• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.87-91
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• 2004

We have investigated the effects of W-N/Pt bottom electrode on the ferroelectric degradation of $Sr_{0.8}Bi_{2.4}Ta_2O_9(SBT)/Pt$ due to hydrogen annealing at $350^{\circ}C$ in $N_2$ gas atmosphere containing $5{\%}\;H_2$ gas for 1hr. As a result, inserting the W-N thin films between SBT and Pt, this W-N thin film prevents hydrogen molecules to be chemisorbed at the Pt electrode surface of at the electrode/ferroelectric interface during hydrogen annealing. These hydrogen atoms can diffuse into the SBT and react with the oxide causing the oxygen deficiency in the SBT film, which will result in the ferroelectric degradation. Experimental results show that W-N thin film is a good diffusion barrier during the hydrogen annealing.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.117-122
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• 2005

Electron Beam Physical Vapor Deposition (EB-PVD) is a typical technology for thermal barrier coating with Yttria Stabilized Zirconia (YSZ) on aero gas turbine engine. In this study EB-PVD method was used to fabricate dense YSZ film on NiO-YSZ as a electrolyte of Solid Oxide Fuel Cell (SOFC). Dense YSZ films of -10 $\mu$m thickness showed nano surface structure depending on deposition temperature. Electrical conductivities of YSZ film and electric power density of the single cell were evaluated after screen- printing $LaSrCoO_3$ as a cathode.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.6.1-6.1
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• 2010

원자층 증착 기술 (Atomic Layer Deposition)은 기판 표면에서 한 원자층의 화학적 흡착 및 탈착을 이용한 nano-scale 박막 증착 기술이기 때문에, 표면 반응제어가 우수하며 박막의 물리적 성질의 재현성이 우수하고, 대면적에서도 균일한 두께의 박막 형성이 가능하며 우수한 계단 도포성을 확보 할 수 있다. 최근 ALD에 의한 박막증착 방법 중 플라즈마를 이용한 ALD 증착 방법에 대한 다양한 연구가 진행되고 있다. 플라즈마는 반응성이 좋은 이온과 라디컬을 생성하여 소스간 반응성을 좋게 하여, 소스 선택의 폭을 넓어지게 하고, 박막의 성질을 좋게 하며, 생산성을 높일 수 있는 장점이 있다. 그러나 플라즈마를 사용함으로써 플라즈마 내에 이온들이 가속되서 박막 증착 중에 기판 및 박막에 손상을 입혀 박막 특성을 열화 시킬 가능성이 있다. 따라서 플라즈마 발생 영역을 기판으로부터 멀리 떨어뜨린 원거리 플라즈마 원자층 공정이 개발 되었다. 이 기술은 플라즈마에서 생성된 ion이 기판이나 박막에 닫기 전에 전자와 재결합 되거나 공정 chamber에서 소멸하여 그 영향을 최소하고 반응성이 좋은 라디칼과의 반응만을 유도하여 향상된 막질을 얻을 수 있도록 하였다. 따라서 이 원거리 플라즈마 원자층 증착기술은 나노 테크놀러지 소자 개발하기 위한 나노 박막 기술에 있어서 그 활용이 점점 확대될 것이다. 그 적용으로써 리모트 플라즈마 원자층 증착 방법을 이용한 고유전 물질 개발이 있다. 반도체 소자의 고집적화 및 고속화가 요구됨에 따라 집적회로의 크기를 혁신적으로 축소하여 스위칭 속도(switching speed)를 증가시키고, 전력손실 (power dissipation)을 줄이려는 시도가 이루어지고 있다. 그 중 하나로 고유전율 절연막은 트렌지스터 소자의 스케일링 과정에 수반하여 커지는 게이트 누설 전류를 억제하기 위한 목적으로 도입되었다. 유전율이 크면 동일한 capacitance를 내는데 필요한 물리적인 두께를 늘릴 수 있어 전자의 tunneling을 억제할 수 있고 전력손실을 줄일 수 있기 때문이다. 이와 같은 고유전율 물질이 게이트 산화막으로 사용되기 위해서 높은 유전상수 열역학적 안정성, 낮은 계면 전하밀도, 낮은 EOT, 전극 물질과의 양립성 등의 특성이 요구되는데, 이에 따라 많은 유전물질에 대한 연구가 진행되었다. 기존 gata oxide를 대체하기 위한 가장 유력한 후보 재료로 주목 받고 있는 high-k 물질들로는 Al2O3, HfO2, ZrO2, La2O3 등이 있다. 본 발표에서는 ALD의 종류에 따른 기술을 소개하고 그 응용으로 고유전율 물질 개발 연구 (고유전율 산화물 박막의 증착, 고유전율 산화물의 열적 안정성 평가, Flatband 매카니즘 규명, 전기적 물리적 특성 분석)에 대해서 발표 하고자 한다.

• Membrane Journal
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• v.30 no.5
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• pp.293-306
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• 2020

Increasing harmful effects of climate change, such as its effect on water scarcity, has led to a focus on developing effective water purification methods to obtain pure water. Additionally, rising levels of water pollution is increasing levels of environmental degradation, calling for sources of water treatment to remove contaminants. To purify water, osmotic processes across a semipermeable membrane can take place, and recent studies are showing that incorporating nanoparticles, including carbon quantum dots (CQDs), graphene carbon dots (GQDs), and graphene oxide quantum dots (GOQDs) are making thin film composite (TFC) membranes more effective by increasing water flux while maintaining similar levels of salt rejection, increasing the hydrophilicity of the membrane surface, showing bactericidal properties, exhibiting antifouling properties to prevent accumulation of bacteria or other microorganisms from reducing the effectiveness of the membrane, and more. In the review, the synthesis process, applications, functionality, properties, and the role of several types of quantum dots are discussed in the composite membrane for water purification.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.2
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• pp.201-212
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• 2011

Nanotechnology is the applied science which develops new materials and systems sized within 1 to 100 nanometer, and improves their physical, chemical, and biological characteristics by manipulating on an atomic and molecular scale. This nanotechnology has been applied to wide spectrum of industries resulting in production of various nanoparticles. It is expected that more nanoparticles will be generated and enter to natural water bodies, imposing great threat to potable water resources. However their toxicity and treatment options have not been throughly investigated, despite the significant growth of nanotechnology-based industries. The objective of this study is to provide fundamental information for the management of nanoparticles in water supply systems through extensive literature survey. More specifically, two types of nanoparticles are selected to be a potential problem for drinking water treatment. They are carbon nanoparticles such as carbon nanotube and fullerene, and metal nanoparticles including silver, gold, silica and titanium oxide. In this study, basic characteristics and toxicity of these nanoparticles were first investigated systematically. Their monitoring techniques and treatment efficiencies in conventional water treatment plants were also studied to examine our capability to mitigate the risk associated with nanoparticles. This study suggests that the technologies monitoring nanopartilces need to be greatly improved in water supply systems, and more advanced water treatment processes should be adopted for better control of these nanoparticles.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.586-592
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• 2009

The preparation of structures with nanosized arrays allows mimicking many different morphologies that exist in nature. In addition, polymer is considered as a material that can be easily applicable to the fabrication of nanostructures and can effectively exhibit nanosize effects since material, synthesis and processing cost is low, and many of polymer structures are well studied. Porous alumina template prepared by anodization of aluminum among nanofabrication methods is the one of promising routes that cost-effectively provides very regularly arrayed nanostructures. In this review, we describe the fabrication of the nanotemplate and template-based polymer nanostructures and their applications.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1871-1876
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• 2013

In this study, we developed and characterized the shielding properties of dose reduction fiber (DRF, Buffalo Co.) sheet during brain and chest CT examinations. The DRF sheet was composed of $1{\sim}500{\mu}m$ oxide Bismuth ($Bi_2O_3$) and 5 ~ 50 nm nano-barium sulfate ($BaSO_4$). Phantom and clinical studies were performed for characterization of the DRF shielding properties. In clinical study, we measured doses of eye, chest, abdomen and reproductive system of 60 patients in 3 hospitals during brain and chest CT examinations. We could determined the shielding effect of the DRF by comparing the doses when we used the DRF sheet or not. When we used the sheet during CT examination, the scattered dose were reduced about 20~50%. So, we suggest that the fiber should be used in radiological examinations for reducing patients doses.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.491-491
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• 2011

Transparent and flexible electronic devices that are light-weight, unbreakable, low power consumption, optically transparent, and mechanical flexible possibly have great potential in new applications of digital gadgets. Potential applications include transparent displays, heads-up display, sensor, and artificial skin. Recent reports on transparent and flexible field-effect transistors (tf-FETs) have focused on improving mechanical properties, optical transmittance, and performances. Most of tf-FET devices were fabricated with transparent oxide semiconductors which mechanical flexibility is limited. And, there have been no reports of transparent and flexible all-organic tf-FETs fabricated with organic semiconductor channel, gate dielectric, gate electrode, source/drain electrode, and encapsulation for sensor applications. We present the first demonstration of transparent, flexible all-organic sensor based on multifunctional organic FETs with organic semiconductor channel, gate dielectric, and electrodes having a capability of sensing infrared (IR) radiation and mechanical strain. The key component of our device design is to integrate the poly(vinylidene fluoride-triflouroethylene) (P(VDF-TrFE) co-polymer directly into transparent and flexible OFETs as a multi-functional dielectric layer, which has both piezoelectric and pyroelectric properties. The P(VDF-TrFE) co-polumer gate dielectric has a high sensitivity to the wavelength regime over 800 nm. In particular, wavelength variations of P(VDF-TrFE) molecules coincide with wavelength range of IR radiation from human body (7000 nm ~14000 nm) so that the devices are highly sensitive with IR radiation of human body. Devices were examined by measuring IR light response at different powers. After that, we continued to measure IR response under various bending radius. AC (alternating current) gate biasing method was used to separate the response of direct pyroelectric gate dielectric and other electrical parameters such as mobility, capacitance, and contact resistance. Experiment results demonstrate that the tf-OTFT with high sensitivity to IR radiation can be applied for IR sensors.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.487-487
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• 2011

Recently graphene has emerged as a fascinating 2D system in condensed-matter physics as well as a new material for the development of nanotechnology. The unusual electronic band structure of graphene allows it to exhibit a strong ambipolar electric field effect with high mobility. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ${\sim}60{\Omega}$/sq and ~85 % transmittance in the visible range (400?900 nm), the CVD-grown graphene electrodes have a higher/flatter transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition, for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10 ~ 15 nm in mean size were decorated along the surface of the graphene after 1.5 MeV-e-beam irradiation. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.388-388
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• 2011

Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. The physical properties of graphene depend directly on the thickness. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ~60 ${\Omega}/sq$ and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition,for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10~15 nm in mean size were decorated along the surface of the graphene after 1.0 MeV-e-beam irradiation. The fabrication high-performance TCF with optimized doping condition showed a sheet resistance of ~150 ${\Omega}/sq$ at 94% transmittance. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.