• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.226-233
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• 2008

The nucleation and evolution process of Ge nano-islands on Si(001) surfaces grown by chemical vapor deposition have been explored using atomic force microscopy (AFM). The Ge nano-islands are grown by exposing the substrates to a mixture of gasses GeH4 and H2 at pressure of 0.1-0.5Torr and temperatures of $600-650^{\circ}C$. The effect of growth conditions such as temperature, Ge thickness, annealing time on the shape, size, number density, and surface distribution was investigated. For Ge deposition greater than ${\sim}5$ monolayer (ML) with a growth rate of ${\sim}0.1ML/sec$ at $600^{\circ}C$, we observed island nucleation on the surface indicating the transition from strained layer to island structure. Further deposition of Ge led to shape transition from initial pyramid and hut to dome and superdome structure. The lateral average size of the islands increased from ${\sim}20nm$ to ${\sim}310nm$ while the number density decreased from $4{\times}10^{18}$ to $5{\times}10^8cm^{-2}$ during the shape transition process. In contrast, for the samples grown at a relatively higher temperature of $650^{\circ}C$ the morphology of the islands showed that the dome shape is dominant over the pyramid shape. The further deposition of Ge led to transition from the dome to the superdome shape. The evolution of shape, size, and surface distribution is related to energy minimization of the islands and surface diffusion of Ge adatoms. In particular, we found that the initially nucleated islands did not grow through long-range interaction between whole islands on the surface but via local interaction between the neighbor islands by investigation of the inter-islands distance.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.67-73
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• 2015

This is a basic research for improving soft magnetic property of Fe based nano crystalline alloy powder core. The main study is done around characteristics of permeability, core loss, and DC bias depending on amount of insulation coating agent and particle size. First, $Fe_{73.5}Si_{13.5}B_9Nb_3Cu_1$ amorphous alloy ribbon was fabricated by using the planar flow casting (PFC) device. Then, heat treatment and ball milling were done to obtain alloy powder. The amount of polyether imide (PEI) added to it was varied by 0.5, 1.0, 2.0, 2.5 wt% to have compression molding into $16ton/cm^2$. After going through crystalline heat treatment, the made toroidal nano crystalline powder core ($OD12.7mm^*ID7.62mm^*H4.75mm$) had smaller permeability as amount of insulation coating agent decreases. However, it was found out that core loss and DC bias characteristics have been improved. The reason for this results were expected to be because green density of power core decreases as amorphous alloy powder particles become smaller as amount of alloy powder insulation coating agent increases, it was determined that 1 wt% of insulation coating agent is appropriate. Also, for powder core made based on alloy powder size with amount of insulation coating agent fixed at 1 wt%, effective permeability and core loss were outstanding as particle size became bigger. However, characteristics of DC bias became worse as applied DC field increases. This is expected to be due to insulation effect, residual pores, or molding density of powder core resulting from thickness of coating on surface of alloy powder.

• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.37-40
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• 2009

In this study, we made a high efficiency x-ray detecting sensor using the lead oxide(PbO) that are used in direct method of x-ray detector. PbO with nano size particles is produced by sol-gel method for high efficiency. The produced PbO with nano size is deposited on ITO(Induim Tin Oxide) glass in several temperature using the PIB(particle-in-binder) method. The thickness of the deposited PbO is about $200{\mu}m$. Through the measurement of dark current, sensitivity and SNR(Signal To Noise Ratio), an electrical properties of the produced PbO film are analyzed. Therefore, we show that an electrical properties are changed according to a temperature and that the PbO film that was treated at $500^{\circ}C$ in O2 atmosphere is the most high efficiency x-ray detecting sensor.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.157-157
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• 2015

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}g/m^2day$. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2day$) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study NBAS process was introduced to deposit enhanced film density single gas barrier layer with a low WVTR. Fig. 1. shows a schematic illustration of the NBAS apparatus. The NBAS process was used for the $Al_2O_3$ nano-crystal structure films deposition, as shown in Fig. 1. The NBAS system is based on the conventional RF magnetron sputtering and it has the electron cyclotron resonance (ECR) plasma source and metal reflector. $Ar^+$ ion in the ECR plasma can be accelerated into the plasma sheath between the plasma and metal reflector, which are then neutralized mainly by Auger neutralization. The neutral beam energy is controlled by the metal reflector bias. The controllable neutral beam energy can continuously change crystalline structures from an amorphous phase to nanocrystal phase of various grain sizes. The $Al_2O_3$ films can be high film density by controllable Auger neutral beam energy. we developed $Al_2O_3$ high dense barrier layer using NBAS process. We can verified that NBAS process effect can lead to formation of high density nano-crystal structure barrier layer. As a result, Fig. 2. shows that the NBAS processed $Al_2O_3$ high dense barrier layer shows excellent WVTR property as a under $2{\times}10^{-5}g/m^2day$ in the single barrier layer of 100nm thickness. Therefore, the NBAS processed $Al_2O_3$ high dense barrier layer is very suitable in the high efficiency OLED application.

• Polymer(Korea)
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• v.29 no.2
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• pp.146-150
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• 2005

A nano-stereolithouaphy (NSL) apparatus has been developed for fabrication of microstructures with the resolution of 150 nanometers. In the NSL process, a complicated 3D structure can be fabricated by building layer by layer, so it does not require any sacrificial layer or any supporting structure. A laminated layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) which was induced by a femtosecond laser. When the fabrication of a 3D laminated structure was finished, unsolidified liquid-stage resins were removed to develop the fabricated structure by dropping several droplets of solvent, then the polymerized structure was only left on the glass substrate. A microstructure is fabricated by vector scanning method to save the fabrication time. The shell thickness of a structure is very thin within 200 nm, when it is fabricated by a single contour scanning (SCS) path. So, a fabricated structure can be deformed easily in the developing process. In this work, a double contour scanning (DCS) method was proposed to reinforce the strength of a shell typed structure, and a microcup was fabricated to show the usefulness of the developed NSL system and the DCS method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.195-200
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• 2007

We fabricated thermally-evaporated 10 nm-Ni/70 w-Poly-Si/200 $nm-SiO_2/Si$ and $10nm-Ni_{0.5}Co_{0.5}/70$ nm-Poly-Si/200 $nm-SiO_2/Si$ structures to investigate the microstructure of nickel monosilicide at the elevated temperatures required fur annealing. Silicides underwent rapid anneal at the temperatures of $600{\sim}1100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process formed on top of the polycrystalline silicon substrate mimicking the gates. A four-point tester was used to investigate the sheet resistances. A transmission electron microscope and an Auger depth profile scope were employed for the determination of cross sectional microstructure and thickness. 20nm thick nickel cobalt composite silicides on polycrystalline silicon showed low resistance up to $900^{\circ}C$, while the conventional nickle silicide showed low resistance below $900^{\circ}C$. Through TEM analysis, we confirmed that the 70nm-thick nickel cobalt composite silicide showed a unique silicon-silicide mixing at the high silicidation temperature of $1000^{\circ}C$. We identified $Ni_3Si_2,\;CoSi_2$ phase at $700^{\circ}C$ using an X-ray diffractometer. Auger depth profile analysis also supports the presence of this mixed microstructure. Our result implies that our newly proposed NiCo composite silicide from NiCo alloy films process may widen the thermal process window for the salicide process and be suitable for nano-thick silicides.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.69-75
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• 2017

In this paper, slit ground resonator with slit and capacitor is proposed for practical use of magnetic resonant wireless power transfer(MR-WPT). And this paper presents the performance comparison of conventional loop resonator as Rx resonator to slit ground resonator. The proposed silt ground resonator with 31 cm width, 20.5 cm length, $35{\mu}m$ thickness is designed the crossing slit 1 cm width with only opened edge. And an external capacitors were connected at the opened edge of slit ground resonator for resonating at 6.78 MHz. The transfer efficiencies of MR-WPT were measured at open and short mode, and then the highest transfer efficiencies of MR-WPT according to the Rx resonators were plotted. In result, the transfer efficiency of MR-WPT with loop resonator was the highest. However, when the ground was inserted in receiver part at the bottom of laptop model, the transfer efficiency was closed 0 %. The transfer efficiency recovered the transfer efficiency of 67 % using slit ground resonator. The magnetic field was penetrated through the slit and proposed slit ground resonator works as resonator in MR-WPT.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.9-12
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• 2006

We have designed and fabricated micro power generators by electroplating which is important in MEMS(micro electro mechanical system) technique. We have electroplated MEMS coils on the glass substrates and have chosen one of these coils for experiments. The thickness, width, and length of the coil are $7{\mu}m,\;20{\mu}m$, and 1.6 m, respectively. We have analyzed the structure of MEMS coil by SEM. We have made a vibrating system for reproducible results in measurement. With reciprocating a magnet on the surface of a fabricated winding coil, the micro power generator produce an alternating voltage. We have changed the vibrational frequency from 0.5 Hz to 8 Hz. The generated voltage was 106 mV at 3 Hz and 198 mV at 6 Hz. We aim at the micro power generator which can change vibration energy to useful electric energy.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.162-162
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• 2017

AlCrN 코팅은 높은 경도, 낮은 표면 조도 등의 상온에서의 우수한 기계적 특성 이외에 고온에서 안정한 합금상의 형성으로 인하여 우수한 내열성을 보이는 코팅이며, Si을 첨가하여 나노복합구조를 갖는 AlCrSiN 코팅은 고경도 특성을 나타내는 나노결정립과 고내열성을 나타내는 $Si_3N_4$ 비정질이 동시에 존재함으로써 뛰어난 고온 특성까지 보유하여 공구 코팅으로의 적용 가능성이 크다. 본 연구에서는, 가혹화된 공구사용 환경 대응 하는 더욱 우수한 내마모성 및 내열성을 보이는 코팅막을 개발하기 위해 AlCrN/AlCrSiN 이중층 코팅을 합성하였다. 합성된 코팅의 구조 및 물성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, atomic force microscopy(AFM) 및 ball-on-disk wear tester를 사용하였다. 내열성을 확인하기 위하여 코팅을 furnace에 넣어 500, 600, 700, 800, 900도에서 30분 동안 annealing한 후에 nano-indentation을 사용하여 경도를 측정을 하였다. 5:5, 7:3, 9:1의 두께 비율로 AlCrN/AlCrSiN 이중층 코팅을 합성하였으며 모든 코팅의 두께는 $3{\mu}m$로 제어되었다. AlCrN 코팅층의 두께가 증가할수록, 이중층 코팅의 경도 및 내마모성은 점차 향상되었지만 코팅의 밀착력은 감소하였다. 일반적으로 AlCrN 코팅은 상대적으로 높은 잔류응력을 갖고 있으므로, AlCrN 층의 두께비율이 증가함에 따라 코팅내의 잔류응력이 높아져 코팅의 경도는 증가하고 밀착특성은 낮아진 것으로 판단된다. AlCrSiN 상부층 공정시 기판 바이어스 전압을 -50 ~ -200V 로 증가시키면서 이중층 코팅을 합성하였다. XRD 분석 결과, 공정 바이어스 전압이 증가함에 따라 AlCrSiN 상부층은 점차 비정질화 되었고, 코팅의 경도와 표면 특성이 향상되는 것을 확인하였다. 이러한 특성 향상은 높은 바이어스 인가가 이온 충돌효과의 증가를 야기시켰으, 이로 인해 치밀한 코팅층 합성에 의한 결과로 판단된다. AlCrN/AlCrSiN 이중층 코팅을 어닐링 한 후 경도 분석 결과, -150, -200V에서 합성한 코팅은 900도 이상에서 26GPa 이상의 높은 경도를 보인 것으로 보아 우수한 내열성을 갖는 것으로 확인 되었다. 이는 AlCrSiN 상부층의 높은 Si 함량 (11at.%) 으로 인한 충분한 $Si_3N_4$ 비정질상의 형성과, 고바이어스 인가로 인한 AlCrN 결정상과 $Si_3N_4$ 비정질상의 고른 분배가 코팅의 내열성을 향상시키는데 기여를 한 결과로 판단된다.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.87-92
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• 2003

$Ti_3AlC_2$was synthesized from TiCx and Al powder as a starting materials at the temperature range between$800^{circ}C;and;1500^{\circ}C$. The vacuum sintering and hot pressing methods were imployed to synthesize$Ti_3AlC_2$. The high purity$Ti_3AlC_2$was synthesized using TiCx and Al powder as starting materials without formation of Ti-Al intermetallic compound and Al-C compound.$Ti_2$AlC and$Ti_3AlC_2$were preferentially synthesized at$800^{\circ}C$and above$1200^{\circ}C$, respectively.$Ti_2$AlC formed at low temperature was transformed to$Ti_3AlC_2$by further reaction with TiC. In this study, the synthesis mechanism for$Ti_3AlC_2$was proposed. The synthesized$Ti_3AlC_2$showed the nano laminating structure consisting of$Ti_3AlC_2$crystal with the thickness of 45~120 nm.