• The Korean Journal of Ceramics
• /
• 제3권3호
• /
• pp.173-176
• /
• 1997

Direct metal ion beam deposition is considered to be a whole new thin film deposition technique. Unlike other conventional thin film deposition processes, the individual deposition particles carry its own ion beam energies which are directly coupled for the formation of this films. Due to the nature of ion beams, the energies can be controlled precisely and eventually can be tuned for optimizing the process. SKION's negative C- ion beam source is used to investigate the initial nucleation mechanism and growth. Strong C- ion beam energy dependence has been observed. Complete phase control of sp3 and sp3, control of the C/SiC/Si interface layer, control of crystalline and amorphous mode growth, and optimization of the physical properties for corresponding applications can be achieved.

• 한국세라믹학회지
• /
• 제28권1호
• /
• pp.1-10
• /
• 1991

Zirconium dioxide(ZrO2) thin films have been deposited by chemical vapor deposition technique involving the application of gas mixture of ZrCl4, and H2O into silicon wafers. The relationships between the deposition rate and various reaction parameters such as the deposition time, the gas flow rate, the deposition temperature, and the composition of reactant gases were studied. The film was identified as nearly stoichiometric monoclinic ZrO2. The apparent activation energy is about 19Kcal/mole at surface chemical reaction controlled region. The deposition rate is mainly influenced by the H2O-forming reacting between CO2 and H2.

• 한국재료학회지
• /
• 제21권12호
• /
• pp.666-672
• /
• 2011

The a-Si:H/c-Si hetero-junction (HJ) solar cells have a variety of advantages in efficiency and fabrication processes. It has already demonstrated about 23% in R&D scale and more than 20% in commercial production. In order to further reduce the fabrication cost of HJ solar cells, fabrication processes should be simplified more than conventional methods which accompany separate processes of front and rear sides of the cells. In this study, we propose a simultaneous deposition of intrinsic thin a-Si:H layers on both sides of a wafer by dual hot wire CVD (HWVCD). In this system, wafers are located between tantalum wires, and a-Si:H layers are simultaneously deposited on both sides of the wafer. By using this scheme, we can reduce the process steps and time and improve the efficiency of HJ solar cells by removing surface contamination of the wafers. We achieved about 16% efficiency in HJ solar cells incorporating intrinsic a-Si:H buffers by dual HWCVD and p/n layers by PECVD.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
• /
• pp.66.1-66.1
• /
• 2010

Microcrystalline silicon at low temperatures has been developed using plasma enhanced chemical vapor deposition (PECVD). It has been found that energetically positive ion and atomic hydrogen collision on to growing surface have important effects on increasing growth rate, and atomic hydrogen density is necessary for the increasing growth rate correspondingly, while keeping ion bombardment is less level. Since the plasma potential is determined by working pressure, the ion energy can be reduced by increasing the deposition pressure of 700-1200 Pa. Also, correlation of the growth rate and crystallinity with deposition parameters such as working pressure, hydrogen flow rate and input power were investigated. Consequently an efficiency of 7.9% was obtained at a high growth rate of 0.92 nm/s at a high RF power 300W using a plasma-enhanced chemical vapor deposition method (27.12MHz).

• 한국수소및신에너지학회논문집
• /
• 제14권1호
• /
• pp.8-16
• /
• 2003

$TiO_2$ thin films were deposited by DC reactive magnetron sputtering with variations in sputtering parameter such as Ar and $O_2$ flow rate, DC power, substrate temperature and magnetic field. Deposition rate, crystal structure, chemical bond of $TiO_2$ films on the deposition conditions were investigated by Alpha-step, X-ray Diffractometer(XRD), X-ray Photoelectron Spectroscopy(XPS). When the DC power was applied at 500watt, deposition rate of $TiO_2$ film was about 480A/min. $TiO_2$ films coated under the deposition condition of 15sccm Ar and 7~10sccm $O_2$ flow rate was only observed anatase phase. With increasing substrate temperature from RT to $300^{\circ}C$, crystal orientation of $TiO_2$ films variously became.

• 한국레이저가공학회지
• /
• 제18권3호
• /
• pp.1-5
• /
• 2015

A 3D printer based on laser powder deposition (LPD), also known as DED (direct energy deposition), has been developed for fabricating metal parts. The printer uses a ytterbium fiber laser (1070nm, 1kW) and is equipped with an Ar purge chamber, a three-dimensional translation stage and a powder feeding system composed of a powder chamber and delivery nozzles. To demonstrate the performance of the printer, a tapered cylinder of 320mm in height has been fabricated successfully using Ti-6Al-4V powders. The process parameters including the laser output power, the scan speed, and the powder feeding rate have been optimized. A 3D printed test specimen shows mechanical properties (yield strength, ultimate tensile strength, and elongation) exceeding the criteria to employed in a variety of Ti alloy applications.

• 한국재료학회지
• /
• 제30권12호
• /
• pp.660-665
• /
• 2020

Silicon heterojunction solar cells can achieve high conversion efficiency with a simple structure. In this study, we investigate the passivation characteristics of VOx thin films as a hole-selective contact layer using ALD (atomic layer deposition). Passivation characteristics improve with iVoc (implied open-circuit voltage) of 662 mV and minority carrier lifetime of 73.9 µs after post-deposition annealing (PDA) at 100 ℃. The improved values are mainly attributed to a decrease in carbon during the VOx thin film process after PDA. However, once it is annealed at temperatures above 250 ℃ the properties are rapidly degraded. X-ray photoelectron spectroscopy is used to analyze the chemical states of the VOx thin film. As the annealing temperature increases, it shows more formation of SiOx at the interface increases. The ratio of V5+ to V4+, which is the oxidation states of vanadium oxide thin films, are 6:4 for both as-deposition and annealing at 100 ℃, and 5:5 for annealing at 300 ℃. The lower the carbon content of the ALD VOx film and the higher the V5+ ratio, the better the passivation characteristics.

• 한국분말재료학회지
• /
• 제29권1호
• /
• pp.56-62
• /
• 2022

Atomic layer deposition (ALD) is a promising technology for the uniform deposition of thin films. ALD is based on a self-limiting mechanism, which can effectively deposit thin films on the surfaces of powders of various sizes. Numerous studies are underway to improve the performance of thermoelectric materials by forming core-shell structures in which various materials are deposited on the powder surface using ALD. Thermoelectric materials are especially relevant as clean energy storage materials due to their ability to interconvert between thermal and electrical energy by the Seebeck and Peltier effects. Herein, we introduce a surface and interface modification strategy based on ALD to control the performance of thermoelectric materials. We also discuss the properties of the interface between various deposition materials and thermoelectric materials.

• Journal of Radiation Protection and Research
• /
• 제40권4호
• /
• pp.231-243
• /
• 2015

Four different paddy soils collected around the Gyeongju nuclear site were treated with $^{99}TcO_4{^-}$ solution under the assumption of two contrasting contamination scenarios. Scenario I (SN-I) is for a pre-transplanting deposition of $^{99}Tc$ followed by plowing, whereas SN-II is for its deposition onto the water surface shortly after transplanting. Rice plants were grown in lysimeters in a greenhouse. Plant uptake of $^{99}Tc$ was quantified with the $TF_{area}$ ($m^2{\cdot}kg^{-1}-dry$). The SN-II $TF_{area}$ values for straws and brown rice, having been generally higher than the SN-I values, were within the ranges of $6.9{\times}10^{-3}{\sim}4.1{\times}10^{-2}$ and $5.2{\times}10^{-6}{\sim}7.3{\times}10^{-5}$, respectively. Sorption onto clay seems to have decreased $^{99}Tc$ uptake in SN-I, whereas it may have had an insignificant effect in SN-II. A phenomenon characteristic of submerged paddy soil, i.e., the development of a thin oxic surface layer may have greatly affected the rice uptake of SN-II $^{99}Tc$. The surface-water concentrations of $^{99}Tc$ were much higher in SN-II than in SN-I. For the percolating water, however, the opposite was generally true. At most 1.3% of the applied $^{99}Tc$ were leached through such percolation. The use of empirical deposition time-dependent $TF_{area}$ values was considered desirable in assessing the radiological impact of a growing-season deposition of $^{99}Tc$ onto paddy fields.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
• /
• pp.381-384
• /
• 2011

본 연구에서는 초음속 비행체의 조파저항을 감소시키기 위하여, 최대 주파수 80 kHz의 반복 레이저 펄스에 의해 야기된 에너지 부가법에 관한 실험적 연구가 수행된다. 기류 마하수 1.94의 흡입식 초음속 풍동의 바깥에 설치된 초점렌즈에 의하여 레이저 펄스가 실린더 모델 전단부에 집약된다. 시간변동 항력과 정체압력은 로드셀과 PCB 압력센서에 의해서 측정되며, 동시에 고속 카메라를 이용하여 가시화가 수행된다. 본 연구의 결과로부터, 레이저 펄스 에너지 부가에 의한 항력 저감량은 레이저 펄스 주파수가 증가할 때, 최대 21%까지 거의 선형적으로 증가하였다. 부가 에너지 효율은 레이저 펄스 에너지에만 의존하는 결과를 얻었으며, 최대 1000%까지 달성되었다.