• 한국산학기술학회논문지
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• 제19권1호
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• pp.105-112
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• 2018

본 논문은 로이유리(Low emissivity glass) 표면에 증착되어 있는 금속박막의 전도 특성을 이용하여 발열유리(Heatable glass)를 제작하는 방법에 대해 제안한다. 로이유리의 발열량은 로이유리 표면저항에 의한 주울(Joule) 열에 의존하므로 소재의 표면저항을 측정함으로써 예측 및 설계가 가능하다. 본 연구에서는 저방사층이 11nm인 소프트로이유리 시료에 각 50mm 간격으로 은(Ag) 전극을 형성시키고, 4단자법으로 면저항을 측정하여 로이유리의 소비전력과 발열량을 예측한 후에, 제작 및 실험을 통해 발열성능을 확인하였다. 기존의 발열유리 제작방법은 크게 두 가지로 일반유리(Normal glass)에 니크롬(Nichrome) 열선을 삽입하는 방법과, 일반유리에 전도성 투명박막을 증착하는 방법이 있다. 니크롬 열선 삽입 방식은 발열성능은 우수하나 유리 고유의 투명성을 저해하고, 전도성 투명박막을 증착하는 방법은 투명성은 양호하나 공정이 복잡하여 실용성이 저하된다. 본 논문에서는 주로 건축물의 단열효과 향상을 위해 사용되는 로이유리를 이용하여 로이유리 전면에 코팅되어 있는 전도성 금속박막에 레이저 빔을 조사하여 원하는 발열성능을 가지는 발열유리를 제작하는 방법을 제안한다. 제안된 방법은 기존의 니크롬 열선을 삽입하는 방법에 비해 투명성이 양호하고, 전도성 투명박막을 증착하는 방법에 비해 제작과정이 보다 수월함을 확인하였다. 아울러, 레이저를 조사하여 로이유리의 표면 박막을 패터닝(Patterning) 하는 형태에 따른 발열특성의 비교와 로이유리에 적합한 레이저 출력조건을 제시하고자 한다.

• 분석과학
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• 제6권1호
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• pp.29-37
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• 1993

말단기에 페닐(B), 벤질(Bz), 피리딘(Py), 퀴놀린(Q) 또는 나프탈렌(Np), 그리고 에테르 사슬에 산소(O) 또는 황(S) 주개원자를 갖는 몇 가지 포단드를 합성하여 1가 양이온과의 결합특성을 NMR 적정법과 용매추출법으로 조사하였다. NMR 적정에 의하면 대부분의 포단드는 1가 양이온과 1:1 착물을 형성하며, 특히 은이온과의 상호작용에서 에테르 사슬의 황 원자는 안정도를 증가시키는 효과를 나타내었다. 또한 포단드를 이용하여 에테르 수용액층에서 클로로포름층으로 알칼리 금속, 은, 탈륨 및 암모늄 등의 피크린산 1가 양이온염을 추출하였다. 은이온에 대한 추출률은 $Q_2O_4$, $Q_2O_5$ 및 $BQO_5$와 같이 퀴놀린을 포함하는 포단드의 경우 각각 86.8, 86.6 및 48.0%였으나 나프탈렌을 갖는 $Np_2O_4$ 및 $Np_2O_5$에 의해서는 거의 추출되지 않았다. 한편, $Bz_2O_3S_2$(89.4%), $B_2O_2S_2$(76.8%), $B_2O_3S_2$(58.9%), $Py_2O_2S_2$(58.8%), $Py_2O_3S_2$(42.1%) 및 $B_2O_4S$(15.0%)의 경우, 황 원자와 벤질기를 갖는 $Bz_2O_3S_2$가 가장 큰 은이온 추출 선택성을 나타내었다. 이러한 결과는 HSAB 이론에 의한 황 원자와 은이온과의 강한 상호작용 뿐 아니라 페닐기 대신에 벤질기가 치환됨으로써 유연한 메틸렌기 공간에 의해 두 방향족 말단기 사이의 ${\pi}-{\pi}$ 스택킹 상호작용이 효과적으로 증가하기 때문이다. 추출계수는 안정도 및 추출률과 비슷한 경향성을 나타내었는데, 이로부터 추출계수에 주된 영향을 미치는 요인으로는 포단드의 구조와 밀접한 관계가 있는 안정도임을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.293.1-293.1
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• 2016

Various materials including conductive, dielectric, and semi-conductive materials, constitute suitable candidates for printed electronics. Metal nanoparticles (e.g. Ag, Cu, Ni, Au) are typically used in conductive ink. However, easily oxidized metals, such as Cu, must be processed at low temperatures and as such, photonic sintering has gained significant attention as a new low-temperature processing method. This method is based on the principle of selective heating of a strongly absorbent film, without light-source-induced damage to the transparent substrate. However, Cu nanoparticles used in inks are susceptible to the growth of a native copper-oxide layer on their surface. Copper-oxide-nanoparticle ink subjected to a reduction mechanism has therefore been introduced in an attempt to achieve long-term stability and reliability. In this work, a flash-light sintering process was used for the reduction of an inkjet-printed Cu(II)O thin film to a Cu film. Using a photographic lighting instrument, the intensity of the light (or intense pulse light) was controlled by the charged power (Ws). The resulting changes in the structure, as well as the optical and electrical properties of the light-irradiated Cu(II)O films, were investigated. A Cu thin film was obtained from Cu(II)O via photo-thermal reduction at 2500 Ws. More importantly, at one shot of 3000 Ws, a low sheet resistance value ($0.2527{\Omega}/sq.$) and a high resistivity (${\sim}5.05-6.32{\times}10^{-8}{\Omega}m$), which was ~3.0-3.8 times that of bulk Cu was achieved for the ~200-250-nm-thick film.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.225-225
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• 2013

Nanostructured noble metals have been attractive for their unusual optical properties and are widely utilized for various purposes. The optical properties mainly originating from collective electron oscillation can assist direct energy conversion via surface plasmon resonances. Here, we investigated the effect of surface plasmons of silver nanowires on the generation of hot electrons. It is reported that the surface plasmons of silver nanowires exhibit longitudinal and transverse modes, depending on the aspect ratio of the nanowires. In order to measure the hot electron flow through the metallic nanowires, chemically modified Au/TiO2 Schottky diodes were employed as the electric contact. The silver nanowires were deposited on a Au metal layer via the spray method to control uniformity and the amount of silver nanowire deposited. We measured the hot electron flow generated by photon absorption on the silver nanowires deposited on the Au/TiO2 Schottky diodes. The incident photon-to-current efficiency was measured a function of the photon energy, revealing two polarization modes of siliver nanowires: transverse and longitudinal modes. UV-Vis spectra exhibited two polarization modes, which are also consistent with the photocurrent measurements. Good correlation between the IPCE and UV-vis measurements suggests that hot electron measurement on nanowires on nanodiodes is a useful way to reveal the intrinsic properties of surface plasmons of nanowires.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.1.1-1.1
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• 2011

Printed electronics based on the direct writing of solution processable functional materials have been of paramount interest and importance. In this talk, the synthesis of printable inorganic functional materials (conductors and semiconductors) for thin-film transistors (TFTs) and photovoltaic devices, device fabrication based on a printing technique, and specific characteristics of devices are presented. For printable conductor materials, Ag ink is designed to achieve the long-term dispersion stability and good adhesion property on a glass substrate, and Cu ink is sophisticatedly formulated to endow the oxidation stability in air and even aqueous solvent system. The both inks were successfully printed onto either polymer or glass substrate, exhibiting the superior conductivity comparable to that of bulk one. In addition, the organic thin-film transistor based on the printed metal source/drain electrode exhibits the electrical performance comparable to that of a transistor based on a vacuum deposited Au electrode. For printable amorphous oxide semiconductors (AOSs), I introduce the noble ways to resolve the critical problems, a high processing temperature above $400^{\circ}C$ and low mobility of AOSs annealed at a low temperature below $400^{\circ}C$. The dependency of TFT performances on the chemical structure of AOSs is compared and contrasted to clarify which factor should be considered to realize the low temperature annealed, high performance AOSs. For photovoltaic application, CI(G)S nanoparticle ink for solution processable high performance solar cells is presented. By overcoming the critical drawbacks of conventional solution processed CI(G)S absorber layers, the device quality dense CI(G)S layer is obtained, affording 7.3% efficiency CI(G)S photovoltaic device.

• Carbon letters
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• 제8권4호
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• pp.274-279
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• 2007

In order to understand the breakthrough behaviour of iodine vapours on impregnated carbon systems, an active carbon, 80 CTC grade, $12{\times}30$ BSS particle size and $1104\;m^2/g$ surface area, was impregnated with metal salts such Cu, Cr, Ag, Mo and Zn, and an organic compound Triethylene diamine (TEDA) to prepare different carbon systems such as whetlerite, whetlerite/TEDA, whetlerite/KI/KOH and ASZMT. The prepared adsorbents along with active carbon were characterized for surface area and pore volume by $N_2$ adsorption at liquid nitrogen temperature. These carbon systems were compared for their CT (concentration X time) values at 12.73 to 53.05 cm/sec space velocities and 2 to 5 cm carbon column bed heights. The carbon column of 5.0 cm bed height and 1.0 cm diameter was found to be providing protection against iodine vapours up to 5.5 h at 3.712 mg/L iodine vapour concentration and 12.73 cm/sec space velocity. The study clearly indicated the adsorption capacities of carbon systems to be directly proportional to their surface area values. Dead layer with all the prepared carbon systems was found to be less than 2.0 cm indicating it to be minimum bed height to have protection against $I_2$ vapours. Effect of carbon bed height and flow rate was also studied. The active carbon showed maximum protection at all bed heights and flow rates in comparison to all other impregnated carbon systems, showing that only physical adsorption is responsible for the removal of iodine vapours.

• 마이크로전자및패키징학회지
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• 제28권3호
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• pp.17-24
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• 2021

페로브스카이트 태양전지는 용액공정으로 제작되어 공정 중 전구체 조성제어를 통해 밴드갭을 용이하게 조절할 수 있다. 탠덤 태양전지의 상부셀로 활용하여 실리콘 태양전지와 접합 시 30% 이상의 효율 달성이 가능하지만, 페로브스카이트 태양전지의 낮은 안정성이 상용화의 걸림돌로 작용하고 있다. 아이오딘 이온 및 전극 물질 확산이 주된 열화기구로 알려져 있어 장기 안정성을 확보하기 위해서는 이러한 이온 이동의 방지가 필요하다. 본 연구에서는 층간소재와 페로브스카이트 광활성층 사이의 이온이동에 의한 열화현상을 관찰하고, 이를 억제하기 위해 페로브스카이트 소재와 은전극 사이에 버퍼층을 도입하여 소자의 안정성을 확보하였다. 85℃에서 300시간 이상 보관 시 버퍼가 없는 소자는 페로브스카이트 층이 PbI₂ 및 델타상으로 변화하며 변색되었으며 AgI가 형성되는 것을 확인했다. LiF와 SnO₂ 버퍼 도입 시 이온이동 억제 효과를 통해 페로브스카이트 태양전지의 열안정성이 향상되었다. LiF버퍼층 적용 및 봉지를 한 소자는 85℃-85%RH damp heat 시험 200시간 후 효율감소가 발생하지 않았으며 추가로 AM 1.5G-1SUN 하에서 최대출력점을 추적하였을 때 200시간 후 초기 효율의 90% 이상 유지하는 것을 확인했다. 이 결과는 버퍼층 형성을 통한 층간 물질이동 억제가 장기안정성을 확보하기 위한 필요조건임을 보여준다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.304-304
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• 2006

기계적 에너지를 전지적 에너지로 변환하는 에너지 변환소자인 압전 세라믹스는 액츄에이터, 변압기, 초음파모터, 초음파 소자 및 각종 센서로 응용되고 있으며, 그 응용분야는 크게 종가하고 있다. 최근 이러한 에너지변환 소자를 앞으로 도래하는 유비쿼터스 무선 모바일 시대의 휴대용 전자제품, 즉 Wearable 컴퓨터, MP3, GSM, Bluetooth 등의 정보통신기기, Robotics, 항공우주, 자동차, 의료, 건축, MEMS 분야 등의 대체 에너지원으로 응용하기 위한 연구가 진행되고 있다. 특히 인간의 동작등과 같은 일상적인 동작(Typing, U. limbbing, Breathing, Walking 등)으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수가 있어서, 기존 이차전지, 연료전지를 대체 또는 보완 할 수 있는 방안도 검토되고 있다. 따라서 본 연구에서는 향후 응용 가능성이 큰 압전 발전 시스템을 제작하기 위해서 압전특성이 우수한 조성시스템 설계, 바이몰프 형태의 압전액츄에이터 제작, 그리고 발전시스템의 회로설계를 수행하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.156-156
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• 2000

Recently, the surface electronic states have attracted much attention since their standing wave patterns created around steps, defects, and adsorbates on noble metal surfaces such as Au(111), Ag(110), and Cu(111) were observed by scanning tunneling microscopy (STM). As a typical example, a striking circular pattern of "Quantum corral" observed by Crommie, Lutz, and Eigler, covers a number of text books of quantum mechanics, demonstrating a wavy nature of electrons. After the discoveries, similar standing waves patterns have been observed on other metal and demiconductor surfaces and even on a side polane of nano-tubes. With an expectation that the surface states could be utilized as one of ideal cases for studying two dimensionakl (sD) electronic system, various properties, such as mean free path / life time of the electronic states, have been characterized based on an analysis of standing wave patterns, . for the 2D electron system, electron density is one of the most importnat parameters which determines the properties on it. One advantage of conventional 2D electron system, such as the ones realized at AlGaAs/GaAs and SiO2/Si interfaces, is their controllability of the electrondensity. It can be changed and controlled by a factor of orders through an application of voltage on the gate electrode. On the other hand, changing the leectron density of the surface-state 2D electron system is not simple. On ewqy to change the electron density of the surface-state 2D electron system is not simple. One way to change the electron density is to deposit other elements on the system. it has been known that Pd(111) surface has unoccupied surface states whose energy level is just above Fermi level. Recently, we found that by depositing Pd on Cu(111) surface, occupied surface states of Cu(111) is lifted up, crossing at Fermi level around 2ML, and approaches to the intrinsic Pd surface states with a increase in thickness. Electron density occupied in the states is thus gradually reduced by Pd deposition. Park et al. also observed a change in Fermi wave number of the surface states of Cu(111) by deposition of Xe layer on it, which suggests another possible way of changing electron density. In this talk, after a brief review of recent progress in a study of standing weaves by STM, I will discuss about how the electron density can be changed and controlled and feasibility of using the surface states for a study of 2D electron system. One of the most important advantage of the surface-state 2D electron system is that one can directly and easily access to the system with a high spatial resolution by STM/AFM.y STM/AFM.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.188.1-188.1
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• 2015

For present investigation Fe/MgO/Fe/Co multilayer stack is grown on Si substrate using e-beam evaporation in ultrahigh vacuum. This stack is irradiated perpendicularly by 120 MeV $Ag^{8+}$ at different fluences ranging from $1{\times}10^{11}$ to $1{\times}10^{13}ions/cm^2$ in high vacuum using 15UD Pelletron Accelerator at Inter University Accelerator Centre, New Delhi. Magnetic measurements carried out on pre and post irradiated stacks show significant changes in the shape of perpendicular hysteresis which is relevant with previous observation of re-orientation of magnetic moment along the direction of ion trajectory. However increase in plane squareness may be due to the modification of interface structure of stacks. X-ray reflectivity measurements show onset of interface roughness and interface mixing. X-ray diffraction measurements carried out using synchrotron radiation shows amorphous nature of MgO and Co layer in the stack. Peak corresponding body centered Fe [JCPDS-06-0696] is observed in X-ray diffraction pattern of pre and post irradiated stacks. Peak broadening shows granular nature of Fe layer. Estimated crystallite size is $22{\pm}1nm$ for pre-irradiated stack. Crystallite size first increases with irradiation then decreases. Structural quality of these stacks was further studied using transmission electron microscopic measurements. Thickness from these measurements are 54, 36, 23, 58 and 3 nm respectively for MgO, Fe, MgO, Fe+Co and Au layers in the stack. These measurements envisage poor crystallinity of different layers. Interfaces are not clear which indicate mixing at interface. With increase fluence mixing and diffusion was increased in the stack. X-ray absorption spectroscopic measurements carried out on these stacks show changes of Fe valence state after irradiation along with change of O(2p)-metal (3d) hybridized state. Valence state change predicts oxide formation at interface which causes enhanced in-plane magnetization.