• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.355-360
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• 2002

ElectroSlag Strip Overlaying (ESSO) process has been around since 1970. ESSO process had limited acceptance due to a few problems associated with the use of this process in its very early stage. Limited knowledge and, most significantly, poor quality of the equipment and welding flux gave the ESSO process a bad name. However, this process is well accepted today and used in North America, Europe and Japan. The ESSO process provides low dilution overlays at high deposition rates, excellent and consistent deposit chemistry with excellent surface quality, and virtually no defects. Capitan has taken this process one step further through extensive research and development of the process itself as well as the equipment. The improvement brought to the process warranted the issuance in May 2000 of an US patent. This study demonstrates the feasibility of this process with immediate positive production results. The main achievements of this work are as follows: $\textbullet$ Development of six various strip-flux combinations on three different base materials: carbon steel, $\frac{1}{4}$ Cr/.5 Mo and 2 $\frac{1}{4}$ Cr/l Mo, fully tested with: penetrant, ultrasound, bends, hardness, overlay chemistry, corrosion and hydrogen disbonding. $\textbullet$ 12" dia. 90 hot formed elbows from straight pipe electroslag overlayed with "1 layer" and "2 layer" Alloy 625 $\textbullet$ a very unique development of miniaturized overlaying equipment able to perform overlay in pipe with diameters as low as 10" (254 mm). This development has large applications in the field of offshore, petrochemical, refining, pulp and paper and power generation industries. The aftermath of this development was its immediate acceptance by major end users with the completion of four projects of overlayed pipe in the USA and Far East Asia.

• 한국세라믹학회지
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• 제40권6호
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• pp.589-593
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• 2003

실리카 평판광회로는 다양한 광수동소자에 응용이 되고 있으며, 이를 구성하는 SiO$_2$와 GeO$_2$-SiO$_2$ 막은 화염가수분해증착에 의해 증착되었다. SiO$_2$ 막은 산-수소 토치에 SiCl$_4$, POC1$_3$와 BCl$_3$를 주입하여 화염가수반응에 의해 생성되었으며, POC1$_3$/BC1$_3$ 유량비가 증가함에 따라 P 농도는 2.0-2.8 at%까지 증가하였고, 굴절률은 1.4584-1.4605로 증가하였다. GeO$_2$-SiO$_2$ 막의 굴절률은 GeCl$_4$ 유량에 의해 제어되었으며 30-120 sccm으로 증가함에 따라 1.4615-1.4809로 증가하였다.

• 융합정보논문지
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• 제10권6호
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• pp.28-34
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• 2020

본 논문에서는 VCSEL (Vertical Cavity Surface Emitting Laser) 레이저를 만드는 구조와 유사한 GaAs 웨이퍼상에 MOCVD (Metal Organic Chemical Vapor Deposition) 장비로 GaAs와 AlGaAs 에피층을 형성시킨 구조를 사용한다. 3차원 공진현상에 의해 자연 발생되는 광양자테 (PQR: Photonic Quantum Ring) 소자를 건식 식각 방법인 CAIBE (Chemically Assisted Ion Beam Etching) 기술로 제작하였지만, 진공 분위기에서 진행해야 하는 문제점 때문에 저가격으로 쉽게 소자를 제작할 수 있는 방법이 연구되었고, 그 결과 인산, 과산화수소, 메탄올이 혼합된 용액의 습식식각 기술로 가능성을 확인하였으며, 이 방법을 적용하여 소자를 제작한 내용에 대해 논한다. 또한, 제작된 광소자의 스펙트럼을 측정하였고, 이 결과들을 이론적으로 해석하여 얻은 파장값과 비교한다. 광양자테 소자는 3차원 형상으로 세포를 모델링하거나, 디스플레이 분야로의 응용이 가능할 것으로 기대한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.380.2-380.2
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• 2014

Direct synthesis of graphene using a chemical vapor deposition (CVD) has been considered a facile way to produce large-area and uniform graphene film, which is an accessible method from an application standpoint. Hence, their fundamental understanding is highly required. Unfortunately, the CVD growth mechanism of graphene on Cu remains elusive and controversial. Here, we present the effect of graphene growth parameters on the number of graphene layers were systematically studied and growth mechanism on copper substrate was proposed. Parameters that could affect the thickness of graphene growth include the pressure in the system, gas flow rate, growth pressure, growth temperature, and cooling rate. We hypothesis that the partial pressure of both the carbon sources and hydrogen gas in the growth process, which is set by the total pressure and the mole fraction of the feedstock, could be the factor that controls the thickness of the graphene. The graphene on Cu was grown by the diffusion and precipitation mode not by the surface adsorption mode, because similar results were observed in graphene/Ni system. The carbon-diffused Cu layer was also observed after graphene growth under high CH4 pressure. Our findings may facilitate both the large-area synthesis of well-controlled graphene features and wide range of applications of graphene.

• 한국진공학회지
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• 제7권1호
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• pp.29-34
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• 1998

PECVD방법으로 증착된 비정질 실리콘(a-Si)박막이 고상결정화되고 x-선 회절 (XRD)방법으로 조사되었다. a-Si박막들은 기판 온도 120-$380^{\circ}C$사이에서 Si(100)웨이퍼 위에 $SiH_4$가스 혹은 수소희석된 $SiH_4$가스로 증착되고, $600^{\circ}C$로 가열되어 결정화되었다. 고상화 되었을 때(111), (220), (311)XRD피크들이 나타났고 (111) 우선방위가 두드러졌다. 고상결정 화된 다결정 실리콘(poly-Si)박막들의 XRD피크의 세기는 기판온도가 낮아짐에 따라 증가되 었고, 수소희석은 고상화 효과를 감소시켰다. XRD로 측정된(111)결정립의 평균크기는 기판 온도가 낮아짐에 따라 약 10nm로 증가하였다. 기판온도가 낮아질수록 증착속도는 증가하였 으며, 결정의 크기는 증착속도와 밀접한 관계가 있었다. Si계의 구조적 무질서도가 클수록 고상화에 의한 결정립의 크기도 커지는 것으로 생각된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.53-53
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• 2011

As the dimension of Cu interconnects has continued to reduce, its resistivity is expected to increase at the nanoscale due to increased surface and grain boundary scattering of electrons. To suppress increase of the resistivity in nanoscale interconnects, alloying Cu with other metal elements such as Al, Mn, and Ag is being considered to increase the mean free path of the drifting electrons. The formation of Al alloy with a slight amount of Cu broadly studied in the past. The study of Cu alloy including a very small Al fraction, by contrast, recently began. The formation of Cu-Al alloy is limited in wet chemical bath and was mainly conducted for fundamental studies by sputtering or evaporation system. However, these deposition methods have a limitation in production environment due to poor step coverage in nanoscale Cu metallization. In this work, gap-filling of Cu-Al alloy was conducted by cyclic MOCVD (metal organic chemical vapor deposition), followed by thermal annealing for alloying, which prevented an unwanted chemical reaction between Cu and Al precursors. To achieve filling the Cu-Al alloy into sub-100nm trench without overhang and void formation, furthermore, hydrogen plasma pretreatment of the trench pattern with Ru barrier layer was conducted in order to suppress of Cu nucleation and growth near the entrance area of the nano-scale trench by minimizing adsorption of metal precursors. As a result, superconformal gap-fill of Cu-Al alloy could be achieved successfully in the high aspect ration nanoscale trenches. Examined morphology, microstructure, chemical composition, and electrical properties of superfilled Cu-Al alloy will be discussed in detail.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.88.1-88.1
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• 2012

Silicon nanowires (SiNWs), due to their unusual quantum-confinement effects that lead to superior electrical and optical properties compared to those of the bulk silicon, have been widely researched as a potential building block in a variety of novel electronic devices. The conventional means for the synthesis of SiNWs has been the vapor-liquid-solid method using chemical vapor deposition; however, this method is time consuming, environmentally unfriendly, and do not support vertical growth. As an alternate, the electroless etching method has been proposed, which uses metal catalysts contained in aqueous hydrofluoric acids (HF) for vertically etching the bulk silicon substrate. This new method can support large-area growth in a short time, and vertically aligned SiNWs with high aspect ratio can be readily synthesized with excellent reproducibility. Nonetheless, there still are rooms for improvement such as the poor surface characteristics that lead to degradation in electrical performance, and non-uniformity of the diameter and shapes of the synthesized SiNWs. Here, we report a facile method of SiNWs synthesis having uniform sizes, diameters, and shapes, which may be other than just cylindrical shapes using a modified nanosphere lithography technique. The diameters of the polystyrene nanospheres can be adjustable through varying the time of O2 plasma treatment, which serve as a mask template for metal deposition on a silicon substrate. After the removal of the nanospheres, SiNWs having the exact same shape as the mask are synthesized using wet etching technique in a solution of HF, hydrogen peroxide, and deionized water. Different electrical and optical characteristics were obtained according to the shapes and sizes of the SiNWs, which implies that they can serve specific purposes according to their types.

• 공업화학
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• 제31권5호
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• pp.581-584
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• 2020

The effect of a chemical pretreatment on the surface carbon was investigated using a scanning electron microscope (SEM) and electrochemical methods. Primitive carbon has a reducing power likely due to incompletely oxidized functional groups on the surface. We aim to control this reducing power by chemical treatment and apply for the spontaneous deposition of nanoparticles (NPs). Highly ordered pyrolytic graphite (HOPG) was initially treated with a reducing agent, NaBH4 or an oxidizing agent, KMnO₄, for 5 min. Subsequently, the pretreated carbon was immersed in a platinum (Pt) precursor. Unexpectedly, SEM images showed that the reducing agent increased spontaneous PtNPs deposition while the oxidizing agent decreased Pt loading more as compared to that of using bare carbon. However, the amount of Pt on the carbon obviously decreased by NaBH₄ treatment for 50 min. Secondly, spontaneous reduction on pretreated glassy carbon (GC) was investigated using the catalytic hydrogen evolution reaction (HER). GC electrode treated with NaBH4 for a short and long time showed small (onset potential: -640 mV vs. MSE) and large overpotential for the HER, respectively. Although the mechanism is unclear, the electrochemistry results correspond to the optical data. As a proof-of-concept, these results demonstrate that chemical treatments can be used to design the shapes and amounts of deposited catalytic metal on carbon by controlling the surface state.

• 한국표면공학회지
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• 제36권5호
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• pp.357-363
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• 2003

The aim of this work is the synthesis of a-C:H films from methane gas using surface spark discharge at the atmospheric pressure. Properties of these films have been investigated as functions of energy W delivered per a methane molecule in the discharge. The method enables the coatings to be deposited with high growth rates (up to $100 \mu\textrm{m}$/hour) onto large-area substrates. It is shown that the films consist of spherical granules with diameter of 20∼50 nm formed in the spark channel and then deposited onto the substrate. The best film characteristics such as minimum hydrogen-to-carbon atoms ratio H/C=0.69, maximum hardness $H_{v}$ =3 ㎬, the most dense packing of the granules and highest scratch resistance has been obtained under the condition of highest energy W of 40 eV. The deposited a-C:H coatings were found to be more soft and hydrogenated compared to the diamond-like hydrogenated (a-C:H) films which obtained by traditional plasmaenhanced chemical vapor deposition methods at low pressure (＜10 Torr). Nevertheless, these coatings can be potentially used for scratch protection of soft plastic materials since they are of an order harder than plastics but still transparent (the absorption coefficient is about $10^4$∼$10^{5}$ $m^{-1}$ At the same time the proposed method for fast deposition of a-C:H films makes this process less expensive compared to the conventional techniques. This advantage can widen the application field of. these films substantially.y.

• 한국재료학회지
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• 제23권7호
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• pp.359-365
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• 2013

We investigated the nanostructural, chemical and optical properties of nc-Si:H films according to deposition conditions. Plasma enhanced chemical vapor deposition(PECVD) techniques were used to produce nc-Si:H thin films. The hydrogen dilution ratio in the precursors, [$SiH_4/H_2$], was fixed at 0.03; the substrate temperature was varied from room temperature to $600^{\circ}C$. By raising the substrates temperature up to $400^{\circ}C$, the nanocrystalite size was increased from ~2 to ~7 nm and the Si crystal volume fraction was varied from ~9 to ~45% to reach their maximum values. In high-resolution transmission electron microscopy(HRTEM) images, Si nanocrystallites were observed and the crystallite size appeared to correspond to the crystal size values obtained by X-ray diffraction(XRD) and Raman Spectroscopy. The intensity of high-resolution electron energy loss spectroscopy(EELS) peaks at ~99.9 eV(Si $L_{2,3}$ edge) was sensitively varied depending on the formation of Si nanocrystallites in the films. With increasing substrate temperatures, from room temperature to $600^{\circ}C$, the optical band gap of the nc-Si:H films was decreased from 2.4 to 1.9 eV, and the relative fraction of Si-H bonds in the films was increased from 19.9 to 32.9%. The variation in the nanostructural as well as chemical features of the films with substrate temperature appears to be well related to the results of the differential scanning calorimeter measurements, in which heat-absorption started at a substrate temperature of $180^{\circ}C$ and the maximum peak was observed at ${\sim}370^{\circ}C$.