• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.273-273
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• 2008

This paper describes the frequency response of two-port surface acoustic wave (SAW) resonator made of 002-polycrystalline aluminum nitride (AlN) thin film on 111-poly 3C-SiC buffer layer. In there, Polycrystalline AlN thin films were deposited on polycrystalline 3C-SiC buffer layer by pulsed reactive magnetron sputtering system, the polycrystalline 3C-SiC was grown on $SiO_2$/Si sample by CVD. The obtained results such as the temperature coefficient of frequency (TCF) of the device is about from 15.9 to 18.5 ppm/$^{\circ}C$, the change in resonance frequency is approximately linear (30-$150^{\circ}C$), which resonance frequency of AlN/3C-SiC structure has high temperature stability. The characteristics of AlN thin films grown on 3C-SiC buffer layer are also evaluated by using the XRD, and AFM images.

• Journal of Magnetics
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• v.9 no.4
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• pp.116-120
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• 2004

Hexagonal barium-ferrite ($BaFe_{12}O_{19}$, magnetoplumbite structure; BaM) film with perpendicularly c-axis orientation was successfully deposited on (100) silicon substrates with an MgO (111) underlayer by rf diode sputtering and in-situ heating at $920^{\circ}C$. The magnetic and structural properties of 0.27 ${\mu}m$ thick BaM films on MgO (111) underlayers were compared to films of the same thickness deposited onto single-crystal MgO (111) and c-plane ($000{\ell}$) sapphire ($Al_2O_3$) substrates by vibrating sample magnetometry (VSM), x-ray diffractometer (XRD), and atomic force microscopy (AFM). The thickness dependence of MgO (111) underlayers on silicon wafer was found to have a large effect on both magnetic and structural properties of the BaM film. The thickness of 15 nm MgO (111) underlayers produced BaM films with almost identical magnetic and structural properties as the single-crystal substrates; this can be explained by the lower surface roughness for thinner underlayer thicknesses. The magnetization saturation ($M_s$) and the ratio $H_{cII}/H_{c{\bot}}$ for the BaM film with a 15 nm MgO (111) underlayer is 217 emu/cc and 0.24, respectively. This is similar to the results for the BaM films deposited on the single-crystal MgO (111) and sapphire substrates of 197 emu/cc and 0.10, 200 emu/cc and 0.12, respectively. Therefore, the proposed MgO (111) underlayer can be used in many applications to promote c-axis orientation without the cost of expensive substrates.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03a
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• pp.73-80
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• 1996

Commerical purity aluminium , copper and STS 304 stainless steel sheets are welded by ultrasonic welding. The microstructures, x-ray diffraction profiles of planes , pole figures of the surface of original metal sheets are compared with those of the weld interface. The microstructures show disturbance and dark areas in the weld interface and grain refinement in the vicinity of the interface. The x-ray diffraction intensity of each plane in weld interface decreased in all metal sheets with exception of 9200) in steel sheet. The microstructure and x-ray diffraction intensity is affected by the mixture of deformation, heating and vibratin duringthe ultrasonic welding. Therefore, after the ultrasonic welding, the positions of the peak intensity in the pole figures are changed, the value of the maximum pole intensity is decreased in Al, is increased in copper and stainless steel. Very strong {100} <001> texture, strong {100} <001>,{123}<634> textures in original Al surface are transformed into weak, {100}<001>, {110}<112> and {112}<111> components in weld surface, weak (110) fiber is slightly changed to (110) fiber in copper, (100)and ${\gamma}$ fiber components are transformed into strong ${\gamma}$ fiber component in stainless steel.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.163-163
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• 2003

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.552-552
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• 2013

In our study we consider Al2O3 ceramic substrates for Plasma Surface Treatments in order to improve deposited diamond surface and increase diamond deposition rate by applying DBD (Dielectric Barrier Dischrge) system. Because Plasma Surface Treatments was used as a modification method of material surface properties like surface free energy, wettability, and adhesion. By applying Plasma Surface Treatments diamond films are deposited on the Al2O3 ceramic substrates. DC Arc Plasmatron with mathane and hydrogen gases is used. Deposited diamond films are investigated by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy) and XRD (X-ray Diffractometer). Then the C-H stretching of synthetic diamond films by FTIR (Fourier Transform Infrared Spectroscopy) is studied. As a result, nanocrystalline diamond films were identified by using SEM and diamond properties in XRD peaks at (111, $43.8{\Box}$, (220, $75.3{\Box}$ and (311, $90.4{\Box}$ were shown. Absorption peaks in FTIR spectrum, caused by CHx sp3 bond stretching of CVD diamond films, were identified as well. Finally, we improved such parameters as depostion rate ($2.3{\mu}m$/h), diamond surface uniformity, and impurities level by applying Plasma Surface Treatments. These experimental results show the importance of Plasma Surface Treatments for diamond deposition by a plasma source.

• Journal of the Korean institute of surface engineering
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• v.50 no.6
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• pp.473-479
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• 2017

CrN coatings have been used as protective coatings for cutting tools, forming tools, and various tribological machining applications because these coatings have high hardness. Cr-Al-N coatings have been investigated to improve the properties of CrN coatings. Cr-Al-N coatings were fabricated by a hybrid physical vapor deposition method consisting of unbalanced magnetron sputtering and arc ion plating with different working pressure and substrate bias voltage. The phase analysis of the composition was performed using XRD (x-ray diffraction). Cr-Al-N coatings were grown with textured CrN phase and (111), (200), and (220) planes. The adhesion strength of the coatings tested by scratch test increased. The friction coefficient and removal rate of the coatings were measured by a ball-on-disk test. The friction coefficient and removal rate of the coatings decreased from 0.46. to 0.22, and from $2.00{\times}10^{-12}m^2/N$ to $1.31{\times}10^{-13}m^2/N$, respectively, with increasing bias voltage. The tribological properties of the coatings increased with increasing substrate bias voltage.

• Journal of Power System Engineering
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• v.7 no.2
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• pp.73-79
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• 2003

The present study was aimed at analysing the damage of a used gas turbine bucket after 39,500h of total service. Microstructures and cracks of service-induced bucket were observed. The crack might have initiated from the coating in the bucket surface by thermal fatigue and propagated into the GTD111 base metal. Maximum depth of penetration was 2.7 mm(full penetration) at the leading edge. Crack contains a lot of Cr-,Ti-,Al-oxide which will prohibit filling and wetting of insert metal. Depth and propagation direction of crack were accorded with centrifugal force and temperature distribution in turbine bucket. Present result will provide basic data for repair bonding process.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.105-109
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• 1997

The effects of surface conditions of the C-2 cemented carbide substrate on the adhesion of diamond film were investigated. The substrates were pretreated for different times with Murakami's reagent and then the acid solution of an H2SO4-H2O2. The adhesion strength was estimated by a peeling area around the Rockwell-A indentation. The cutting performance of the diamond-coated tools was evaluated by measuring flank wears in dry turning of Al-17% Si alloy. The morphology of deposited diamond crystallites was dominated by (111) and (220) surfaces with a cubooctahedral shape. The diamond film quality was hardly affected by the surface conditions of the substrate. The variation of tool life with longer substrate etching times resulted from a compromies between the increase of film adhesion at the interface and the decrease of toughness at the substrate surface. The coated tools were mainly deteriorated by chipping and flaking of the diamond film form a lock of adhesion strength, differently from the wear phenomena of PCD tools.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.111.2-111.2
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• 2012

정보 기술 시대에 맞춰 광전소자의 연구가 활발해지면서 투명전극으로 사용될 수 있는 Transparent Conductive Oxide (TCO) 재료에 대한 관심이 높아지고 있다. 하지만 TCO의 대표적인 물질인 Indium Tin Oxide (ITO)의 경우 In의 가격 상승으로 인해 최근에는 낮은 전도도와 높은 투과도를 가질 수 있는 대체 물질에 대한 연구가 활발히 진행되고 있다. 그 중에서 3.2 eV 의 높은 밴드갭을 갖는 ZnO 는 가시광선 영역에서 높은 투과율을 나타낼 뿐만 아니라 Al, Ga을 도핑함으로써 낮은 전도도를 가질 수 있다. 이러한 TCO 재료는 surface texturing을 통하여 optical region 에서 반사를 억제 시킴으로서 빛을 모으는 역할을 하여 태양전지의 효율을 향상 시킬 수 있기 때문에 PV (Photovoltaics) Cell의 anti-reflective coating에 적용 할 수 있다. 본 연구에서는 pulsed DC magnetron sputtering을 이용하여 Ga-doped ZnO (GZO) 박막을 증착하였고, HCl 0.5 wt %로 wet etching을 통하여 surface texturing을 진행하였다. 결정성은 X-ray diffractometer (XRD)로 분석하였으며, 표면 형상은 Scanning Electron Microscope (SEM)을 통해 확인하였다. Van der Pauw 방법을 통해 resistivity, carrier concentration, hall mobility 등의 전기적 특성을 분석하였고 UV-Vis spectrophotometer 를 통해 투과도 및 반사도를 측정하였다.

• Journal of the Korean Ceramic Society
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• v.54 no.6
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• pp.511-517
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• 2017

With different working pressures and substrate biases, Cr-Al-N coatings were deposited by hybrid physical vapor deposition (PVD) method, consisting of unbalanced magnetron (UBM) sputtering and arc ion plating (AIP) processes. Cr and Al targets were used for the arc ion plating and the sputtering process, respectively. Phase analysis, and composition, binding energy, and microstructural analyses were performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM), respectively. Surface droplet size of Cr-Al-N coatings was found to decrease with increasing substrate bias. A decrease of the deposition rate of Cr-Al-N films was expected due to the increase of substrate bias. The coatings were grown with textured CrN phase and (111), (200), and (220) planes. X-ray diffraction data show that all Cr-Al-N coatings shifted to lower diffraction angles due to the addition of Al. The XPS results were used to determine the $Cr_2N$, CrN, and (Cr,Al)N binding energies. The compositions of the Cr-Al-N films were measured by XPS to be Cr 23.2~36.9 at%, Al 30.1~40.3 at%, and N 31.3~38.6 at%.