• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1563-1565
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• 1997

Electroluminescence(EL)devices based on organic thin layers have attracted lot of interests because of their possible application as large-area light-emitting display. One of the problems of such devices is lifetime of the cell, where the degradation of the cell is partially due to the crystalliyzation of organic layers. In large part, this problem can be solved by using a multilayer device structure prepared by vapor deposition technique. In this study, blue lightemitting multilayer organic electroluminescence devices were fabricated using Poly (9-vinyl-carbazole) (PVK) and 2-(4'-tert-butylpheny])-5-(4"-bis-phenyl)1,3,4-oxadiazole (PBD) as hole trasport and electron transport material, respectively, where tris(8-hydroxyquinolinate) aluminum (Alq3) was used as a luminescenct material. A cell structure of glass substrate/indume-tin-oxide(ITO)/PVK/$Alq_3$/PBD/Mg:In was employed.

• 융합정보논문지
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• 제8권5호
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• pp.95-100
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• 2018

금속 산화물/그래핀 형태의 복합 나노소재는 높은 전기용량을 갖는 2차 전지의 전극용 소재 또는 고감도 가스 센서의 감지물질 등으로 활용되는 매우 유용한 기능성 소재이다. 본 논문에서는 열 화학기상증착(CVD, Chemical Vapor Deposition)으로 Cu Foil 위에 대면적으로 합성된 CVD 그래핀 및 고정렬 열분해 흑연(HOPG, Highly Oriented Pyrolytic Graphite)으로부터 기계적으로 박리된 그래핀 기판 위에 이산화바나듐($VO_2$) 나노구조물을 기상수송방법으로 직접 성장시키는 연구를 수행하였다. 연구결과 CVD 그래핀 기판의 경우, 그래핀 결정 경계에서 상대적으로 많이 존재하는 기능기들이 $VO_2$ 나노구조물에서 핵형성의 씨앗으로 작용하는 것이 확인되었다. 반면에 HOPG에서 기계적으로 박리된 그래핀 나노시트 표면에는 기능기가 균일하게 분포하기 때문에, 2차원과 3차원 형태로 $VO_2$ 나노구조물이 성장되었다. 이러한 연구결과는 고기능성 $VO_2$/그래핀 나노복합소재를 이용하여 높은 전기용량을 갖는 2차 전지 전극소재 및 고감도 가스 센서의 감지물질 합성에 유용하게 활용될 것으로 전망된다.

• 대한금속재료학회지
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• 제49권10호
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• pp.818-822
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• 2011

ZnO nanorods were grown on Au-coated Si substrates by vapor phase transport (VPT) at the growth temperature of $600^{\circ}C$ using a mixture of zinc oxide and graphite powders as source material. Au thin films with the thickness of 5 nm were deposited by ion sputtering. Temperature-dependent photoluminescence (PL) was carried out to investigate the optical properties of the ZnO nanorods. Five peaks at 3.363, 3.327, 3.296, 3.228, and 3.143 eV, corresponding to the free exciton (FX), neutral donor bound exciton ($D^{\circ}X$), first order longitudinal optical phonon replica of free exciton (FX-1LO), FX-2LO, and FX-3LO emissions, were obtained at low-temperature (10 K). The intensity of these peaks decreased and their position was red shifted with the increase in the temperature. The FX emission peak energy of the ZnO nanorods exhibited an anomalous behavior (red-blue-red shift) with the increase in temperature. This is also known as an "S-shaped" emission shift. The thermal activation energy for the exciton with increasing temperature in the ZnO nanorods is found to be about 26.6 meV; the values of Varshni's empirical equation fitting parameters are = $5{\times}10^{-4}eV/K$, ${\beta}=350K$, and $E_g(0)=3.364eV$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.375-375
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• 2010

CdTe as an absorber material is widely used in thin film solar cells with the heterostructure due to its almost ideal band gap energy of 1.45 eV, high photovoltaic conversion efficiency, low cost and stable performance. The deposition methods and preparation conditions for the fabrication of CdTe are very important for the achievement of high solar cell conversion efficiency. There are some rearranged reports about the deposition methods available for the preparation of CdTe thin films such as close spaced sublimation (CSS), physical vapor deposition (PVD), vacuum evaporation, vapor transport deposition (VTD), closed space vapor transport, electrodeposition, screen printing, spray pyrolysis, metalorganic chemical vapor deposition (MOCVD), and RF sputtering. The RF sputtering method for the preparation of CdTe thin films has important advantages in that the thin films can be prepared at low growth temperatures with large-area deposition suitable for mass-production. The authors reported that the optical and electrical properties of CdTe thin film were closely connected by the thickness-uniformity of the film in the previous study [1], which means that the better optical absorbance and the higher carrier concentration could be obtained in the better condition of thickness-uniformity for CdTe thin film. The thickness-uniformity could be controlled and improved by the some process parameters such as vacuum level and RF power in the sputtering process of CdTe thin films. However, there is a limitation to improve the thickness-uniformity only in the preparation process [1]. So it is necessary to introduce the external or additional method for improving the thickness-uniformity of CdTe thin film because the cell size of thin film solar cell will be enlarged. Therefore, the authors firstly applied the chemical mechanical polishing (CMP) process to improving the thickness-uniformity of CdTe thin films with a G&P POLI-450 CMP polisher [2]. CMP process is the most important process in semiconductor manufacturing processes in order to planarize the surface of the wafer even over 300 mm and to form the copper interconnects with damascene process. Some important CMP characteristics for CdTe were obtained including removal rate (RR), WIWNU%, RMS roughness, and peak-to-valley roughness [2]. With these important results, the CMP process for CdTe thin films was performed to improve the thickness-uniformity of the sputtering-deposited CdTe thin film which had the worst two thickness-uniformities of them. Some optical properties including optical transmittance and absorbance of the CdTe thin films were measured by using a UV-Visible spectrophotometer (Varian Techtron, Cary500scan) in the range of 400 - 800 nm. After CMP process, the thickness-uniformities became better than that of the best condition in the previous sputtering process of CdTe thin films. Consequently, the optical properties were directly affected by the thickness-uniformity of CdTe thin film. The absorbance of CdTe thin films was improved although the thickness of CdTe thin film was not changed.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1632-1639
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• 2004

Numerical calculation has been performed to investigate the transport phenomena in the horizontal reactor which has two different gas inlets for MOCVD(metalorganic chemical vapor deposition). The full elliptic governing equations for continuity, momentum, energy and chemical species are solved by using the commercial code FLUENT. It is investigated how thermal characteristics, reactor geometry, and the operating parameters affect flow fields, mass fraction of each reactants. The numerical simulations demonstrate that flow rate of each species, inlet geometry of the reactor, and its distance from the susceptor as well as the inclination of upper wall of reactor can be used effectively to optimize reactor performance. The commonly used idealized boundary conditions are also investigated to predict flow phenomena in the actual deposition system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.65-65
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• 2009

High temperature silicon carbide Schottky diode was fabricated with Au deposited on poly 3C-SiC thin film grown on p-type Si(100) using atmospheric pressure chemical vapor deposition. The charge transport mechanism of the diode was studied in the temperature range of 300 K to 550 K. The forward and reverse bias currents of the diode increase strongly with temperature and diode shows a non-ideal behavior due to the series resistance and the interface states associated with 3C-SiC. The charge transport mechanism is a temperature activated process, in which, the electrons passes over of the low barriers and in turn, diode has a large ideality factor. The charge transport mechanism of the diode was analyzed by a Gaussian distribution of the Schottky barrier heights due to the Schottky barrier inhomogeneities at the metal-semiconductor interface and the mean barrier height and zero-bias standard deviation values for the diode was found to be 1.82 eV and $s_0$=0.233 V, respectively. The interface state density of the diode was determined using conductance-frequency and it was of order of $9.18{\times}10^{10}eV^{-1}cm^{-2}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.85-85
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• 2010

Graphene, the building block of graphite, is one of the most promising materials due to their fascinating electronic transport properties. The pseudo-two-dimensional sp2 bonding in graphene layers yields one of the most effective solid lubricants. In this poster, we present the correlation between electrical and nanomechanical properties of graphene layer grown on Cu/Ni substrate with CVD (Chemical Vapor Deposition) method. The electrical (current and conductance) and nanomechanical (adhesion and friction) properties have been investigated by the combined apparatus of friction force microscopy/conductive probe atomic force microscopy (AFM). The experiment was carried out in a RHK AFM operating in ultrahigh vacuum using cantilevers with a conductive TiN coating. The current was measured as a function of the applied load between the AFM tip and the graphene layer. The contact area has been obtained with the continuum mechanical models. We will discuss the influence of mechanical deformation on the electrical transport mechanism on graphene layers.

• 한국산학기술학회논문지
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• 제19권9호
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• pp.536-542
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• 2018

이산화주석은 Rutile 구조를 갖는 Oxygen-Deficient n-type 반도체 물질로서, $H_2$, CO, $CO_2$ 등의 가스 분자가 표면에 흡착되면 전기저항이 변하는 특성을 가지고 있고, 이러한 성질을 활용하면 다양한 가스의 감지가 가능하기 때문에 가스센서로 연구가 활발히 이루어지고 있다. 나노구조물의 경우 Bulk 상태보다 체적 대비 표면적비가 높기 때문에 기체의 흡착이 유리하고, 가스 센서의 성능이 향상될 수 있다. 본 연구에서는 Thermal CVD 공정을 이용하여 SnO Nanoplatelet을 Si 기판위에 Dense하게 성장시켰다. 기상 수송 방법(Vapor Transport Method)으로 성장된 SnO 나노구조물을 Thermal CVD System을 이용하여 산소분위기에서 $830^{\circ}C$ 및 $1030^{\circ}C$에서 열처리(Post-Annealing)하여 $SnO_2$ 상(Phase)을 갖도록 하였다. 열처리 과정동안 쳄버의 압력을 4.2 Torr로 일정하게 유지시켰다. 열처리 된 SnO 나노구조물의 결정학적 특성을 Raman Spectroscopy 및 XRD 분석을 통하여 확인하였고, 형태학적 변화를 주사전사현미경(Scanning Electron Microscopy)을 통하여 확인하였다. 분석결과 SnO 나노구조물은 열처리 과정을 통하여 $SnO_2$ 나노구조물로 상변환 되었다.

• 대한금속재료학회지
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• 제49권2호
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• pp.187-191
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• 2011

In order to obtain a suitable back contacting electrode for $Cu(InGa)Se_2$-based photovoltaic devices, a molybdenum thin film was deposited using a chemical vapor transport (CVT) during the hydrogen reduction of $MoO_3$ powder. A $MoO_2$ thin film was successfully deposited on substrates by using the CVT of volatile $MoO_3(OH)_2$ at $550^{\circ}C$ for 60 min in a $H_2$ atmosphere. The Mo thin film was obtained by reduction of $MoO_2$ at $650^{\circ}C$ in a $H_2$ atmosphere. The Mo thin film on the substrate presented a low sheet resistance of approximately $1{\Omega}/sq$.

• 한국진공학회지
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• 제12권S1호
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• pp.95-99
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• 2003

We successfully grew InN/GaN single quantum well structures by metal-organic chemical vapor deposition and confirmed their formation by optical and structural measurements. We speculate that relatively high growth temperature ($730^{\circ}C$) of InN layer enhanced the formation of 2-dimensional quantum well structures, presumably due to high adatom mobility. As the growth interruption time increased, the PL emission efficiency from InN layer improved with peak position blue-shifted and the dislocation density decreased by one order of magnitude. The high resolution cross-sectional TEM images clearly showed that the InN layer thickness reduced from 2.5 nm (without GI) to about I urn (with 10 sec GI) and the InN/GaN interface became very flat with 10 sec GI. We suggest that decomposition and mass transport processes on InN during GI is responsible for these phenomena.