for the effective dispersion of carbon nanotubes in water. Chitosan has demonstrated capacity for effective dispersion of single-walled carbon nanotubes (SWCNTs) in acidic medium and it also showed tendency to preferentially disperse smaller diameter nanotubes. Chemical functionalizations of chitosan enable its solubility in neutral pH water by reducing the intra and inter molecular hydrogen bonding. Herein, we present a neutral pH water soluble chitosan derivative, chitosan-hydroxyphenyl acetamide (CHPA), obtained by functionalizing the amino groups of chitosan with 4-hydroxyphenyl acetic acid, as an efficient biocompatible dispersant for debundling and solubilization of SWNTs in neutral aqueous solutions. Various process conditions for individual dispersion of SWCNTs are analyzed based on optical absorption and Raman spectroscopy.

• Journal of Sensor Science and Technology
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• v.21 no.5
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• pp.385-388
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• 2012

This paper describes the synthesis and characterization of graphene by RTA process. Amorphous 3C-SiC were deposited using APCVD for carbon source and Ni layer were employed for transition layer. Various parameters of the ramping speed, the annealing time and the cooling speed are evaluated for the optimized combination allowed for the reproducible fabrication of graphene using 3C-SiC thin film. For analysis of crystalline Raman spectra was employed. Transferred graphene shows a high IG/ID ratio of 2.73. SEM and TEM images show the optical transparency and 6 carbon network, respectively. Au electrode deposited on the transferred graphene shows linear I-V curve and its resistance is 358 ${\Omega}$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.293-293
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• 2014

The applicability of graphene has been demonstrated in the electronic fields. But, high performance of graphene is limited by the contact resistance (Rc) at the metal-graphene interface. Recently, Rc was found to be improved by forming edge-contacted graphene via theoretical simulation. Based on the differences between the surface and edge contacts at the M-G interface, we demonstrate "edge-contacted" graphene through the use of a controlled plasma processing technique that generates the edge structure of the bond and significantly reduces the contact resistance. The contact resistance attained by using pre-plasma processing was of $270{\Omega}{\cdot}{\mu}m$. Mechanisms of pre-plasma process leading to low Rc was revealed by SEM and Raman spectroscopy. In the end, controlled pre-plasma processing enabled to fabricate CVD-graphene field effect transistors with an enhanced adhesion and improved carrier mobility.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.12
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• pp.558-560
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• 2005

The carbon film was deposited by the electrolysis of methanol solution. Carbon films have been grown on silicon substrates using the method of chemical process. From investigations of the Raman spectroscopy and the FTIR spectroscopy, the carbon film deposited by the electrolysis was identified the hydrogenated carbon film with the porous structure. The carbon film deposited by elctrolysis of methanol was identified as the hydrogenated carbon film with porous structure. Deposition parameters for the growth of the carbon films were current density, methanol liquid temperature. We electrical resistance and surface morphology of carbon films formed various conditions specified by deposition parameters. It was clarified that the high electrical resistance carbon films with smooth surface morphology are grown when a distance between the electrodes is relatively wider. We found that the electrical resistance in the films independent of both current density and methanol liquid temperature. The temperature dependence of the electrical resistance in the low resistance carbon films is different from one obtained in graphite..