• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.92-95
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• 1997

Because of the novel characteristics such as chemical stability, hardness, electrical resistivity and thermal conductivity, diamond-like carbon (DLC) film is a suitable material for the passivation layers. For this purpose, using the PECVD, DLC films were synthesized at room temperature. The adhesion and the hardness of the DLC films deposited on Si an SiO2 substrate were measured. The resistivity of 5.3$\times$$10^8$$\Omega$.cm was measured by automatic spreading resistance probe analysis method. The thermal conductivities of different DLC films were measured and compared with that of phospho silicate glass (PSG) film which is commonly used as passivation layers. The thermal conductivity of DLC film was improved by increasing hydrogen flow rate up to 90 sccm and was better than that of PSG film. The patterning techniques of the DLC film developed using the RIE and the lift-off method to form 5$\mu\textrm{m}$ line. Finally, the thermal characteristics of the power transistor with the DLC film as passiviation layer was analyzed.

• Particle and aerosol research
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• v.6 no.2
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• pp.61-67
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• 2010

In this paper, we describe a new method to form polymer thin films, in which carbon nanotubes (CNTs) are homogeneously distributed so that they can strengthen the mechanical property of resulting polymer film. To do so, we first homogeneously mixed CNTs with polymer in a DMF solvent. With the assistance of ultrasonic nebulizer, the polymer/CNT solution was then aerosolized into micro-sized droplets and finally turned into solidified polymer/CNT composite particles by gas-phase drying process. As the results of SEM and TEM analysis, CNTs were found to be homogeneously immobilized in the polymer matrix particles due to rapid drying process in the gas phase. For comparison purpose, (i) the polymer/CNTs composite particles prepared by aerosol processing method and (ii) polymer/CNTs sheets prepared by simple solution-evaporation method were employed to form polymer/CNTs composite thin films using a hot press. As the result, the aerosol processing of composite particles was found to be a much more effective method to form homogeneously distributed-CNTs in the polymer matrix thin film.

• 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.

• Tribology and Lubricants
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• v.10 no.3
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• pp.29-38
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• 1994

The friction and wear of mild steel at dry sliding surfaces under different vacuum conditions have been investigated to understand the wear mechanisms. For the test, a ball-ondisk typed wear-rig has been built and implemented, allowing control of sliding speed, load and vacuum. Results show that, at a high sliding velocity, friction of low carbon steel (SS41) under a high vacuum is much higher than that of ambient condition and wear is much severer. It is due to lack of effective oxidation film formation on which steel surfaces could protect themselves against the severe wear. It has been shown, however, that there is a critical regime with contact conditions (at a low sliding velocity, a low load, and under a medium vacuum) at which effective, protective films of low carbon steel have been built on the surfaces in a friction process with a self-regulating way, resulting in both very low coefficients of friction (about 0.3) and mild wear. In order to investigate the protective films on steel surfaces, the worn surfaces and the wear debris have been experimentally analyzed with SEM, AES/SAM and XRD. A theoretical analysis of frictional heating at sliding surfaces, and an experimental analysis of the influence of oxidation wear under various vacuum conditions are described. The important variables on which self-formations of protective films at dry sliding surfaces depend, and the wear mechanisms are also investigated.

• KSTLE International Journal
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• v.3 no.1
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• pp.38-42
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• 2002

Diamond-like Carbon(DLC) films were deposited on Si wafers by an RF-plasma-assisted CVD using CH$_4$gas. Tribological tests were conducted with the use of a rotating type ball on a disk friction tester with dry air. This study made use of four kinds of mating balls that were made with stainless steel but subjected to different annealing conditions in order to achieve different levels of hardness. In all load conditions, testing results demonstrated that the harder the mating materials, the lower the friction coefficient was. The friction coefficients were fecund to be lower with austenite mating balls than with fully annealed martensite balls. Conversely, the high friction coefficient found in soft martensite balls appeared to be caused by the larger contact area between the DLC film and the ball. The wear tracks on DLC films and mating balls could prove that effect. Measuring the wear track of both DLC films and mating balls revealed a similar tendency compared to the results of friction coefficients. The wear rate of austenite balls was also less than that of fully annealed martensite balls. Friction eoefficients decrease when applied leads exceed critical amount. The wear track on mating balls showed that a certain amount of material transfer occurs from the DLC film to the mating ball during a high friction process. Raman Spectra analysis Showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.231-234
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• 2000

Vertically aligned carbon nanotubes were synthesized on Ni-coated Si substrates using microwave plasma-enhanced chemical vapor deposition. The grain size of Ni thin films was varied with the RF power density during the RF magnetron sputtering process. It was found that the diameter, growth rate, and density of carbon nanotubes could be controlled systematically by the grain size of Ni thin films. With decreasing the grain size of Ni thin films, the diameter of the nanotubes decreased, whereas the growth rate and density increased. High-resolution transmission electron microscope images clearly demonstrated synthesized nanotubes to be multiwalled. The number of graphitized wall decreased with decreasing the diameter. Field emission properties will be further presented.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.55-56
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• 2000

We report the fabrication of carbon nanostureture films with excellent electron-emission characteristics on chrome electrodes using a pre-deposited transition metal catalyst layer. The emission current densities of 1 ${\mu}A/cm^2$ and 1 $mA/cm^2$ were measured at the electric field of 2.5 and 4.8 $V/{\mu}m$, respectively, and the current fluctuation of less than 2.5% was observed at the average current density 211 ${\mu}A/cm^2$ for the measurement duration of 20 minutes. We counted more than ${\sim}10^4$ emission sites per $cm^2$ from the emission images, and also noticed good mechanical stability. Moreover, we were able to fabricate good electron-emitting carbon films on chrome electrodes on Corning glass substrates at the nominal temperature below $650^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.326-331
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• 2000

We have fabricated the field emitter arrays coated with diamond-like carbon (DLC) films that improved the field emission characteristics. The nitrogen doped DLC films are prepared by the filtered cathodic vacuum are (FCVA) tehnique. The activation energy of the nitrogen doped DLC films are derived from electrical conductivity measurements. The silicon field emission arrays (FEAs) were prepared by the VLSI technique. The turn-on field was rapidly decreasing and the emission current was remarkably increasing the DLC-coated FEAs than the non-coated silicon FEAs. In the nitrogen doped FEAs, the turn-on field decreased and the emission current increased with increasing the nitrogen found out the field emission current and the work function of the DLC-coated FEAs was remarkably decreased than that of the non-coated silicon FEAs. As nitrogen doping concentrations are increased the work function of FEAs is decreased and the field emission properties are improved in nitrogen doped DLC-coated FEAs. This phenomenon in due the fact that the Fermi energy level moves to the conduction band by increasing nitrogen doping concentration.

• The Korean Journal of Ceramics
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• v.3 no.3
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• pp.182-186
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• 1997

Diamond-like carbon(DLC) films were deposited on silicon substreates by using an RF plasmaassisted CVD apparatus; the effects of deposition conditions such as CH4 gas pressure and substrate bias voltage on DLC film friction and wear were examined in both friction and scratch tests. In friction tests critical loads at which the friction coefficient increases abruptly depend on substrate bias voltages: critical loads deposited at a bias voltage of -100 V exceed those deposited at other bias voltages. Critical loads are correlated with DLC film hydrogen content. Critical DLC film loads in scratch tests depended considerably less than in friction tests. The friction coefficient of DLC films depends on neither substrate bias voltage nor CH4 gas pressure.

• Carbon letters
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• v.13 no.1
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• pp.44-47
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• 2012

We analyzed the effect of etchants for metal catalysts in terms of the characteristics of resulting graphene films, such as sheet resistance, hall mobility, transmittance, and carrier concentration. We found the residue of $FeCl_3$ etchant degraded the sheet resistance and mobility of graphene films. The residue was identified as an iron oxide containing a small amount of Cl through elemental analysis using X-ray photoelectron spectroscopy. To remove this residue, we provide an alternative etching solution by introducing acidic etching solutions and their combinations ($HNO_3$, HCl, $FeCl_3$ + HCl, and $FeCl_3+HNO_3$). The combination of $FeCl_3$ and acidic solutions (HCl and $HNO_3$) resulted in more enhanced electrical properties than pure etchants, which is attributed to the elimination of left over etching residue, and a small amount of amorphous carbon debris after the etching process.