• Journal of Powder Materials
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• v.20 no.4
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• pp.245-252
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• 2013

This study attempted to manufacture a Cu-Ga coating layer via the cold spray process and to investigate the applicability of the layer as a sputtering target material. In addition, changes made to the microstructure and properties of the layer due to annealing heat treatment were evaluated, compared, and analyzed. The results showed that coating layers with a thickness of 520 mm could be manufactured via the cold spray process under optimal conditions. With the Cu-Ga coating layer, the ${\alpha}$-Cu and $Cu_3Ga$ were found to exist inside the layer regardless of annealing heat treatment. The microstructure that was minute and inhomogeneous prior to thermal treatment changed to homogeneous and dense with a more clear division of phases. A sputtering test was actually conducted using the sputtering target Cu-Ga coating layer (~2 mm thickness) that was additionally manufactured via the cold-spray coating process. Consequently, this test result confirmed that the cold sprayed Cu-Ga coating layer may be applied as a sputtering target material.

• Journal of Powder Materials
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• v.18 no.6
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• pp.552-561
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• 2011

This study attempted to manufacture a Cu-15 at.%Ga coating layer via the cold spray process and investigated the effect of heat treatment environment on the properties of cold sprayed coating material. Three kinds of heat treatment environments, $5%H_2$+argon, pure argon, and vacuum were used in this study. Annealing treatments were conducted at $200{\sim}800^{\circ}C$/1 hr. With the cold sprayed coating layer, pure ${\alpha}$-Cu and small amounts of $Ga_2O_3$ were detected in the XRD, EDS, EPMA analyses. Porosity significantly decreased and hardness also decreased with increasing annealing temperature. The inhomogeneous dendritic microstructure of cold sprayed coating material changed to the homogeneous and dense one (microstructural evolution) with annealing heat treatment. Oxides near the interface of particles could be reduced by heat treatment especially in vacuum and argon environments. Vacuum environment during heat treatment was suggested to be most effective one to improve the densification and purification properties of cold sprayed Cu-15 at.%Ga coating material.

• Korean Journal of Materials Research
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• v.13 no.4
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• pp.205-212
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• 2003

RF sputtering process was applied to produce thin hydroxyapatite［HA, Ca10($PO_4$)$_{6}$ $ (OH)_2$films on Ti-6Al-4V alloy substrates. To make a 101.6 mm dia.${\times}$5 mm HA target, the commercial HA powder was first calcinated for 3h at $200^{\circ}C$. A certain amount of the calcinated HA powder was pressed under a pressure of 20,000 psi by the cold isostatic press(CIP) and the pressed HA target was sintered for 6 h at $1,200^{\circ}C$. The effects of different heat treating conditions on the bonding strength between HA thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the alloy substrates were annealed for 1 h at $850^{\circ}C$ under $3.0${\times}$10^{-3}$ Xtorr, and after deposition, the hydroxyapatite/Ti-6Al-4V alloy thin films were annealed for 1 h at 400, 600 and $800^{\circ}C$ under the atmosphere, respectively. Experimental results represented that the HA thin films on the annealed substrates had higher hardness than non-heat treated substrates before the deposition.

• Corrosion Science and Technology
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• v.3 no.4
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• pp.148-153
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• 2004

Magnesium thin flims were prepared on cold-rolled steel substrates by RF magnetron sputtering technique. The influence of argon gas pressure and substrate bias voltage on their crystal orientation and morphology of the coated films were investigated by scanning electron microscopy (SEM) and X-ray diffraction, respectively. And the effect of crystal orientation and morphology of magnesium films on corrosion behaviors was estimated by measuring anodic polarization curves in deaerated 3%NaCl solution. From the experimental results, all the sputtered magnesium films showed obviously good corrosion resistance to compare with 99.99% magnesium target of the sputter-evaporation metal. Finally it was shown that the Corrosion-resistance of magnesium films can be improved greatly by controlling the crystal orientation and morphology with effective use of the plasma sputtering technique.

• Journal of Biomedical Engineering Research
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• v.30 no.3
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• pp.199-204
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• 2009

Iridium oxide films (IROFs) have been extensively studied as a material for electrical stimulation of neurons, as iridium oxide has higher charge storage capacity than other metal films. More recently, sputtered iridium oxide film (SIROF) has been studied, because it can be made more conveniently than activated iridium oxide film (AIROF). Typically, the SIROFs are grown at temperatures from 400 to 600 $^{\circ}C$. However, such high temperatures cannot be used when the iridium oxide (IrOx) film is to be deposited on a flexible polymer material, such as polyimide. In this paper, we show that we can still obtain excellent characteristics in SIROFs grown without heating (cold SIROF), by optimizing the growth conditions. We show that the oxygen flow rate is a critical parameter for controlling the surface properties of a cold SIROF. At an oxygen flow rate of 12 seem, the cold SIROF exhibited a charge storage capacity (CSC) of 60 mC/cm$^2$, which is comparable to or better than other published values for iridium oxide films including heated SIROFs. The film produced under these conditions also had the minimum impedance value of all cold SIROFs deposited for this study. A stability test and biocompatibility test also demonstrated the superiority of the optimized cold SIROF.

• Journal of the Korean institute of surface engineering
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• v.41 no.5
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• pp.205-213
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• 2008

A 3D particle code is developed to analyze electron behavior in a planar magnetron sputtering cathode either in balanced or unbalanced configuration. Three types of collisions are included; electron - neutral elastic, excitation to a metastable state and ionization. Flight path is calculated by a 4-th order Runge-Kutta method with a time step of 10 ps. Effects of electron starting position, magnetic field intensity and configuration were analyzed. For a more efficient and accurate modeling, multithreading technique is considered for multicore CPU computers. Under an assumption of cold ion approach, target erosion profiles are predicted for a flat target surface.

• Journal of Powder Materials
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• v.23 no.1
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• pp.21-25
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• 2016

The microstructural properties and electrical characteristics of sputtering films deposited with a Cu-Ga target are analyzed. The Cu-Ga target is prepared using the cold spray process and shows generally uniform composition distributions, as suggested by secondary ion mass spectrometer (SIMS) data. Characteristics of the sputtered Cu-Ga films are investigated at three positions (top, center and bottom) of the Cu-Ga target by X-ray diffraction (XRD), SIMS, 4-point probe and transmission electron microscopy (TEM) analysis methods. The results show that the Cu-Ga films are composed of hexagonal and unknown phases, and they have similar distributions of composition and resistivity at the top, center, and bottom regions of the Cu-Ga target. It demonstrates that these films have uniform properties regardless of the position on the Cu-Ga target. In conclusion, the cold spray process is expected to be a useful method for preparing sputter targets.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.15-16
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• 2008

In case manufacturing COF, through hole should be made to be used for a pathway connecting the conductive layers of its both faces. In case Cu-plating inside of through hole with electroless plating way, contact between Cu and PI film gets bad to be fell apart from PI by the impact of applying to the electric devices. Therefore, after sputtering is applying on inner through hole, then a method to perform electroplating process. In this study, after changing sputtering condition to manufacture FCCL, we looked the changeability of the upper PI and inner hole Cu layers. Making use of RF Magnetron sputtering equipment, we coated Cu thin film and Cu-plated on it through electroplating. After cold-mounting the completed FCCL, we examined hole section through an optical microscope. From the result of test, with parameters deposition pressure and deposition time, both the thickness of the hole plated layer and PI plated upper layer increased at regular rate, increasing the thickness of Cu sputter layer. However, from the result of test in increasing RF-power, we could know the increment rate of hole plated layer is considerably greater than that of PI plated upper layer. Therefore, we finally acquired good result; if you want only to increase the plated layer of inner hole, it's much better to increase RF-power.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.37-38
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• 2011

알루미늄은 높은 내부식성과 우수한 물리적 특성으로 철강 제품의 부식방지를 위한 표면처리와 항공 우주분야 소재로 각광을 받아왔다. 알루미늄을 철강 제품의 부식방지를 위한 표면처리 소재로 사용되는 경우 비교적 두껍게(15 ${\mu}m$ 이상) 코팅된다. 본 연구에서는 얇은 두께(3 ${\mu}m$ 이하)의 알루미늄 박막을 이용하여 높은 내식성을 갖는 코팅 공정을 개발하고자 한다. 물리기상증착으로 코팅되는 대부분의 금속은 주상정 구조를 갖는다. 주상정 구조는 grain boundary에 공극이 존재하고, 이 공극을 통해서 부식을 일으키는 물질이 보호막과 모재의 계면으로 침투하여 모재가 부식을 일으킨다. 스퍼터링 공정을 제어하여 알루미늄 박막의 공극 발생을 억제하여 보호막으로서의 기능을 향상할 수 있는 방법을 제안한다. 알루미늄 코팅을 위해서 magnetron sputtering을 이용하였으며, 기판은 냉연강판을 사용하였다. 냉연강판위에 코팅된 알루미늄 박막을 분석한 결과, 스퍼터링 소스에 역방향 자기장을 인가하여 코팅한 알루미늄 박막이 염수분무 120 시간 후에도 적청이 발생하지 않는 우수한 내식성을 보였다.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1459-1462
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• 2007

In general a thermoelectric cooler (TEC) consists of a series of P type and N type thermoelectric materials sandwiched between two wafers. When a DC current passes through these materials, three different effects take place; Peltier effect, Joule heating effect and heat transfer by conduction due to temperature difference between hot and cold plates. In this study we have developed a micro TEC using $Bi_2Te_3$ (N type) and $Bi_{0.5}Sb_{1.5}Te_3$ (P type) thin films. In order to improve that performance of a micro TEC, we made 10 um height TE legs using special PR only for lift-off. We measured COP (coefficient of performance) and temperature difference between hot and cold connectors with current.