• Journal of Industrial Technology
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• v.39 no.1
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• pp.7-14
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• 2019

Carbon nanotubes (CNT) on metal substrates are definitely beneficial because they can maintain robust mechanical stability and high conductivity between CNT and metal interfaces. Here, we report direct growth of CNT on Ni-based superalloy, Inconel 600, using thermal chemical vapor deposition (CVD) with acetylene feedstock in the growth temperature range of $400-725^{\circ}C$. Furthermore, we studied the effect of substrate pretreatment on the growth yield enhancement and growth temperature decrease of CNT on Inconel 600. Activation energy (AE) for CNT growth was estimated from the CNT height change with respect to the growth temperature. The AE values significantly decreased from 205.03 to 24.35 kJ/mol by the pretreatment of thermal oxidation of Inconel substrate at $725^{\circ}C$ under ambient. Higher oxidation temperature tends to have lower activation energy. The results have shown the importance of pretreatment temperature on CNT growth yield and growth temperature decrease.

• Journal of Hydrogen and New Energy
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• v.21 no.1
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• pp.50-57
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• 2010

Stepwise production of syn-gas and hydrogen from methane on ferrite based media added with yttria-stabilized zirconia (YSZ) was carried out using a fixed bed infrared reactor. In this study, all M-ferrite (M=Co, Cu, Mn and Ni) media were prepared by co-precipitation method, and there the YSZ was added as a binder to improve thermal stability, reactivity, and resistance against carbon deposition. Most of the ferrite media containing YSZ showed the good redox property for temperature programmed reduction/oxidation (TPR/O) tests. Notably, the Cu-substituted ferrite medium with YSZ showed the great resistance against carbon deposition as well as the good reactivity for the stepwise production of syngas and hydrogen. Furthermore, it also showed the good durability without significant deactivation during five repeated cyclic tests.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.78-78
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• 2013

Recently, many platinoid metals like platinum and ruthenium have been used as an electrode of microelectronic devices because of their low resistivity and high work-function. However the material cost of Ru is very expensive and it usually takes long initial nucleation time on SiO2 during chemical deposition. Therefore many researchers have focused on how to enhance the initial growth rate on SiO2 surface. There are two methods to deposit Ru film with atomic layer deposition (ALD); the one is thermal ALD using dilute oxygen gas as a reactant, and the other is plasma enhanced ALD (PEALD) using NH3 plasma as a reactant. Generally, the film roughness of Ru film deposited by PEALD is smoother than that deposited by thermal ALD. However, the plasma is not favorable in the application of high aspect ratio structure. In this study, we used a bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)2] as a metal organic precursor for both thermal and plasma enhanced ALDs. In order to reduce initial nucleation time, we use several methods such as Ar plasma pre-treatment for PEALD and usage of sacrificial RuO2 under layer for thermal ALD. In case of PEALD, some of surface hydroxyls were removed from SiO2 substrate during the Ar plasma treatment. And relatively high surface nitrogen concentration after first NH3 plasma exposure step in ALD process was observed with in-situ Auger electron spectroscopy (AES). This means that surface amine filled the hydroxyl removed sites by the NH3 plasma. Surface amine played a role as a reduction site but not a nucleation site. Therefore, the precursor reduction was enhanced but the adhesion property was degraded. In case of thermal ALD, a Ru film was deposited from Ru precursors on the surface of RuO2 and the RuO2 film was reduced from RuO2/SiO2 interface to Ru during the deposition. The reduction process was controlled by oxygen partial pressure in ambient. Under high oxygen partial pressure, RuO2 was deposited on RuO2/SiO2, and under medium oxygen partial pressure, RuO2 was partially reduced and oxygen concentration in RuO2 film was decreased. Under low oxygen partial pressure, finally RuO2 was disappeared and about 3% of oxygen was remained. Usually rough surface was observed with longer initial nucleation time. However, the Ru deposited with reduction of RuO2 exhibits smooth surface and was deposited quickly because the sacrificial RuO2 has no initial nucleation time on SiO2 and played a role as a buffer layer between Ru and SiO2.

• Korean Journal of Materials Research
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• v.3 no.2
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• pp.103-110
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• 1993

Abstract It has been attempted to make the copper-graphite composites by deposition of copper on the surface of graphite through the hydrogen reduction of copper chlorides. Both KISH and natural graphites of less than 325 mesh were used as substrates and the hydrogen reduction also was conducted in the range of 350-50$0^{\circ}C$. The distribution of copper on the surface of graphite was found to increase with the decrease of reduction temperature. In addition. the partial pressure of hydrogen played an important role in the overall rate of reduction which was substantially dominated by the chemical reaction on the surface of each particle. It was concluded that the reduction temperature should be maintained as low as possible to accomplish the well distribution of copper in the composites.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.124-132
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• 2007

This work investigated a fabrication way of stable platinized Ti electrode and evaluated the electrochemical characteristics of the Sn-modified platinized Ti electrode in nitrate solution. A Pt electro-plating way to form some open special clearances within the Pt coating layer on etched Ti substrate was very important to remove effectively the residual contaminate due to plating solution out of the fabricated electrode surface and to maximize the actual electrode surface area contacting solution. Both boiling and electro-cleaning processes of the fabricated electrode was essential to obtain a stable platinized-Pt electrode with reproducible and stable surface property which was necessary for the correct evaluation of Sn coverage on the electrode. The electro-cleaning caused a morphology change of the platinized Ti electrode surface with some downy hair-like polyps formed during the deposition disappearing, which made the electrode stable. The Sn-modified platinized Ti electrode in this work showed the best electro-activity for nitrate reduction, when it was fabricated through the Pt electro-plating of about 30 minutes.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.67-71
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• 2013

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.

• Carbon letters
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• v.14 no.3
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• pp.171-174
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• 2013

The high quality contact between graphene and the metal electrode is a crucial factor in achieving the high performance of graphene transistors. However, there is not sufficient research about contact resistance reduction methods to improve the junction of metal-graphene. In this paper, we propose a new method to decrease the contact resistance between graphene and metal using directly grown graphene over a metal surface. The study found that the grown graphene over copper, as an intermediate layer between the copper and the transferred graphene, reduces contact resistance, and that the adhesion strength between graphene and metal becomes stronger. The results confirmed the contact resistance of the metal-graphene of the proposed structure is nearly half that of the conventional contact structure.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.1-6
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• 2003

Flow modulation chemical vapor deposition process has been reported as an alternative way to obtain low resistivity, low residual chlorine content and good step-coverage titanium nitride film. Flow and concentration characteristics in a vertical FMCVD reactor are analyzed by using computational fluid dynamics method. The results show that 1.0 second as Cl reduction period is too short and there is still $TiCl_4$ gas above the holder at the end of the period. Time variation of $TiCl_4$ gas concentration on the holder shows that at least 3.0 second is necessary as Cl reduction time for the sake of film characteristics.

• Clean Technology
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• v.24 no.3
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• pp.183-189
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• 2018

Hollow carbon spheres (HCS) and carbon spheres (CS) were prepared by a hydrothermal reaction and they were introduced as a substrate for the deposition of $MnO_2$ nanoparticles. The $MnO_2$ nanoparticles were deposited on the carbon surface by a chemical redox deposition method. After deposition, the $MnO_2$ nanoparticles were uniformally distributed on the carbon surface in a slit-shape, and sparse $MnO_2$ slits appeared on the HCS surface. The $MnO_2-HCS$ showed an initial specific capacitance of $164.1F\;g^{-1}$ at scan rate of $20mv\;s^{-1}$, and after 1,000 cycles, the specific capacitance was maintained to $141.3F\;g^{-1}$. The capacity retention of $MnO_2-HCS$ and $MnO_2-CS$ were calculated to 86% and 78% in the cycle performance test up to 1,000 cycles, respectively. $MnO_2-HCS$ showed a good cycle stability due to the mesoporous hollow structure which can cause a faster diffusion of the electrolyte and can easily adsorb and desorb $Na^+$ ions on the surface of the electrode.

• Korean Journal of Materials Research
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• v.15 no.3
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• pp.149-154
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• 2005

Teflon like fluorocarbon thin films have been deposited on silicon and oxide molds as an antistiction layer for the hot embossing process by an inductively coupled plasma (ICP) chemical vapor deposition (CVD) method. The process was performed at $C_4F_8$ gas flow rate of 2 sccm and 30 W of plasma power as a function of substrate temperature. The thickness of film was measured by a spectroscopic ellipsometry. These films were left in a vacuum oven of 100, 200 and $300^{\circ}C$ for a week. The change of film thickness, contact angle and adhesion and friction force was measured before and after the thermal test. No degradation of film was observed when films were treated at $100^{\circ}C$. The heat treatment of films at 200 and $300^{\circ}C$ caused the reduction of contact angles and film thickness in both silicon and oxide samples. Higher adhesion and friction forces of films were also measured on films treated at higher temperatures than $100^{\circ}C$. No differences on film properties were found when films were deposited on either silicon or oxide. A 100 nm silicon template with 1 to $500\;{\mu}m$ patterns was used for the hot embossing process on $4.5\;{\mu}m$ thick PMMA spun coated silicon wafers. The antistiction layer of 10 nm was deposited on the silicon mold. No stiction or damages were found on PMMA surfaces even after 30 times of hot embossing at $200^{\circ}C$ and 10 kN.