• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.230-230
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• 2010

유기물 반도체 화합물인 Cu-Pc(copper(II)-phthalocyanine)는 우수한 전기적 광학적 특성을 가지며, OLED, MISFET등 소자로서의 활용도가 높다. Cu-Pc 화합물은 $\alpha$-phase, $\beta$-phase, $\gamma$-phase를 포함하는 여러 가지 다결정 polymer로 존재할 수 있다. 가장 잘 알려진 구조로는 열적으로 준안정적인 $\alpha$-phase와 열적으로 안정적인 $\beta$-phase가 있다. Cu-Pc 박막의 구조 및 흡수 특성과 전기적 특성에 대한 기술이 확실히 규명되지 않아 본 연구에서는 두께와 열처리 조건에 따른 결정성 및 방향성을 조사하기 위하여 $\alpha$-phase와 $\beta$-phase의 phase transition 현상 및 전기적 광학적 특성을 규명 하고자 한다. 진공증착 방법 중 하나인 PVD 방법의 thermal evaporation deposition을 이용하여 glass, ITO 기판위에 두께와 열처리에 따른 전기적?광학적 특성을 연구하였다. Cu-Pc 박막의 성장두께는 5nm~50nm 이내로 fluxmeter 및 thickness monitor를 이용하여 제어하였다. 5nm~50nm의 두께에 따른 기판온도를 $200^{\circ}C$로 고정하여 전열 처리 및 후열 처리하여 온도에 따른 박막을 성장한 후, 결정 구조 및 특성 변화와 phase transition 분석하였다. 제작된 Cu-Pc의 박막은 $\alpha$-phase와 $\beta$-phase로 구분할 수 있으며, 열처리에 따른 phase transition 현상이 뚜렷함을 알 수 있다. XRD(X-ray diffraction)를 통하여 박막에 대한 결정 구조 분석 및 FE-SEM(field emission scanning electron microscopy)와 AFM(atomic force microscopy)을 이용하여 Cu-Pc 박막의 구조적 결정성과 방향성 등, 표면 상태와 형상구조에 대해 표면의 특성을 측정하며, 광 흡수도(UV-visible absorption spectra)을 이용하여 phase transition 현상에 따른 I-V 특성을 비교분석 하였다.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.259-265
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• 2009

We fabricated the field effect transistor using single crystalline ZnO nanowires synthesized by a conventional thermal evaporation method and investigated their basic properties under the various conditions such as ultraviolet irradiation, reducing gas and electrolyte. The typical carrier concentration and mobility of the single crystalline ZnO nanowire with a diameter of 100 nm and length of 5 um were $1.30{\times}10^{18}cm^{-3}$ and $15.6cm^2V^{-1}s^{-1}$, respectively. The current of ZnO nanowire under ultraviolet irradiation significantly increased about 400 times higher as compared to in the darkness. In addition, the ZnO nanowire showed typical sensing characteristics for $H_2$ and CO due to well-known surface reactions and typical current-voltage characteristics under the 0.1 M NaCl electrolyte.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.229.2-229.2
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• 2013

Yttrium oxide (Y2O3)는 band gap이 5.5 eV 정도로 상대적으로 넓고, 굴절상수가 1.8, 유전율이 10~15, Silicon 과의 격자 불일치가 작은 특성을 가지고 있다. 또한 녹는점이 높아 열적으로 안정하기 때문에 전자소자 및 광학소자에 다양하게 응용되는 물질이다. Y2O3 박막은 다양한 방법으로 증착할 수 있는데, 그 방법에는 e-beam evaporation, laser ablation, sputtering, thermal oxidation, metal-organic chemical vapor deposition, and atomic layer deposition (ALD) 등이 있다. ALD는 기판 표면에 흡착된 원자들의 자기 제한적 반응에 의하여 박막이 증착되기 때문에 박막 두께조절이 용이하고 step coverage와 uniformity 측면에서 큰 장점이 있다. 이전에는 Y(thd)3 and Y(CH3Cp)3 와 같은 금속 전구체를 이용하여 ALD를 진행하여, 증착 속도가 낮고 defect이 많아 non-stoichiometric한 조성의 박막이 증착되는 문제점이 있었다. 이번 연구에서는, (iPrCp)2Y(iPr-amd)와 탈이온수를 사용하여 Y2O3 박막을 증착하였다. Y2O3 박막 증착에 사용한 Y 전구체는 상온에서 액체이고 $192^{\circ}C$ 에서 1 Torr의 높은 증기압을 갖는다. Y2O3 박막 증착을 위하여 Y 전구체는 $150^{\circ}C$ 로 가열하여 N2 gas를 이용하여 bubbling 방식으로 공정 챔버 내로 공급하였다. Y2O3 박막의 ALD window는 $250{\sim}350^{\circ}C$ 였으며, Y 전구체의 공급시간이 5초에 다다르자 더 이상 증착 두께가 증가하지 않는 자기 제한적 반응을 확인할 수 있었다. 그리고 증착된 Y2O3 박막의 특성 분석을 위해 Atomic force microscopy (AFM)과 X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) 를 진행하였다. 박막의 Surface morphology 는 매끄럽고 uniform 하였으며, 특히 고체 금속 전구체를 사용했을 때와 비교하여 수산화물이 거의 없는 박막을 얻을 수 있었다. 그리고 조성 분석을 통해 증착된 Y2O3 박막이 stoichiometric하다는 것을 알수 있었다. 또한 metal-insulator-metal (MIM) 구조 (Ru/Y2O3/Ru) 의 resistor 소자를 형성하여 저항 스위칭 특성을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.254-254
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• 2010

Cu-Pc(copper(II)-phthalocyanine)는 박막의 형성과정에서 열처리 방식과 온도에 따라 박막의 구조가 변하며, 구조로는 열적으로 준 안정적인 $\alpha$-phase와 열적으로 안정적인 $\beta$-phase가 있다. 본 연구에서는 Cu-Pc 박막의 열적으로 안정적인 $\beta$-phase 구조에 대해 온도 조건 변화에 따른 표면 결정 성장의 특성을 연구하고자 한다. 진공증착 방법 중 하나인 thermal evaporation deposition을 이용하여 glass 기판위에 전열 처리 및 후열 처리에 대해 온도 조건 변화에 따른 $\beta$-phase type의 표면 결정 특성을 연구하였다. Cu-Pc 박막의 성장두께는 50nm 일정한 두께로 fluxmeter 및 thickness monitor를 이용하여 제어하였다. 50nm의 두께에 따른 기판온도를 $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$로 전열 처리한 후 각각 전열 처리한 기판온도에 대해 1hour, 2hour, 3hour 후열 처리하여 온도 조건에 따른 박막을 성장한 후, $\beta$-phase type에 대한 결정 구조 및 표면 특성 변화를 분석하였다. 제작된 Cu-Pc의 박막은 $\beta$-phase type으로, 열처리에 따른 $\beta$-phase transition 현상을 연구하였다. XRD(X-ray diffraction)를 통하여 박막에 대한 결정 구조 분석 및 FE-SEM(field emission scanning electron microscopy)을 이용하여 Cu-Pc 박막의 구조적 결정성과 방향성 등, 표면 상태와 형상구조에 대해 표면의 특성을 분석하며, 광 흡수도(UV-visible absorption spectra)을 이용하여 온도 조건에 따른 투과/흡수 현상을 비교분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.130.2-130.2
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• 2013

Today, chemical vapor deposition (CVD) of hydrocarbon gases has been demonstrated as an attractive method to synthesize large-area graphene layers. However, special care should be taken to precisely control the resulting graphene layers in CVD due to its sensitivity to various process parameters. Therefore, a facile synthesis to grow graphene layers with high controllability will have great advantages for scalable practical applications. In order to simplify and create efficiency in graphene synthesis, the graphene growth by thermal annealing process has been discussed by several groups. However, the study on growth mechanism and the detailed structural and optoelectronic properties in the resulting graphene films have not been reported yet, which will be of particular interest to explore for the practical application of graphene. In this study, we report the growth of few-layer, large-area graphene films using rapid thermal annealing (RTA) without the use of intentional carbon-containing precursor. The instability of nickel films in air facilitates the spontaneous formation of ultrathin (<2~3 nm) carbon- and oxygen-containing compounds on a nickel surface and high-temperature annealing of the nickel samples results in the formation of few-layer graphene films with high crystallinity. From annealing temperature and ambient studies during RTA, it was found that the evaporation of oxygen atoms from the surface is the dominant factor affecting the formation of graphene films. The thickness of the graphene layers is strongly dependent on the RTA temperature and time and the resulting films have a limited thickness less than 2 nm even for an extended RTA time. The transferred films have a low sheet resistance of ~380 ${\Omega}/sq$, with ~93% optical transparency. This simple and potentially inexpensive method of synthesizing novel 2-dimensional carbon films offers a wide choice of graphene films for various potential applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.440-443
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• 2002

Present1y the X-Ray diagnosis system is a real condition that is changing by digital ways in it's existent analog ways. This digital radiation detector is divided by the direct method and the indirect method. The indirect method of applied voltage has special qualities that the resolution is low than direct method by diffusion effect that happens. The conversion process ( radiation${\rightarrow}$visible ray${\rightarrow}$electrical signal of two times, has shortcomings that the energy conversion efficiency of electrical signal is low. The direct method has shortcomings that need strong electric fie1d to detect electrical signal efficiently. This research achieved to develop digital detector of the Hybrid method that have form that mixes two ways to supplement shortcoming of direct. indirect method. A studied electrical characteristic by Iodine's Mixture ratio change is added to selenium in the detector which has a multi-layer structure (Oxybromide + a-Se). There are 8 kinds of Manufactured compositions to amorphous selenium Iodine each 30ppm, 100ppm, 200 ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm by a doped photoconductor through a vacuum thermal evaporation method. The phosphor layer is consisted of Oxybromide ($BrO_2$) which uses optical adhesives multi-layer structure. The manufactured compositions calculates and compares Net Charge and signal to noise ratio measuring Photocurrent about Darkcurrent and X-ray. When doped Iodine Mixture ratio is 500ppm to the multi-layer structure (Oxybromide + a-Se), applied voltage of $3V/{\mu}m$, leakage current of compositions $2.61nA/cm^2$ and net charge value by 764pC/$cm^2$/mR then the best result appeared.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.230-234
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• 2009

It is significant technique to increase competitiveness that solar cells have a high energy conversion efficiency and cost effectiveness. When making high efficiency crystalline Si solar cells, evaporated Ti/Pd/Ag contact system is widely used in order to reduce the electrical resistance of the contact fingers. However, the evaporation process is no applicable to mass production because high vacuum is needed. Furthermore, those metals are too expensive to be applied for terrestrial applications. Ni/Cu/Ag contact system of silicon solar cells offers a relatively inexpensive method of making electrical contact. Ni silicide formation is one of the indispensable techniques for Ni/Cu/Ag contact sytem. Ni was electroless plated on the front grid pattern, After Ni electroless plating, the cells were annealed by RTP(Rapid Thermal Process). Ni silicide(NiSi) has certain advantages over Ti silicide($TiSi_2$), lower temperature anneal, one step anneal, low resistivity, low silicon consumption, low film stress, absence of reaction between the annealing ambient. Ni/Cu/Ag metallization scheme is an important process in the direction of cost reduction for solar cells of high efficiency. In this article we shall report an investigation of rapid thermal silicidation of nickel on silngle crystalline silicon wafers in the annealing range of $350-390^{\circ}C$. The samples annealed at temperatures from 350 to $390^{\circ}C$ have been analyzed by SEM(Scanning Electron Microscopy).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.381-387
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• 2008

The presence of non-condensable gases as an additional thermal resistance inside a refrigerating circuit has been found for a general refrigerator, The effect of non-condensable gases was varied by controlling the injection amount of dry air into the refrigerating circuit to increase a thermal resistance. Energy consumption tests for the refrigerator were conducted under the various amounts of non-condensable gases. The tested refrigerating circuit was the household refrigerator. As the molar fraction of non-condensable gases was increased from 0% to 1.46%, the amount of energy consumption was found to increase up to 25%. The increase of the amount of non-condensable gases in refrigerating circuit was found to result in increasing the condensation temperature at the condenser and decreasing the evaporation temperature at the evaporator, which were presumably caused by the low specific heat and increased partial pressure of non-condensable gas.

• Journal of the Korean Society of Radiology
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• v.4 no.4
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• pp.37-40
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• 2010

In this paper, transport properties of charge carrier which is produced by x-ray exposure were investigated.. It is the research of charge transport and specific property of trap that is performed in direct digital x-ray image receptor. We measured transit time and drift mobility of charge carriers of a-Se photoconductor using time-of-flight method. We made a testing glass with a-Se of $100{\mu}m$ thickness on corning glass using thermal evaporation method. As a result of this experiment, electron and hole transit time was each $229.17{\mu}s$ and $8.73{\mu}s$ at $10V/{\mu}m$ electric field and drift mobility was each $0.00174cm^2/V{\cdot}s$, $0.04584cm^2/V{\cdot}s$. But the results shows us different measurement value of electron and charge drift mobility and it was investigated about charge transport properties and trap mechanism.

• Journal of the Korean Vacuum Society
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• v.21 no.4
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• pp.205-211
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• 2012

We investigated the optical and hydrophobic properties of the deposited silver (Ag) zinc oxide (ZnO) nanorods (NRs) on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates (i.e., ITO/PET). The ZnO NRs were grown by an electrochemical deposition using a sputtered ZnO seed layer and the Ag was deposited by using a thermal evaporator. For comparison, the same fabrication process was carried out on the bare ITO/PET without ZnO NRAs. Due to the discrete surface of ZnO NRs, the deposited Ag was formed as nano-scale particles, while the Ag became film-like for bare ITO/PET. In order to control the size and amount of Ag particles, the Ag deposition time was changed from 100 to 600 s. When the deposition time was increased, the Ag particles became larger and denser, and the absorptance was increased. This enhanced absorptance may be due to the localized surface plasmon resonance of Ag particles. Furthermore, the relatively high hydrophobicity was observed for the deposited Ag on the ZnO NRs/ITO/PET. These improved optical and surface properties are expected to be useful for flexible photovoltaic and optoelectronic devices.