• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.232-232
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• 2010

정보화 산업의 발달은 DRAM, flash memory 등을 포함한 기존의 반도체 메모리 소자를 대체할 수 있는 차세대 메모리 소자에 대한 개발을 요구하고 있다. 특히 magnetic random access memory (MRAM)는 SRAM과 대등한 고속화 그리고 DRAM 보다 높은 기록 밀도가 가능하고 낮은 동작 전압과 소비전력 때문에 대표적인 차세대 비휘발성 메모리로 주목받고 있다. 또한 MRAM소자의 고집적화를 위해서 우수한 프로파일을 갖고 재증착이 없는 나노미터 크기의 magnetic tunnel junction (MTJ) stack의 건식 식각에 대한 연구가 선행되어야 한다. 본 연구에서는 고밀도 반응성 이온 식각법(Inductively coupled plasma reactive ion etching; ICPRIE)을 이용하여 재증착이 없이 우수한 식각 profile을 갖는 CoFeB과 IrMn 박막을 형성하고자 하였다. Photoresist(PR) 및 Ti 박막의 두 가지 마스크를 이용하여 HBr/Ar, HBr/$O_2$/Ar 식각 가스들의 농도를 변화시키면서 CoFeB과 IrMn 박막의 식각 특성들이 조사되었다. 자성 박막과 동일한 조건에 대하여 hard mask로서 Ti가 식각되었다. 좋은 조건을 얻기 위해 HBr/Ar 식각 가스를 이용 식각할 때 pressure, bias voltage, rf power를 변화시켰고 식각조건에서 Ti 하드마스크에 대한 자성 박막들의 selectivity를 조사하고 식각 profile을 관찰하였다. 식각 속도를 구하기 위해 alpha step(Tencor P-1)이 사용되었고 또한 field emission scanning electron microscopy(FESEM)를 이용하여 식각 profile을 관찰함으로써 최적의 식각 가스와 식각 조건을 찾고자 하였다.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.526-530
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• 2012

Silica-based ceramic-matrix composites have shown promise as advanced materials for many applications such as chemical catalysts, ceramics, pharmaceuticals, and electronics. $SiO_2$-CuO-$CeO_2$ multi-component powders and their thin film, using an oxalic acid template as a chelating agent, have larger surface areas and more uniform pore size distribution than those of inorganic acid catalysts. $SiO_2$-CuO-$CeO_2$ composite powders were synthesized using tetraethylorthosilicate, copper (II) nitrate hemi (pentahydrate), and cerium (III) nitrate hexahydrate with oxalic acid as template or pore-forming agent. The process of thermal evolution, the phase composition, and the surface morphology of these powders were monitored by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffractometry (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDXS). The mesoporous property of the powders was observed by Brunner-Emmett-Teller surface (BET) analysis. The improved surface area of this powder template with oxalic acid was $371.4m^2/g$. This multi-component thin film on stainless-steel was prepared by sol-gel dip coating with no cracks.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.241-242
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• 2012

산화아연 씨앗층을 졸-겔 스핀코팅법으로 석영기판위에 증착시킨 후, 수열합성법을 이용하여 갈륨의 양을 0에서 2.0 at.% 으로 변화를 주어 갈륨이 도핑된 산화아연 나노막대를 성장하였다. 산화아연과 갈륨이 도핑된 산화아연 나노막대의 구조적 광학적 특성을 조사하기 위해 field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), 그리고 ultraviolet-visible spectroscopy를 이용하였다. 일정한 산화아연과 갈륨이 도핑된 산화아연 나노막대는 육각형형태로 성장하였다. XRD 데이터로부터, 산화아연과 갈륨이 도핑된 산화아연 나노막대의 스트레스는 각각 -0.022 (0 at.%), 0.097 (0.5 at.%), 0.165 (1.0 at.%), 0.177 (1.5 at.%), 0.182 GPa (2.0 at.%) 였다. PL 스펙트라에서 얻어진 반가폭(The full width at half maximum)은 갈륨의 양이 0에서 2.0 at.%로 증가함에 따라 127에서 171 meV로 증가하였다. Urbach 에너지는 68 (0 at.%), 97 (0.5 at.%), 108 (1.0 at.%), 104 (1.5 at.%), 127 meV (2.0 at.%)였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.243-244
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• 2012

산화아연 나노구조를 금을 금속촉매로 사용하여 실리콘 기판위에 기상이동법으로 성장하였다. 성장할 때 소스(source)와 기판 사이의 거리는 5에서 50 mm로 변화를 주며 아르곤과 산소 분위기에서 $900^{\circ}C$로 성장하였다. 산화아연 나노구조의 구조적 및 광학적 특성을 조사하기 위해 field-emission scanning electron microscopy, X-ray diffraction (XRD), 그리고 photoluminescence (PL)를 이용하였다. 산화아연 나노구조는 나노선과 나노입자의 형태로 성장하였다. 산화아연 나노구조의 광학적 특성은 소스와 기판사이의 거리가 가까울수록 향상되었다. 특히, 소스와 기판사이의 거리가 5 mm 일 때, 산화아연 나노선이 관찰되었으며 XRD 와 PL 분석에서 나타난 반가폭 (full width at half maximum)은 $0.061^{\circ}$ 와 96 meV로써 가장 작았다. 산화아연 나노선은 산화아연 나노입자와 비교하여, 결정성 및 광학적 특성이 우수하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.245-246
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• 2012

Al 농도를 0 부터 2 at.% 까지 조절하여 도핑된 $Cd_{0.5}Zn_{0.5}O$ 박막을 석영 기판 위에 성장하였다. Al 도핑된 $Cd_{0.5}Zn_{0.5}O$ 박막의 구조적, 광학적 특성을 조사하기 위해 field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), 그리고 ultraviolet-visible (UV) spectroscopy을 사용하였다. 광학적 밴드갭은 Al 도핑 농도가 증가함에 따라 2.874 (0 at.%), 2.874 (0.5 at.%), 3.029 (1.0 at.%), 3.038 (1.5 at.%), 3.081 eV (2.0 at.%)로 증가하였다. Urbach energy는 도핑 농도에 따라 각각 464 (0 at.%), 585 (0.5 at.%), 571 (1.0 at.%), 600 (1.5 at.%), 470 meV (2.0 at.%)이었다. 또한, Al 농도가 증가함에 따라 $Cd_{0.5}Zn_{0.5}O$ 박막의 표면, 구조적 및 광학적 특성이 크게 변화되었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.211-212
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• 2012

ZnO submicron particles were grown on Au-catalyzed Si substrate by a vapor phase transport (VPT) growth process under different mixture gas ratio at growth temperature of $900^{\circ}C$. The structural and optical properties of the ZnO submicron particles were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL). The ZnO submicron particles could be clustered with the $O_2/Ar$ mixture gas ratio(%) higher than 10%, and it was mainly determined by the gas ambient. Particularly, when the $O_2/Ar$ mixture gas ratio was 30%, it was observed the ZnO submicron particles with diameters in the range of 125 to 500 nm and the narrowest full width at half maximum (FWHM) of XRD and PL spectra with $0.121^{\circ}$ and 92 meV, respectively. It was found that the structural and optical properties of the ZnO submicron particles were improved with increasing the $O_2/Ar$ mixture gas ratio through the XRD and PL spectra.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.90-100
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• 2010

Micro-conductive patterns were microfabricated on an insulating substrate ($SiO_2$) surface by a selective electroless nickel plating process in order to investigate the formation of seed layers. To fabricate micro-conductive patterns, a thin layer of metal (Cu.Cr) was deposited in the desired micropattern using laser-induced forward transfer (LIFT). and above this layer, a second layer was plated by selective electroless plating. The LIFT process. which was carried out in multi-scan mode, was used to fabricate micro-conductive patterns via electroless nickel plating. This method helps to improve the deposition process for forming seed patterns on the insulating substrate surface and the electrical conductivity of the resulting patterns. This study analyzes the effect of seed pattern formation by LIFT and key parameters in electroless nickel plating during micro-conductive pattern fabrication. The effects of the process variables on the cross-sectional shape and surface quality of the deposited patterns are examined using field emission scanning electron microscopy (FE-SEM) and an optical microscope.

• Korean Journal of Metals and Materials
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• v.50 no.8
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• pp.557-562
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• 2012

Self-organized ruthenium (Ru) dots were fabricated by $400^{\circ}C$ RTA (rapid thermal annealing) and ALD (atomic layer deposition). The dots were produced under the $400^{\circ}C$ RTA conditions for 10, 30 and 60 seconds on all Si(100)/200 nm-SiO2, glass, and glass/fluorine-doped tin oxide (FTO) substrates. Electrical sheet resistance, and surface microstructure were examined using a 4-point probe and FE-SEM (field emission scanning electron microscopy). Ru dots were observed when a 30 nm-Ru layer on a Si(100)/200 nm-SiO2 substrate was annealed for 10, 30 and 60 seconds, whereas the dots were only observed on a glass substrate when a 50 nm-Ru layer was annealed on glass. For a glass/FTO substrate, RTA <30 seconds was needed for 30 nm Ru thick films. Those dots can increase the effective surface area for silicon and glass substrates by up to 5-44%, and by 300% for the FTO substrate with a < $20^{\circ}$ wetting angle.

• Journal of Radiation Industry
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• v.8 no.1
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• pp.17-22
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• 2014

In this study, we prepared CdTe/CdS solar cells using a thermal vacuum evaporation method. In particular, $CdCl_2$ treatment was attempted using this same method at $400^{\circ}C$ for 30 min. The prepared CdTe/CdS solar cells were investigated using Fouier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FE-SEM), and a solar simulator system including light absorption properties, morphological properties, and power conversion efficiency (PCE). In addition, we investigated the gamma-irradiation treatment at dose rates of 0 Gy, 500 Gy, 1 kGy, 10 kGy, and 30 kGy. The characteristics of gamma-irradiation treatment were studied based on the same method described above. In particular, it showed increased values as 0.826% higher than the non-irradiation of 0.448% from PCE analysis.

• Journal of Magnetics
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• v.16 no.1
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• pp.27-30
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• 2011

Nano-sized manganese ferrite powders and films, $MnFe_2O_4$, were fabricated by the sol-gel method, and the effects of annealing temperature on the crystallographic and magnetic properties were studied by using X-ray diffractometry, field emission scanning electron microscopy, M$\"{o}$ssbauer spectroscopy, and vibrating sample magnetometry. X-ray diffraction spectroscopy of powder samples annealed above 523 K indicated the presence of spinel structure, and the film samples annealed above 773 K also had spinel structure. The particle size increased with the annealing temperature. For the powder samples, the Mossbauer spectra annealed above 573 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of $Fe^{3+}$ ions. Using the M$\"{o}$ssbauer subspectrum area ratio the cation distribution could be written as ($Mn_{0.52}Fe_{0.48}$) $[Mn_{0.48}Fe_{1.52}]$ $O_4$. However the spectrum annealed at 523 K only showed as a doublet due to a superparamagnetic phase. As the annealing temperature was increased, the saturation magnetization and the corecivity of the powder samples increased, as did the coercivity of film samples.