• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.100-100
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• 2016

물리기상증착방법 (Physical vapor deposition)에 의하여 합성된 천이금속 질화물 박막은 경도, 내마모성 등 절삭공구의 성능을 향상시키며, Ti-Al-N, Ti-Zr-N, Zr-Al-N, Cr-Si-N 등의 3원계 경질 박막에 대한 연구가 지속적으로 이루어지고 있다. 이중에서도 CrAlN 코팅은 높은 경도, 낮은 표면 조도 등의 우수한 기계적 특성 이외에 고온에서 안정한 합금상 형성으로 인하여 우수한 내열성을 보유하여 공구 코팅으로의 적용 가능성이 크다. 그러나 최근 공구사용 환경의 가혹화로 인하여 코팅의 내마모성 및 내열성 등의 물성 향상을 통한 공구의 수명 향상이 필요시 되고 있으며, 코팅에 적합한 중간층을 합성함으로써 공구 코팅으로의 적용 가능성을 높이는 연구들이 진행되고 있다. 본 연구에서는 CrAlN 코팅의 물성을 향상시키기 위해 CrAlN 코팅과 WC-Co 6wt.% 모재 사이에 CrN, CrZrN, CrN/CrZrSiN 등의 다양한 중간층을 합성하였으며, 중간층을 포함한 모든 코팅의 두께는 $3{\mu}m$ 로 제어하였다. 합성된 코팅의 미세조직, 경도 및 탄성계수, 내모성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, ball-on-disk 마모시험기 및 ${\alpha}-step$을 사용하였다. 코팅의 내열성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 500, 600, 700, 800, 900, $1,000^{\circ}C$로 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였다. CrAlN 코팅을 나노 인덴테이션으로 분석한 결과, 모든 코팅의 경도(35.5-36.2 GPa)와 탄성계수(424.3-429.2 GPa)는 중간층의 종류에 상관없이 비슷한 값을 보인 것으로 확인됐다. 그러나, 코팅의 마찰계수는 중간층의 종류에 따라 다른 값을 보였으며, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 마찰계수는 0.34로 CrZrN 중간층을 증착한 CrAlN 코팅의 마찰계수(0.41)에 비해 낮은 값을 보였다. 또한, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아, CrN/CrZrSiN 중간층을 합성한 CrAlN 코팅의 내마모성이 상대적으로 우수한 것으로 판단된다. 이것은 중간층의 H/E ratio가 코팅의 내마모성에 미치는 영향에 의한 결과로 사료된다. H/E ratio는 파단시의 최대 탄성 변형율로써, 모재/중간층/코팅의 H/E ratio 구배에 따라 코팅 내의 응력의 완화 정도가 변하게 된다. WC 모재 (H/E=0.040)와 CrAlN 코팅(H/E=0.089) 사이에서 CrN, CrZrSiN 중간층의 H/E ratio 는 각각 0.076, 0.083 으로 모재/중간층/코팅의 H/E ratio 구배가 점차 증가함을 확인 할 수 있었고, 일정 응력이 지속적으로 가해지면서 진행되는 마모시험중에 CrN과 CrZrSiN 중간층이 WC와 CrAlN 코팅 사이에서 코팅 내부의 응력구배를 완화시키는 역할을 함으로써 CrAlN 코팅의 내마모성이 향상된 것으로 판단된다. 모든 코팅을 열처리 후 경도 분석결과, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었고, 이는 CrZrSiN 중간층 내에 존재하는 $SiN_x$ 비정질상의 우수한 내산화성에 의한 결과로 판단된다.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.43-48
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• 2024

The discovery of a two-dimensional electron gas (2DEG) at the interface of LaAlO₃ (LAO) and SrTiO₃ (STO) substrates has sparked significant interest, providing a foundation for cutting-edge research in electronic devices based on complex oxide heterostructures. However, conventional methods for producing LAO thin films, typically employing techniques like pulsed laser deposition (PLD) within physical vapor deposition (PVD), are associated with high costs and challenges in precisely controlling the La and Al composition within LAO. In this study, we adopted a cost-effective alternative approach-solution-based processing-to fabricate LAO thin films and investigated their electrical properties. By adjusting the concentration of the precursor solution, we varied the thickness of LAO films from 2 to 65 nm and determined the sheet resistance and carrier density for each thickness. After vacuum annealing, the sheet resistance of the conductive channel ranged from 0.015 to 0.020 Ω·s^-1, indicating that electron conduction occurs not only at the LAO/STO interface but also into the STO bulk region, consistent with previous studies. These findings demonstrate the successful formation and control of 2DEG through solution-based processing, offering the potential to reduce process costs and broaden the scope of applications in electronic device manufacturing.

• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.209-231
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• 1999

Even though titanium(Ti) and its alloys are the most used dental implant materials, there are some problems that Ti wears easily and interferes normal osteogenesis due to the metal ions. Ti coated with bioactive ceramics such as hydroxyapatite has also such problems as the exfoliation or resorption of the coated layer, Recent studies on implant materials have been proceeding to improve physical properties of the implant substrate and biocompatibility of the implant surfaces. The purpose of the present study was to examine the physical property and bone tissue compatibility of bioinert nitrides ion plated Ti, Button type specimens(14mm in diameter, 2.32rrun in height) for the abrasion test and cytotoxicity test and thread type implants(3.75mm in diameter, 6mm in length) for the animal experiments were made from Ti(grade 2) and 316LVM stainless steel. Ti specimens were ion plated with TiN, ZrN by the low temperature arc vapor deposition, and the depth profile of the TiN/Ti, ZrN/Ti ion plated surface was examined by Auger Electron Spectroscopy. Three kind of button type specimens .of TiN/Ti, ZrN/Ti and Ti were used for abrasion test, and HEPAlClC7 cells and CCD cells were cultivated for 4 days with the specimens for cytotoxicity test. Thread type implants of TiN/Ti, ZrN/Ti, Ti, 316LVM were implanted on the femur of 6 adult dogs weighing 10kg-13kg. Two dogs were sacrified for histological examination after 45 days and 90 days, and four dogs were sacrified for the removal torque test of the implant') after 90 days. The removal torque force was measured by Autograph (Shimadzu Co., AGS-1000D series, Japan). Abrasion resistance of TiN/Ti was the highest, and that of ZrN/Ti and Ti were followed. The bioinert nitride ion plated Ti had much better abrasion resistance, compared with Ti, In the cytotoxicity test, the number of both cells were increased in all specimens, and there were no significant difference in cytotoxic reaction among all groups (p>0.1), In histological examination, 316LVM showed the soft tissue engagement in interface between the implant and bone, but the other materials after 45 days noted immature new bone formation in the medullary portion along the implant surface, and those after 90 days showed implant support by new bone formation in both the cortical and the medullary portion, The removal torque force of Tilv/Ti showed significantly higher than that of Ti(p(O,05). The difference in removal torque force between TiN/Ti and ZrN/Ti was not significant(p>0.05), and that of 316LVM was lowest among all groups(p<0.05). These results suggest that bioinert nitrides ion plated Ti can resolve the existing problems of Ti and bioactive ceramics, and it may be clinically applicable to human.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.239-240
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• 2008

As semiconductor devices are scaled down for better performance and more functionality, the Cu-based interconnects suffer from the increase of the resistivity of the Cu wires. The resistivity increase, which is attributed to the electron scattering from grain boundaries and interfaces, needs to be addressed in order to further scale down semiconductor devices [1]. The increase in the resistivity of the interconnect can be alleviated by increasing the grain size of electroplating (EP)-Cu or by modifying the Cu surface [1]. Another possible solution is to maximize the portion of the EP-Cu volume in the vias or damascene structures with the conformal diffusion barrier and seed layer by optimizing their deposition processes during Cu interconnect fabrication, which are currently ionized physical vapor deposition (IPVD)-based Ta/TaN bilayer and IPVD-Cu, respectively. The use of in-situ etching, during IPVD of the barrier or the seed layer, has been effective in enlarging the trench volume where the Cu is filled, resulting in improved reliability and performance of the Cu-based interconnect. However, the application of IPVD technology is expected to be limited eventually because of poor sidewall step coverage and the narrow top part of the damascene structures. Recently, Ru has been suggested as a diffusion barrier that is compatible with the direct plating of Cu [2-3]. A single-layer diffusion barrier for the direct plating of Cu is desirable to optimize the resistance of the Cu interconnects because it eliminates the Cu-seed layer. However, previous studies have shown that the Ru by itself is not a suitable diffusion barrier for Cu metallization [4-6]. Thus, the diffusion barrier performance of the Ru film should be improved in order for it to be successfully incorporated as a seed layer/barrier layer for the direct plating of Cu. The improvement of its barrier performance, by modifying the Ru microstructure from columnar to amorphous (by incorporating the N into Ru during PVD), has been previously reported [7]. Another approach for improving the barrier performance of the Ru film is to use Ru as a just seed layer and combine it with superior materials to function as a diffusion barrier against the Cu. A RulTaN bilayer prepared by PVD has recently been suggested as a seed layer/diffusion barrier for Cu. This bilayer was stable between the Cu and Si after annealing at $700^{\circ}C$ for I min [8]. Although these reports dealt with the possible applications of Ru for Cu metallization, cases where the Ru film was prepared by atomic layer deposition (ALD) have not been identified. These are important because of ALD's excellent conformality. In this study, a bilayer diffusion barrier of Ru/TaCN prepared by ALD was investigated. As the addition of the third element into the transition metal nitride disrupts the crystal lattice and leads to the formation of a stable ternary amorphous material, as indicated by Nicolet [9], ALD-TaCN is expected to improve the diffusion barrier performance of the ALD-Ru against Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru$(EtCp)_2$] and $NH_3$plasma and TaCN by a sequential supply of $(NEt_2)_3Ta=Nbu^t$ (tert-butylimido-trisdiethylamido-tantalum, TBTDET) and $H_2$ plasma. Sheet resistance measurements, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES) analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and $550^{\circ}C$ for 30 min, respectively. This is found to be due to the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to it having an amorphous structure. A 5-nm-thick ALD-TaCN film was even stable up to annealing at $650^{\circ}C$ between Cu and Si. Transmission electron microscopy (TEM) investigation combined with energy dispersive spectroscopy (EDS) analysis revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.4
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• pp.183-189
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• 2012

Surface treatments and their effects on high temperature properties for the Hastelloy X, which is a promising candidate alloy for high temperature heat-transport system, have been evaluated. For TiAlN and $Al_2O_3$ overlay coatings, the two different PVD (physical vapor deposition) methods using an arc discharge and a sputtering, were applied, respectively. In addition, a different surface treatment method of the diffusion coating by a pack cementation of Al (aluminiding) was also adopted in this study. To achieve enhanced thermal oxidation resistance at $1000^{\circ}C$ by suppressing the inhomogeneous formation of thick $Cr_2O_3$ crust at the surface region, a study for the surface modification methods on the morphological and structural properties of Hastelloy X substrates has been conducted. The structural and compositional properties of each sample were characterized before and after heat-treatment at $1000^{\circ}C$ under air and He environment. The results showed that the Al diffusion coating showed the more enhanced high temperature properties than the overlay coatings such as the suppressed thick $Cr_2O_3$ crust formation and lower wear loss.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.642-642
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• 2013

Graphene, two dimensional single layer of carbon atoms, has tremendous attention due to its superior property such as high electron mobility, high thermal conductivity and optical transparency. Especially, chemical vapor deposition (CVD) grown graphene has been used as a promising material for high quality and large-scale graphene film. Unfortunately, although CVD-grown graphene has strong advantages, application of the CVD-grown graphene is limited due to ineffective transfer process that delivers the graphene onto a desired substrate by using polymer support layer such as PMMA(polymethyl methacrylate). The transferred CVD-grown graphene has serious drawback due to remaining polymeric residues generated during transfer process, which induces the poor physical and electrical characteristics by a p-doping effect and impurity scattering. To solve such issue incurred during polymer transfer process of CVD-grown graphene, various approaches including thermal annealing, chemical cleaning, mechanical cleaning have been tried but were not successful in getting rid of polymeric residues. On the other hand, lithographical patterning of graphene is an essential step in any form of microelectronic processing and most of conventional lithographic techniques employ photoresist for the definition of graphene patterns on substrates. But, application of photoresist is undesirable because of the presence of residual polymers that contaminate the graphene surface consistent with the effects generated during transfer process. Therefore, in order to fully utilize the excellent properties of CVD-grown graphene, new approach of transfer and patterning techniques which can avoid polymeric residue problem needs to be developed. In this work, we carried out transfer and patterning process simultaneously with no polymeric residue by using a metal etch mask. The patterned thin gold layer was deposited on CVD-grown graphene instead of photoresists in order to make much cleaner and smoother surface and then transferred onto a desired substrate with PMMA, which does not directly contact with graphene surface. We compare the surface properties and patterning morphology of graphene by scanning electron microscopy (SEM), atomic force microscopy(AFM) and Raman spectroscopy. Comparison with the effect of residual polymer and metal on performance of graphene FET will be discussed.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.6
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• pp.740-750
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• 2006

Statement of problems. In an attempt to reduce screw loosening, dry lubricant coatings such as pure gold or tefron have been applied to the abutment screw. However, under repeated tightening and loosening procedures, low wear resistance and adhesion strength of coating material produced free particles on the surface of abutment screw and increased frictional resistance resulting in screw tightening problems. Purpose. The aim of this study was to compare friction coefficient, adhesion strength, vickers hardness and evaluate coating surface of titanium alloy specimens coated with TiN(titanium nitride), ZrN(zirconium nitride) and WC(tungsten carbide). Material and method. Titanium alloy(Ti-6Al-4V) discs of 12mm in diameter and 1mm in thickness divided into 4 groups. TiN, ZrN and WC was coated for the specimens of 3 groups respectively, and those of 1 group were not coated. Each group was made up of 4 specimens. In this study, sputtering method was used among the PVD(Physical Vapor Deposition) techniques available for TiN, ZrN and WC coatings. Friction coefficient, adhesion strength, vickers hardness and coating surface of 4 groups were measured. Results. 1. For all three coating conditions, friction coefficient was significantly decreased. Especially, ZrN coated surface showed the lowest value. $TiN(0.39{\pm}0.02)$, $ZrN(0.24{\pm}0.01)$, $WC(0.31{\pm}0.03)$. 2. TiN coating showed the highest adhesion strength, however ZrN coating had the lowest value. $TiN(25.3N{\pm}1.6)$, $ZrN(14.8N{\pm}0.6)$, $ WC(18.4N{\pm}0.7)$. 3. Vickers hardness of all three coatings was remarkably increased as compared with that of none coated specimen. TiN coating had the highest Vickers hardness, however WC coating showed the lowest value. $TiN(1865.2{\pm}33.8)$, $ZrN(1814.4{\pm}18.6)$, $WC(1008.5{\pm}35.9)$. 4. The ZrN or WC coated specimen showed a homogeneous and smooth surface, however the rough surface with defects was observed for TiN coating. Conclusions. When TiN, ZrN and WC coating applied to the abutment screw, frictional resistance would be reduced, as a result, the greater preload and prevention of the screw loosening could be expected.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.122-122
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• 1999

Graphite with its advantages of high thermal conductivity, low thermal expansion coefficient, and low elasticity, has been widely used as a structural material for high temperature. However, graphite can easily react with oxygen at even low temperature as 40$0^{\circ}C$, resulting in CO2 formation. In order to apply the graphite to high temperature structural material, therefore, it is necessary to improve its oxidation resistive property. Silicon Carbide (SiC) is a semiconductor material for high-temperature, radiation-resistant, and high power/high frequency electronic devices due to its excellent properties. Conventional chemical vapor deposited SiC films has also been widely used as a coating materials for structural applications because of its outstanding properties such as high thermal conductivity, high microhardness, good chemical resistant for oxidation. Therefore, SiC with similar thermal expansion coefficient as graphite is recently considered to be a g행 candidate material for protective coating operating at high temperature, corrosive, and high-wear environments. Due to large lattice mismatch (~50%), however, it was very difficult to grow thick SiC layer on graphite surface. In theis study, we have deposited thick SiC thin films on graphite substrates at temperature range of 700-85$0^{\circ}C$ using single molecular precursors by both thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating . Two organosilicon compounds such as diethylmethylsilane (EDMS), (Et)2SiH(CH3), and hexamethyldisilane (HMDS),(CH3)Si-Si(CH3)3, were utilized as single source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cubic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 80$0^{\circ}C$ from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtained with either HMDS or DMS at 85$0^{\circ}C$. We compared the difference of crystal quality and physical properties of the PEMOCVD was highly effective process in improving the characteristics of the a SiC protective layers grown by thermal MOCVD and PEMOCVD method and confirmed that PEMOCVD was highly effective process in improving the characteristics of the SiC layer properties compared to those grown by thermal MOCVD. The as-grown samples were characterized in situ with OES and RGA and ex situ with XRD, XPS, and SEM. The mechanical and oxidation-resistant properties have been checked. The optimum SiC film was obtained at 85$0^{\circ}C$ and RF power of 200W. The maximum deposition rate and microhardness are 2$mu extrm{m}$/h and 4,336kg/mm2 Hv, respectively. The hardness was strongly influenced with the stoichiometry of SiC protective layers.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.227-232
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• 2012

Inconel 617 and Hastelloy X are the most promising candidate materials for the heat exchanger of next generation nuclear reactor. Surface coating and its effects on high temperature properties for the Inconel 617 and Hastelloy X under molten FLiNaK (LiF-NaF-KF) salt environment have been investigated. For TiAlN and $Al_2O_3$ overlay coatings, the two different PVD (physical vapor deposition) methods of an arc discharge and a sputtering were applied, respectively. A study for the thermal stability of the surface modified Ni-Cr alloy substrates has been conducted. To evaluate the corrosion mechanism of Ni-Cr alloys in the molten salt, a ruptured Inconel pipe used for the molten salt transportation has been analyzed. The thermal properties of morphological and structural properties each sample were characterized before and after heat-treatment at $600^{\circ}C$ in molten FLiNaK salt. The results showed that the TiAlN and $Al_2O_3$ overlay coated specimens had the enhanced high temperature stability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.788-795
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• 2013

A magnesium bipolar plate whose surface was protected by thinly deposited silver layer was investigated as an alternative to existing graphite bipolar plate of PEM fuel cells. Thin silver layer of $3{\mu}m$ was deposited on a magnesium alloy substrate by physical vapor deposition (PVD) method in an environment of $180^{\circ}C$. A number of tests were conducted on the fabricated magnesium based bipolar plates to determine their suitability for use in PEM fuel cell stacks. The test on corrosion resistance in the same pH condition as in a PEM operation demonstrated the layer protected the magnesium alloy substrate, while unprotected substrate suffered from severe corrosion. The contact resistance of the fabricated bipolar plate was less than $20m{\Omega}-cm^2$ which was superior to the conventional bipolar plates. A single cell was constructed using the fabricated bipolar plates and power output was measured. Due to the enhanced conductivity caused by low contact resistance, slight increase was observed in current density and output voltage. With low density of the magnesium substrate and ease on machining, the weight reduction of the stack of 30~40 % is possible to produce the same power output.