• 한국전기전자재료학회논문지
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• 제25권9호
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• pp.717-722
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• 2012

In this work, we study on the effects of the oxygen pressure on the structural and crystalline of MgZnO thin films. MgZnO thin films were deposited on p-Si (111) substrates by using pulsed laser deposition. The X-ray diffraction analysis and energy-dispersive X-ray results revealed that as the oxygen pressure increased and Mg content in the MgZnO films decreased. Also Crystal structure was changed from cubic rock salt to hexagonal wurtzite. Alpha step and atomic force microscopy results showed that the thickness of the films are about 100 nm, and it has been found that the MgZnO (002) preferred orientation were deposited with increasing the oxygen pressure. Therefore, the effect of the preferred orientation, the crystallization grew in the form of the columnar; Grain size and RMS of the films were increased with increasing oxygen pressure.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.248-248
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• 2011

ZnO was grown on a Au-catalyzed Si(100) substrate by using a simple vapor phase transport (VPT) with a mixture of zinc oxide and graphite powders. The ZnO grown at 800$^{\circ}C$ had a soccer ball structure with diameters of <500 nm. The ZnO soccer ball structure was, for the first time, observed in this work. The optical properties of the ZnO soccer balls were investigated by photoluminescence (PL). In the room-temperature (RT) PL of the ZnO soccer balls, a strong near-band-edge emission (NBE) and a weak deep-level emission were observed at 3.25 and 2.47 eV (green emission), respectively. The weak deep-level emission (DLE) at around 2.47 eV (green emission) is caused by impurities and structural defects. The FWHM of the NBE peak from the ZnO soccer balls was 110 meV. In addition, the PL intensity ratio of the NBE to DLE was about 4. The temperature-dependent PL was also carried out to investigate the mechanism governing the quenching behavior of the PL spectra.

• 설비공학논문집
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• 제20권4호
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• pp.274-279
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• 2008

In the perspective of saving energy in buildings, high performance of insulation and air tightness for improving the heating and the cooling efficiency has brought the positive effect in an economical view. However, these building energy saving technologies cause the lack of ventilation, which is the direct cause of increasing the indoor contaminants, and it is also very harmful to residents because they spend over 90% of their time in the indoor area. Therefore, the ventilation is important to keep indoor environment clean and it can also save energy consumption. In this study, a HEPA type breathing wall is designed as a passive ventilation system to collect airborne particles and to supply fresh outdoor air. To make fine porous structures, polymer nano fibers which were made by electro spinning method are used as a precursor. The nano fibers are coated with SiO2 nano particles and finally the HEPA type breathing wall is made by sintering in the electric furnace at $300\sim500^{\circ}C$. The pressure drops of nano ceramic structure are 8.2, 25.5 and 44.9 mmAq at the face velocity of 2.0, 5.9 and 8.8 cm/s, respectively. Also the water vapor permeability is $3.6g/m^2{\cdot}h{\cdot}mmHg$. In this research, the porous nano ceramic structures are obtained and the possibility for the usage of a material for HEPA type breathing wall can be obtained.

• 한국전기전자재료학회논문지
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• 제28권4호
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• pp.244-248
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• 2015

We proposed and demonstrated the double layered metallic nano-hole structure using polystyrene beads process to enhance the sensitivity of surface plasmon resonance (SPR). The double layered SPR structures are calculated using the finite-difference time-domain (FDTD) method for the width, thickness, and period of the metallic nano-hole structures. The thickness of the metal film and the metallic nano-hole is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The double layered SPR structures are fabricated with monolayer polystyrene beads of 420 nm wide. The sensitivities of the conventional SPR sensor and the double layered SPR sensor are obtained to 42.2 and 52.1 degree/RIU, respectively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.170.1-170.1
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• 2016

$Bi_2Te_3$ has long been studied for its excellent thermoelectric characteristics. Recently, this material has been known as a topological insulator (TI). The surface states within the bulk band gap of a TI, which are protected by the time reversal symmetry, contribute to the conduction at the surface, while the bulk is in insulating state. In contrast to the bulk defects tuning the chemical potential to the Dirac energy, the native defects near the surface are expected not to change the shape of the Fermi surface and the related spin structure. Using scanning tunneling microscopy (STM), we have systematically characterized surface or near surface defects in p- and n- doped $Bi_2Te_3$, and identified their structure by first principles calculations. In addition, bias-polarity dependences of STM images revealed the electron donor/acceptor nature of each defect. A detailed theoretical study of the surface states near the Dirac energy reveals the robustness of the Dirac point, which verifies the effectiveness of the disturbance on the backscattering from various kinds of defects.

• 한국진공학회지
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• 제15권2호
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• pp.209-215
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• 2006

PL (photoluminescence), PLE (PL excitation) 그리고 근 적외선 투과 분광법을 활용하여 InAsGa/GaAs 우물 내 InAs 양자점 구조의 광학적 특성과 전자 버금 띠 구조에 대하여 연구하였다. 투과 스펙트럼과 PLE 스펙트럼으로부터 InAs 양자점 내 세 개의 구속 상태와 InGaAs/GaAs 우물 내에 두 개의 구속 상태가 존재함을 발견하였고, 광전류 스펙트럼에서 관측된 버금 띠 사이 전이들과 연관지어 해석하였다.

• 대한전자공학회논문지SD
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• 제40권12호
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• pp.1-9
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• 2003

본 논문에서는 cobalt interlayer와 TiN capping을 적용한 Ni-Silicide 구조를 제안하여 100 ㎜ CMOS 소자에 적용하고 소자 특성 연구를 하였다. Ni-Silicide의 취약한 열 안정성을 개선하기 위해 열 안정성이 우수한 Cobalt interlayer이용하여 silicide의 열화됨을 개선하였고 또한 silicide 계면의 uniformity를 향상하기 위해 TiN capping을 동시에 적용하였다. 100 ㎚ CMOS 소자에 제안한 Co/Ni/TiN 구조를 적용하여 700℃, 30분에서의 열처리 시에도 silicide의 낮은 면저항과 낮은 접합 누설 전류가 유지되었으며 100 ㎚이하 소자의 특성 변화도 거의 없음을 확인하였다. 따라서 제안한 Co/Ni/TiN 구조가 NiSi의 열 안정성을 개선시킴으로써 100 ㎚ 이하의 Nano CNOS 소자에 매우 적합한 Ni-Silicide 특성을 확보하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.359-359
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• 2011

This study reports the H2S gas sensing properties of CuO / ZnO nano-hetero structure bundle and the investigation of gas sensing mechanism. The 1-Dimensional ZnO nano-structure was synthesized by hydrothermal method and CuO / ZnO nano-heterostructures were prepared by photo chemical reaction. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectra confirmed a well-crystalline ZnO of hexagonal structure. In order to improve the H2S gas sensing properties, simple type of gas sensor was fabricated with ZnO nano-heterostructures, which were prepared by photo-chemical deposition of CuO on the ZnO nanorods bundle. The furnace type gas sensing system was used to characterize sensing properties with diluted H2S gas (50 ppm) balanced air at various operating temperature up to 500$^{\circ}C$. The H2S gas response of ZnO nanorods bundle sensor increased with increasing temperature, which is thought to be due to chemical reaction of nanorods with gas molecules. Through analysis of X-ray photoelectron spectroscopy (XPS), the sensing mechanism of ZnO nanorods bundle sensor was explained by well-known surface reaction between ZnO surface atoms and hydrogen sulfide. However at high sensing temperature, chemical conversion of ZnO nanorods becomes a dominant sensing mechanism in current system. Photo-chemically fabricated CuO/ZnO heteronanostructures show higher gas response and higher current level than ZnO nanorods bundle. The gas sensing mechanism of the heteronanostructure can be explained by the chemical conversion of sensing material through the reaction with H2S gas.

• 한국재료학회지
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• 제20권3호
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• pp.142-147
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• 2010

Nano-sized $BaNd_2Ti_5O_{14}$ powders were prepared by the spray pyrolysis process. Sucrose used as the organic additive enabled the formation of nano-sized $BaNd_2Ti_5O_{14}$ powders. The powders prepared from the spray solution without sucrose had a spherical shape, dense structure and micron size before and after calcination. However, the precursor powders prepared from the spray solution with sucrose had a large size, and hollow and porous morphology. The precursor powders had an amorphous crystal structure because of the short residence time of the powders inside the hot wall reactor. The complete decomposition of sucrose did not occur inside the hot wall reactor. Therefore, the precursor powders obtained from the spray solution with sucrose of 0.5M had a carbon content of 39.2wt.%. The powders obtained from the spray solution with sucrose of 0.5M had a slightly aggregated structure of nano-sized primary powders of $BaNd_2Ti_5O_{14}$ crystalline phase after calcination at $1000^{\circ}C$. The calcined powders turned into nano-sized $BaNd_2Ti_5O_{14}$ powders after milling. The mean size of the $BaNd_2Ti_5O_{14}$ powders was 125 nm.

• 한국자기학회지
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• 제14권4호
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• pp.149-161
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• 2004

나노기술과 정보기술의 융합은 이제 성숙 단계에 있는 정보화시대에 중요한 역할을 할 것으로 예상된다. 특히, 한국 산업에서의 정보 기술의 역할을 고려할 때, NT-IT 기술 융합은 매우 중요하다. 나노 소재는 그 크기가 나노미터 크기로 작은 것을 의미하며, 나노 크기에서 독특한 물성을 나타내는 특성을 가지고 있다 자기조립 기술을 활용하여 보텀업 공정을 수행하여 나노 크기의 정보 소재 및 소자를 구현한다. 이러한 기술은 생물체 등에서 일어나는 원자나 분자의 자기 조립 현상과 유사하다. 유기. 무기 템플릿을 이용한 정보 소재 개발 연구는 Guided Self Assembly유기물 나노 템플릿의 개발 및 AAO무기물 나노 템플릿을 활용한 나노 구조물 형성과 이를 응용한 정보기술과의 융합에 관해 연구이다. Nano structuring을 위해 Electroforming, Sol-gel processing, ionized Physical vapor deposition, ion beam implantation 법 등을 사용하며, 정보기술에 필요한 핵심 요소 기술을 개발한다. 형성된 Nano structure의 전기적 특성 평가 및 미세 구조 분석 및 응용을 고려한 소자 특성 평가를 통해서, IT분야에 적용 가능한 정보소재를 개발한다.