• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.207-207
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• 2011

Amorphous transparent oxide semiconductors (a-TOS) have been widely studied for many optoelectronic devices such as AM-OLED (active-matrix organic light emitting diodes). Recently, Nomura et al. demonstrated high performance amorphous IGZO (In-Ga-Zn-O) TFTs.1 Despite the amorphous structure, due to the conduction band minimum (CBM) that made of spherically extended s-orbitals of the constituent metals, an a-IGZO TFT shows high mobility.2,3 But IGZO films contain high cost rare metals. Therefore, we need to investigate the alternatives. Because Aluminum has a high bond enthalpy with oxygen atom and Alumina has a high lattice energy, we try to replace Gallium with Aluminum that is high reserve low cost material. In this study, we focused on the electrical properties of IZO:Al thin films as a channel layer of TFTs. IZO:Al were deposited on unheated non-alkali glass substrates (5 cm ${\times}$ 5 cm) by magnetron co-sputtering system with two cathodes equipped with IZO target and Al target, respectively. The sintered ceramic IZO disc (3 inch ${\phi}$, 5 mm t) and metal Al target (3 inch ${\phi}$, 5 mm t) are used for deposition. The O2 gas was used as the reactive gas to control carrier concentration and mobility. Deposition was carried out under various sputtering conditions to investigate the effect of sputtering process on the characteristics of IZO:Al thin films. Correlation between sputtering factors and electronic properties of the film will be discussed in detail.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.185-185
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• 2011

ZnTe semiconductor is very attractive materials for optoelectronic devices in the visible green spectral region because of it has direct bandgap of 2.26 eV. The prototypes of ZnTe light emitting diodes (LEDs) have been reported [1], showing that their green emission peak closely matches the most sensitive region of the human eye. Another application to photovoltaics proved that ZnTe is useful for the production of high-efficiency multi-junction solar cells [2,3]. By using the pulse laser deposition system, ZnTe thin films were deposited on ZnO thin layer, which is grown on (0001) Al2O3substrates. To produce the plasma plume from an ablated ZnO and ZnTe target, a pulsed (10 Hz) YGA:Nd laser with energy density of 95 mJ/$cm^2$ and wavelength of 266 nm by a nonlinear fourth harmonic generator was used. The laser spot focused on the surface of the ZnO and ZnTe target by using an optical lens was approximately 1 mm2. The base pressure of the chamber was kept at a pressure around $10^{-6}$ Torr by using a turbo molecular pump. The oxygen gas flow was controlled around 3 sccm by using a mass flow controller system. During the ZnTe deposition, the substrate temperature was $400^{\circ}C$ and the ambient gas pressure was $10^{-2}$ Torr. The structural properties of the samples were analyzed by XRD measurement. The optical properties were investigated by using the photoluminescence spectra obtained with a 325 nm wavelength He-Cd laser. The film surface and carrier concentration were analyzed by an atomic force microscope and Hall measurement system.

• 한국결정성장학회지
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• 제28권3호
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• pp.106-111
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• 2018

할라이드 페로브스카이트 나노결정은 고색순도 및 우수한 발광특성을 바탕으로 LED 응용에 대한 연구가 활발히 진행되고 있다. 고온주입법을 통하여 $CsPbX_3$(X = I, Br, and Cl) 나노결정을 합성하였고 할로젠 이온의 조성 변화를 통하여 발광파장을 제어하였다. 고분자 바인더를 사용하여 녹색과 적색의 필름을 제작하였다. 합성된 나노결정 및 제작된 필름의 우수한 광특성을 확인하였고, 이를 InGaN 청색 LED칩에 적용하여 우수한 색영역의 wLED를 구현하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.285-285
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• 2013

Recently, hexagonal boron nitride (h-BN), which is III-V compound of boron and nitride by strong covalent sp2 bonds has gained great interests as a 2 dimensional insulating material since it has honeycomb structure with like graphene with very small lattice mismatch (1.7%). Unlike graphene that is semi-metallic, h-BN has large band gap up to 6 eV while providing outstanding properties such as high thermal conductivity, mechanical strength, and good chemical stability. Because of these excellent properties, hBN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Low pressure and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) methods have been investigated to synthesize h-BN by using ammonia borane as a precursor. Ammonia borane decomposes to polyiminoborane (BHNH), hydrogen, and borazine. The produced borazine gas is a key material that is a used for the synthesis of h-BN, therefore controlling the condition of decomposed products from ammonia borane is very important. In this paper, we optimize the decomposition of ammonia borane by investigating temperature, amount of precursor, and other parameters to fabricate high quality monolayer h-BN. Synthesized h-BN is characterized by Raman spectroscopy and its absorbance is measured with UV spectrophotometer. Topological variations of the samples are analyzed by atomic force microscopy. Scanning electron microscopy and Scanning transmission Electron microscopy are used for imaging and analysis of structures and surface morphologies.

• 대한금속재료학회지
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• 제48권4호
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• pp.320-325
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• 2010

NiO thin films were deposited by radio frequency magnetron sputtering on glass substrates. The processing variables of the oxygen content, sputtering power, and pressure were varied to investigate the electrical properties and surface morphology of NiO films. It was found that the resistivity of NiO films at $1.22{\times}10^2{\Omega}cm$ (2.5% $O_2$ in Ar gas) was greatly reduced to$ 2.01{\times}10^{-1}$ ${\Omega}cm$ (100% oxygen) under a typical sputtering condition of 6 mTorr and 200 watts. In an effort to observe the resistivity variances, the sputtering power was varied from 80 to 200 watts at 6 mTorr with 100% $O_2$. However, the resistivity of the NiO films changed in the range of $10^{-1}-10^{-2}$ ${\Omega}cm$. The dependence on the sputtering power was therefore found to be weak in this experiment. When the sputtering pressure was changed from 3 to 60 mTorr at 200 watts with 100% $O_2$, the resistivity of the NiO films showed the lowest value of $5.8{\times}10^{-3}$ ${\Omega}cm$ at 3 mTorr, which is close to that of commercial ITO films (${\sim}10^{-4}$ ${\Omega}cm$). As the sputtering pressure increased, the resistivity also increased to 4.67 cm at 60 mTorr. The surface morphology of the NiO films was also checked by Atomic Force Microscopy. It was found that the RMS surface roughness values ranged from 0.6 to 1.5 nm and thtthe dependence on the sputtering parameters was weak.

• Composites Research
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• 제35권4호
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• pp.298-302
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• 2022

할라이드 페로브스카이트 물질은 우수한 광전특성으로 인해 차세대 디스플레이에 응용시킬 물질로서 주목받고 있다. 본 연구에서는 다공성 SiO₂ 나노입자의 기공 내부에서 제한시킨 결정 성장을 통하여 할라이드 페로브스카이트의 안정성 문제를 해결한, CsPbBr₃의 새로운 소결법을 제안한다. 최적의 소결 조건에서 소결된 CsPbBr₃-SiO₂ 나노입자는 515 nm의 발광 피크를 나타낸다. CsPbBr₃-SiO₂ 나노입자는 소결 과정 중 닫힌 기공에 말미암아 몇 종의 극성 용매 속에서도 안정적으로 발광 특성을 유지할 수 있었으며, 이는 디스플레이용 색변환 필름으로서의 응용 가능성을 보여준다.

• Computers and Concrete
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• 제29권 6호
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• pp.375-391
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• 2022

This paper examined the impact of the cross-sectional structure on the structural results under different loading conditions of reinforced concrete (RC) members' management limited in Carbon Fiber Reinforced Polymers (CFRP). The mechanical properties of CFRC was investigated, then, totally 32 samples were examined. Test parameters included the cross-sectional shape as square, rectangular and circular with two various aspect rates and loading statues. The loading involved concentrated loading, eccentric loading with a ratio of 0.46 to 0.6 and pure bending. The results of the test revealed that the CFRP increased ductility and load during concentrated processing. A cross sectional shape from 23 to 44 percent was increased in load capacity and from 250 to 350 percent increase in axial deformation in rectangular and circular sections respectively, affecting greatly the accomplishment of load capacity and ductility of the concentrated members. Two Artificial Intelligence Models as Extreme Learning Machine (ELM) and Particle Swarm Optimization (PSO) were used to estimating the tensile and flexural strength of specimen. On the basis of the performance from RMSE and RSQR, C-Shape CFRC was greater tensile and flexural strength than any other FRP composite design. Because of the mechanical anchorage into the matrix, C-shaped CFRCC was noted to have greater fiber-matrix interfacial adhesive strength. However, with the increase of the aspect ratio and fiber volume fraction, the compressive strength of CFRCC was reduced. This possibly was due to the fact that during the blending of each fiber, the volume of air input was increased. In addition, by adding silica fumed to composites, the tensile and flexural strength of CFRCC is greatly improved.

• 한국전자통신학회논문지
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• 제19권1호
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• pp.39-46
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• 2024

본 연구에서는 고주파 마그네트론 스퍼터링 법으로 공정압력을 1에서 7mTorr 로 변화시켜 가며 GTZO (Ga-Ti-Zn-O)박막을 제작하여, 구조적 특성과 전기적 및 광학적 특성을 조사하였다. XRD측정을 통해 공정압력에 무관하게 모든 GTZO박막이 c-축으로 우선 성장함을 확인할 수 있었고, 1mTorr 에서 제작한 GTZO 박막이 반가폭 0.38˚ 로 가장 우수한 결정성을 나타내었다. 가시광 영역(400~800 nm)에서의 평균 투과도는 공정압력에 상관없이 80% 이상의 값을 나타내었고, 공정압력이 증가함에 따라 캐리어 농도가 감소하고 이로 인해 에너지 밴드갭이 좁아지는 Burstein - Moss 효과도 관찰할 수 있었다. 공정압력 1mTorr 에서 증착한 GTZO박막의 재료 평가 지수는 9.08 × 10³ Ω^-1·cm^-1 로 가장 우수한 값을 나타내었고 이때 비저항과 가시광 영역에서의 평균 투과도는 각각 5.12 × 10^-4 Ω·cm 과 80.64 % 이었다.

• 한국전자통신학회논문지
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• 제19권1호
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• pp.47-52
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• 2024

본 연구에서는 유리 기판 위에 BZO박막을 제작한 후, 열처리 온도가 박막의 전기적 및 광학적 특성에 미치는 영향을 조사하였다. XRD 분석 결과, 열처리 온도에 무관하게 모든 박막이 c-축 배향성을 나타내었다. 열처리 온도가 400에서 600℃ 로 증가함에 따라 반가폭(FWHM)은 1.65에서 1.07° 로 감소하였다. 가시광 영역(400-800nm)에서의 평균 투과도는 열처리 온도에 큰 영향 없이 85% 이상의 높은 값을 나타내었다. Hall 측정결과, 열처리 온도에 따라 캐리어 농도와 이동도는 증가하였고 비저항은 감소하였다. 600℃ 에서 열처리한 BZO박막의 비저항과 캐리어 농도는 각각 9.75 × 10^-2 Ω·cm 과 4.21×10¹⁹ cm^-3 로 가장 우수한 값을 나타내었다. 향후 BZO박막의 공정 조건과 열처리 조건을 최적화시킨다면, 차세대 광전자 소자에 응용될 수 있는 매우 유망한 재료로 주목받을 것으로 기대된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.422.1-422.1
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• 2016

Graphene quantum dots (GQDs), a new kind of carbon-based photo luminescent nanomaterial from chemically modified graphene oxide (CMGO) or chemically modified graphene (CMG), has attracted extensive research attention in the last few years due to its outstanding chemical, optical and electrical properties. To further extended its potential applications as optoelectronic devices, solar cells, bio and bio-sensors and so on, intensive research efforts have been devoted to the CMG. However, the CMG, a suspension of aqueous, have problematic since they are prone to agglomeration after drying a solvent. In this study, we synthesized the GQDs from graphite and deposited on silicon substrate by kinetic spray. The photo luminescent properties of deposited GQD films were analyzed and compared with initial GQDs suspension. In addition, its carbon properties were investigated with GQDs solution properties. The properties of deposited GQD films by kinetic spray were similar to that of the GQDs suspension in water. We could provide a pathway for silicon-based silicon based device applications. Finally, the well-adjusted GQD films with photo luminescence effects will show Energy-Down-Shift layer effects on silicon solar cells. The GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density (Jsc) was enhanced by about 2.94 % (0.9 mA/cm2) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).