• 한국표면공학회지
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• 제20권3호
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• pp.106-117
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• 1987

The microhardness and the structural characteristics of the chemically vapor deposited TiN film on the 430 stainless steel substrate have been investigated with various deposition parameters such as the deposition time, the total flow rate, the flow rate ratio $(H_2/N_2)$, and the deposition temperature. The most important factor to affect the microhardness of the TiN film in this study was the denseness of the structure in connection with the degree of the lattice strain. The relationship between the lattice parameter changes and the grain size variation under all deposition conditions generally followed the grain boundary relaxation model. The (111) preferred orientation prevailed in the early stage of the deposition conditions, however, the (200) preferred orientation was developed in the later stage. The surface morphology at optimum conditions displayed a dense diamond shaped structure and the microhardness of the films was high (1700-2400Hv) regardless of the type of the substrates used.

• 한국결정성장학회지
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• 제9권3호
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• pp.289-294
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• 1999

The charged clusters or particles, which contain hundreds to thousands of atoms or even more, are suggested to from in the gas phase in the thin film processes such as CVD, thermal evaporation, laser ablation, and flame deposition. All of these processes are also phase synthesis of the nanoparticels. Ion-induced or photo-induced nucleation is the main mechanism for the formation of these nanoclusters or nanoparticles in the gas phase. Charge clusters can make a dense film because of its self-organizing characteristics while neutral ones make a porous skeletal structure because of its Brownian coagulation. The charged cluster model can successfully explain the unusual phenomenon of simultaneous deposition and etching taking place in diamond and silicon CVD processes. It also provides a new interpretation on the selective deposition on a conducting material in the CVD process. The epitaxial sticking of the charged clusters on the growing surface is getting difficult as the cluster size increases, resulting in the nanostructure such as cauliflower or granular structures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 학술대회 및 기술세미나 논문집 디스플레이 광소자
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• pp.64-65
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• 2006

We studied the nematic liquid crystal (NLC) alignment capability by the IB(on bean) alignment method on a NDLC(Nitrogen Diamond Like Carbon) as a-C:H thin film, and investigated electro-optical performances of the IB aligned IPS(In plane switching}cell with NDLC surface. A good LC alignment by IB exposure on a NDLC surface was achieved. Monodomain alignment of the IB aligned IPS cell can be observed. The goodelectro-optical (EO) characteristics of the IB aligned IPS cell was observed with oblique IB exposure on the NDLC as a-C:H thin film for 1 min.

• 열처리공학회지
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• 제32권4호
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• pp.155-160
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• 2019

Diamond Like Carbon (DLC) is a metastable form of amorphous carbon that have superior material properties such as high mechanical hardness, chemical inertness, abrasion resistance, and biocompatibility. Furthermore, its material properties can be tuned by additional doping such as nitrogen or boron. However, either pure DLC or doped DLC show poor adhesion property that makes it difficult to apply contact processing technique. Therefore we propose ultrafast laser micromachining which is non-contact precision process without mechanical degradation. In this study, we developed precision machining process of DLC thin film using an ultrafast laser by investigating the process window in terms of laser fluence and laser wavelength. We have also demonstrated various patterns on the film without generating any microcracks and debris.

• Tribology and Lubricants
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• 제33권4호
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• pp.127-133
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• 2017

In order to characterize the adhesive properties and failure mechanisms of diamond-like carbon (DLC) films of two different thicknesses (130 nm and $1.2{\mu}m$), deposited by plasma-enhanced chemical vapor deposition on a Si substrate, scratch testing with a micro-indenter ($12.5{\mu}m$ tip radius) was performed under a linearly increasing load. These scratch tests were conducted under the same test conditions for both films. The critical load of each film was estimated from the scratch test results, based on a sharp increase in the coefficient of friction and a clear distinction of failure modes. The critical load was the basis for evaluating the adhesion strength of the films, and the $1.2{\mu}m-thick$ DLC film had superior adhesion strength. For better understanding of the failure modes, the following analyses were conducted: friction behavior and scratch tracks analysis using scanning electron microscopy, energy-dispersive spectroscopy, and 3-D profilometry. The scratch test results showed that failure modes were related to the thickness of the films. The 130 nm-thick DLC film underwent cohesive failure modes (cracks and chipping) before reaching to a gross failure stage. On the other hand, the thicker DLC film ($1.2{\mu}m-thick$) did not exhibit micro cracks before a sudden gross failure of the film together with the evidence of cracking and chipping of the Si substrate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.135-135
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• 1999

It is well known that Raman spectroscopy is powerful tool in analysis of sp3/sp3 bonding fraction in diamond-like carbon(DLC) films. Raman spectra of DLC film is composed of D-peak centered at 1350cm-1 and G-peak centered at 1530cm-1. The sp3/sp3 fraction is qualitatively acquired by deconvolution method. However, in case of DLC film, it is generally observed that G-peak position shifts toward low wavenumber as th sp3 fraction increases. However, opposite results were frequently observed in ta-C films. ta-C film has much higher residual compressive stress due to its high sp3 fraction compared to the DLC films deposited by CVD method. Effect of residual stress on G-peak position is most recommendable parameter in Raman analysis of ta-C, due to its smallest fitting error among many parameters acquired by peak deconvolution of symmetric spectra. In current study, the effect of residual stress on Raman spectra was quantitatively evaluated by free-hang method. ta-C films of different residual stress were deposited on Si-wafer by modifying DC-bias voltage during deposition. The variation of the G-peak position along the etching depth were observed in the free-hangs of 20~30${\mu}{\textrm}{m}$ etching depth. Mathematical result based on Airy stress function, was compared with experimental results. The more reliable analysis excluding stress-induced shift was possible by elimination of the Raman shift due to residual compressiove stress.

• 한국전기전자재료학회논문지
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• 제17권10호
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• pp.1100-1106
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• 2004

In this paper, we intend to make fringe-field switching (FFS) mode cell by the ion beam (IB) alignment method on the a-C：H thin film, to analyze electro-optical characteristics in this cell. We studied on the suitable inorganic thin film for fringe-field switching (FFS) cell and the aligning capabilities of nematic liquid crystal (NLC) using the alignment material of a-C：H thin film as working gas at 30 W rf bias condition. A high pretilt angle of about 5 $^{\circ}C$ by ion beam (IB) exposure on the a-C：H thin film surface was measured. Consequently, the high pretilt angle and the good thermal stability of LC alignment by the IB alignment method on the a-C：H thin film surface as working gas at 30 W rf bias condition can be achieved. An excellent voltage-transmittance (V -T) and response time curve of the IE-aligned FFS-LCD was observed with oblique IB exposure on the a-C：H thin films. Also, AC V-T hysteresis characteristics of the IB-aligned FFS-LCD with IE exposure on the a-C：H thin films is almost the same as that of the rubbing-aligned FFS cell on a polyimide (PI) surface.

• 열처리공학회지
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• 제31권4호
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• pp.187-193
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• 2018

In this study, the electrical conductivity, transmittance and gas barrier properties of diamond-like carbon (DLC) thin films were studied. DLC is an insulator, and has transmittance and oxygen gas barrier properties varying depending on the thickness of the thin film. Recently, many researchers have been trying to apply DLC properties to specific industrial conditions. The DLC thin films were deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition) process. The doping gas was used for the DLC film to have electrical conductivity, and the optimum conditions of transmittance and gas barrier properties were established by adjusting the gas ratio and DLC thickness. In order to improve the electrical conductivity of the DLC thin film, $N_2$ doping gas was used for $CH_4$ or $C_2H_2$ gas. Then, a heat treatment process was performed for 30 minutes in a box furnace set at $200^{\circ}C$. The lowest sheet resistance value of the DLC film was found to be $18.11k{\Omega}/cm^2$. On the other hand, the maximum transmittance of the DLC film deposited on the PET substrate was 98.8%, and the minimum oxygen transmission rate (OTR) of the DLC film of $C_2H_2$ gas was 0.83.

• 한국진공학회지
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• 제15권3호
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• pp.287-293
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• 2006

R.F. PACVD법을 이용하여, 벤젠을 반응기체로 사용하여 순수한 DLC필름을 증착하였다. DLC필름의 마찰마모특성은 시험 환경을 제어하기 위하여 챔버로 고립된 ball-on-disk형식의 마모시험기를 이용하여 측정하였다. 상대습도에 따른 필름의 마찰특성을 관찰하기 위하여, 상압에서 챔버 내의 습도를 0-90%로 조절하면서 관찰하였다. 그리고 상대면 물질의 영향을 알아보기 위하여 스틸볼과 함께 DLC필름이 코팅된 스틸볼을 사용하였다. 스틸볼을 사용시 습도가 0%에서 90%로 증가함에 따라 마찰계수가 0.025에서 0.2로 크게 증가하였다. Ferich debris가 생성되지 않는 DLC가 코팅된 볼을 사용하여 실험한 경우에, 마찰계수는 상대 습도가 90%인 경우에도 0.08정도로, 스틸볼을 사용하였을 경우보다 훨씬 더 낮은 습도의존성을 보여주었다. 스틸볼 사용시 나타나는 DLC필름의 마찰계수의 큰 습도의존성은 습도가 증가함에 따라 debris의 크기 증가와 함께 스틸볼의 마모로 인한 Fe-rich debris의 생성과 밀접한 관계가 있음을 확인 할 수 있었다. 그리고 스틸볼을 사용하여 90%의 습도에서 마모시험을 하는 중간에 습도를 0%로 변화시키며 관찰한 결과, 마찰계수 값이 급격히 감소하였다. 이와 같은 결과를 통하여, Fe-rich debris가 마찰계수에 미치는 영향은 debris내의 Fe원소가 습도에 매우 민감한 흑연상의 전이층을 형성시킨다는 것을 확인 할 수 있었다.

• 전기학회논문지
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• 제67권10호
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• pp.1375-1381
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• 2018

In this paper, we studied coatings of the DLC thin film for improving loosening torque of dental implant screw. We used a filtered arc ion plating process which can realize the most dense DLC layer by coating the DLC thin film on the surface of the dental abutment screw. It showed both hardness comparable to diamond and low friction coefficient similar to graphite, and to improve the loosening phenomenon by increasing the screw tightening force Cr/CrN, Ti/TiN or Ti/TiN/Cr/CrN buffer layers were deposited for 5 to 10 minutes to improve the adhesion of the DLC thin film to the surface of the Ti (Gr.5), and then the DLC thin film was coated for about 15 minutes. As a result, the Cr/CrN buffer layer exhibited the highest hardness of 29.7 GPa, the adhesion of 18.62N on average, and a very low coefficient of friction of less than 0.2 as a whole. And we measured loosening torque after one million times with masticatory movement simulator. As a result, the values of the coated screw loosening torque were clearly higher than those of the uncoated screw. From this, it was found that the DLC coating was effective methods improving the loosening torque. In addition, it was confirmed that the cytotoxicity test and cell adhesion test showed high biocompatibility.