TaNx film is grown by plasma enhanced atomic layer deposition (PEALD) using t-butylimido tris(dimethylamido) tantalum as a metalorganic source with various reactive gas species, such as N2+H2 mixed gas, NH3, and H2. Although the pulse sequence and duration are the same, aspects of the film growth rate, microstructure, crystallinity, and electrical resistivity are quite different according to the reactive gas. Crystallized and relatively conductive film with a higher growth rate is acquired using NH3 as a reactive gas while amorphous and resistive film with a lower growth rate is achieved using N2+H2 mixed gas. To examine the relationship between the chemical properties and resistivity of the film, X-ray photoelectron spectroscopy (XPS) is conducted on the ALD-grown TaNx film with N2+H2 mixed gas, NH3, and H2. For a comparison, reactive sputter-grown TaNx film with N2 is also studied. The results reveal that ALD-grown TaNx films with NH3 and H2 include a metallic Ta-N bond, which results in the film’s higher conductivity. Meanwhile, ALD-grown TaNx film with a N2+H2 mixed gas or sputtergrown TaNx film with N2 gas mainly contains a semiconducting Ta3N5 bond. Such a different portion of Ta-N and Ta3N5 bond determins the resistivity of the film. Reaction mechanisms are considered by means of the chemistry of the Ta precursor and reactive gas species.

We report on the fabrication and photoelectrochemical(PEC) properties of a Cu2O thin film/ZnO nanorod array oxide p-n heterojunction structure with ZnO nanorods embedded in Cu2O thin film as an efficient photoelectrode for solardriven water splitting. A vertically oriented n-type ZnO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method and then a p-type Cu2O thin film was directly electrodeposited onto the vertically oriented ZnO nanorods array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were characterized using X-ray diffraction and scanning electron microscopy as well as Raman scattering. The PEC properties of the fabricated Cu2O/ZnO p-n heterojunction photoelectrode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the Cu2O/ZnO photoelectrode was found to exhibit a negligible dark current and high photocurrent density, e.g., 0.77 mA/cm2 at 0.5 V vs Hg/HgCl2 in a 1 mM Na2SO4 electrolyte, revealing an effective operation of the oxide heterostructure. In particular, a significant PEC performance was observed even at an applied bias of 0 V vs Hg/ HgCl2, which made the device self-powered. The observed PEC performance was attributed to some synergistic effect of the p-n bilayer heterostructure on the formation of a built-in potential, including the light absorption and separation processes of photoinduced charge carriers.

In order to increase the efficiency of the sputtering method widely used in thin film fabrication, a dc sputtering apparatus which supplies both high frequency and magnetic field from the outside was fabricated, and cobalt thin film was fabricated using this apparatus. The apparatus can independently control the applied voltage, the target-substrate distance, and the target current, which are important parameters in the sputtering method, so that a stable glow discharge is obtained even at a low gas pressure of 10−3 Torr. The fabrication conditions using the sputtering method were mainly performed in Ar+O2 mixed gas containing about 0.6% oxygen gas under various Ar gas pressures of 1 to 30 mTorr. The microstructure of Co thin films deposited using this apparatus was examined by electron diffraction pattern and X-ray techniques. The magnetic properties were investigated by measuring the magnetization curves. The microstructure and magnetic properties of Co thin films depend on the discharge gas pressure. The thin film fabricated at high gas pressure showed a columnar structure containing a large amount of the third phase in the boundary region and the thin film formed at low gas pressure showed little or no columnar structure. The coercivity in the plane was slightly larger than that in the latter case.

Li-incorporated ZnO thin films were deposited by using ultrasonic-assisted spray pyrolysis deposition (SPD) system. To investigate the effect of Li-incorporation on the performance of ZnO thin films, the structural, electrical, and optical properites of the ZnO thin films were analyzed by means of X-ray diffraction (XRD), field-emssion scanning electron microscopy (FE-SEM), Hall effect measurement, and UV-Vis spectrophotometry with variation of the Li concentraion in the ZnO sources. Without incorporation of Li element, the ZnO surface showed large spiral domains. As the Li content increases, the size of spiral domains decreased gradually, and finally formed mixed small grain and one-dimensional nanorod-like structures on the surface. This morphological evolution was explained based on an anti-surfactant effect of Li atoms on the ZnO growth surface. In addition, the Li-incorporation changed the optical and electrical properties of the ZnO thin films by modifying the crystalline defect structures by doping effects.

정삼투법을 이용한 해수담수화는 역삼투 공정에 비해 에너지 절감이 가능하여 해수담수화 차세대 기술로 주목받 고 있다. 막을 기반으로 하는 수처리 분야에서 분리 성능을 향상시키고 새로운 기능을 부여하기 위해, 고분자 매트릭스에 필 러인 나노물질을 삽입하는 박막 나노복합체 분리막(thin film nanocomposite, TFN) 개발에 대한 연구가 요구되고 있다. 본 연구에서는 딥 코팅(dip coating) 방법을 기반으로 한 다층박막적층법(Layer-by-layer, LBL)을 이용하여 산화그래핀(graphene oxide, GO)의 나노 적층구조를 제어하여, 정삼투 공정에서의 높은 안정성 및 높은 수투과도 및 염 제거, 낮은 염 역확산을 갖는 그래핀 나노복합체 분리막을 개발하고자 하였다. 정삼투 공정의 성능 향상을 위한 산화그래핀의 환원 반응시간과 LBL 딥 코팅 적층 수의 최적화를 통해, 수투과도 2.51 LMH/bar, 물분자 선택성 8.3 L/g, 염 제거율 99.5%를 갖는 나노복합체 분리막 을 개발하였다. 이는 상용화된 CTA FO 분리막보다 수투과도는 10배, 물분자 선택성은 4배 높게 향상되었으며, 염 제거율은 비슷한 수준으로 나타났다.

We report on the efficient detection of NO gas by an all-oxide semiconductor p-n heterojunction diode structure comprised of n-type zinc oxide (ZnO) nanorods embedded in p-type copper oxide (CuO) thin film. The CuO thin film/ZnO nanorod heterostructure was fabricated by directly sputtering CuO thin film onto a vertically aligned ZnO nanorod array synthesized via a hydrothemal method. The transport behavior and NO gas sensing properties of the fabricated CuO thin film/ ZnO nanorod heterostructure were charcterized and revealed that the oxide semiconductor heterojunction exhibited a definite rectifying diode-like behavior at various temperatures ranging from room temperature to 250 oC. The NO gas sensing experiment indicated that the CuO thin film/ZnO nanorod heterostructure had a good sensing performance for the efficient detection of NO gas in the range of 2-14 ppm under the conditions of an applied bias of 2 V and a comparatively low operating temperature of 150 oC. The NO gas sensing process in the CuO/ZnO p-n heterostructure is discussed in terms of the electronic band structure.

HiPIMS(High Power Impulse Magnetron Sputtering)를 이용하여 탄소 박막을 증착하였다. 파워, 압력, 바이어스 전압, duty cycle에 따른 탄소 박막의 특성과 미세조직을 조사하였다. HiPIMS 파워가 증가할수록 증착 두께는 증가하였으며 표면이 거칠어지는 경향을 보였다. 압력의 증가 또한 표면이 거칠어지는 경향을 보였으나 증착 두께는 압력에 비례하지 않았다. 바이어스 전압이 증가함에 따라 조도가 나빠졌고 증착 두께는 증가하다가 임계 바이어스 전압부터는 감소하는 경향을 보였다. 듀티 사이클의 변화는 아크 발생과 같은 문제를 유발했으며 이는 챔버 구조나 타겟의 크기 등에 영향을 받는다. XPS로 sp²/sp³ 분율을 확인하였으며 sp²/sp³ 분율이 DC 스퍼터링의 경우보다 HiPIMS의 경우가 더 큰 것을 확인하였다.

본 연구에서는 0.5, 1.0, 1.5 wt%의 TiO2를 함유하는 인듐-티타늄 수산화물을 졸 및 염기 첨가에 의해 얻었고, 200oC와 500oC에서 겔화 과정을 통해 ITiO(Indium Titanate Oxide)를 얻었다. 200oC에서 겔화 과정 후 얻어지는 ITiO 입자가 작아서 조밀성이 있는 ITiO 타겟을 제조하였다. 0.5, 1.0, 1.5 wt%의 TiO2를 함유하는 ITiO 타겟을 스퍼터링하여 ITiO 박막을 유리판위에 제작하여 비저항, 전하 이동도, 캐리어 농도를 조사하였다. 이들 박막 중에서 산소 조성이 0.4 %인 조건에서 0.5 wt% 중량% TiO2를 함유하는 ITiO 타겟으로부터 제작된 ITiO 박막이 가장 낮은 비저항, 가장 큰 전하이동도 및 가장 낮은 캐리어 농도를 보임을 알 수 있었고, 얻어진 ITiO 박막의 광투과율을 측정하여 적외선 영역에서 광투과율이 ITO(Indium Tin Oxide) 박막에 비해 현저히 증가함을 발견하였다.

계면중합법은 혼합되지 않은 두 용액에 용해되어 있는 반응성 단량체들이 계면에서 중합되는 기술로 다양한 분야 에 응용되고 있다. 이 중, 수처리 분리막의 경우 m-phenylene diamine과 Trimesoyl chloride를 반응물로 사용하고 있다. 분리 막의 성능은 다양한 중합 성능에 의해 영향을 받고 있으며, 본 연구에서는 유기 용액의 퍼짐 속도가 어떻게 분리막 표면 및 구조에 영향을 주는지를 주사전자현미경을 통해 고찰하였다. 퍼짐 속도는 7.6과 25 mm/sec로 조절하였으며, 유기상 용액은 1~3방울까지 조절하였다. 관찰된 결과는 퍼짐 속도가 7.6 mm/sec에서는 한 방울 떨어트릴 경우, 25 mm/sec에서는 두 방울 떨어트릴 경우 폴리아마이드 막에 균열을 발견할 수 없었다. 반면 나머지 경우에 모두 균열이 발생하였다. 따라서, 초기 유기 용액의 퍼짐 속도는 폴리아마이드 분리막의 성능에 영향을 줄 것으로 관찰되었다.

In this study, we investigated the overpotential of precipitation related to the catalytic activity of electrodes on the initial process of electrodeposition of Co and Co-Ni alloys on polycrystalline Cu substrates. In the case of Co electrodeposition, the surface morphology and the magnetic property change depending on the film thickness, and the relationship with the electrode potential fluctuation was shown. Initially, the deposition potential(−170 mV) of the Cu electrode as a substrate was shown, the electrode potential(Edep) at the Ton of electrodeposition and the deposition potential(−600 mV) of the surface of the electrodeposited Co film after Toff and when the pulse current was completed were shown. No significant change in the electrode potential value was observed when the pulse current was energized. However, in a range of number of pulses up to 5, there was a small fluctuation in the values of Edep and Eimm. In addition, in the Co-Ni alloy electrodeposition, the deposition potential(−280 mV) of the Cu electrode as the substrate exhibited the deposition potential(−615 mV) of the electrodeposited Co-Ni alloy after pulsed current application, the Edep of electrodeposition at the Ton of each pulse and the Eimm at the Toff varied greatly each time the pulse current was applied. From 20 % to less than 90% of the Co content of the thin film was continuously changed, and the value was constant at a pulse number of 100 or more. In any case, it was found that the shape of the substrate had a great influence.

20 μm의 얇은 폴리에스터(polyester) 부직포 상에 폴리술(polysulfone) 고분자 지지체를 제조하였다. 폴리술폰 표면에 3-aminopropyldimethyl silane을 sol-gel 중합함으로써 폴리실록산 지지체를 제조한 후 MPD 수용액과 TMC 유 기용액의 계면 중합을 실시를 통하여 정삼투 복합박막을 얻었다. FE-SEM/EDX 분석을 통하여 폴리실록산이 표면에 한하여 분포됨을 확인하였다. 1 M NaCl 유도용액/순수 인입용액 하에서의 FO-mode 유량이 146 - 209 LMH로 향상되 었으며 RSF값은 0.42 - 16.3 GMH로 유지함을 확인할 수 있었다.

We investigated the effect of ZnO buffer layer on the formation of ZnO thin film by ultrasonic assisted spray pyrolysis deposition. ZnO buffer layer was formed by wet solution method, which was repeated several times. Structural and optical properties of the ZnO thin films deposited on the ZnO buffer layers with various cycles and at various temperatures were investigated by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence spectrum analysis. The structural investigations showed that three-dimensional island shaped ZnO was formed on the bare Si substrate without buffer layers, while two-dimensional ZnO thin film was deposited on the ZnO buffer layers. In addition, structural and optical investigations showed that the crystalline quality of ZnO thin film was improved by introducing the buffer layers. This improvement was attributed to the modulation of the surface energy of the Si surface by the ZnO buffer layer, which finally resulted in a modification of the growth mode from three to two-dimensional.

In this study, we investigate the effect of the diffusion barrier and substrate temperature on the length of carbon nanotubes. For synthesizing vertically aligned carbon nanotubes, thermal chemical vapor deposition is used and a substrate with a catalytic layer and a buffer layer is prepared using an e-beam evaporator. The length of the carbon nanotubes synthesized on the catalytic layer/diffusion barrier on the silicon substrate is longer than that without a diffusion barrier because the diffusion barrier prevents generation of silicon carbide from the diffusion of carbon atoms into the silicon substrate. The deposition temperature of the catalyst and alumina are varied from room temperature to 150°C, 200°C, and 250°C. On increasing the substrate temperature on depositing the buffer layer on the silicon substrate, shorter carbon nanotubes are obtained owing to the increased bonding force between the buffer layer and silicon substrate. The reason why different lengths of carbon nanotubes are obtained is that the higher bonding force between the buffer layer and the substrate layer prevents uniformity of catalytic islands for synthesizing carbon nanotubes.

The effects of electron beam(EB) irradiation on the electrical and optical properties of InGaZnO(IGZO) thin films fabricated using a sol-gel process were investigated. As the EB dose increased, the electrical characteristic of the IGZO TFTs changed from semiconductor to conductor, and the threshold voltage values shifted to the negative direction. X-ray photoelectron spectroscopy analysis of the O 1s core level showed that the relative area of oxygen vacancies increased from 14.68 to 19.08 % as the EB dose increased from 0 to 1.5 × 1016 electrons/cm2. In addition, spectroscopic ellipsometer analysis showed that the optical band gap varied from 3.39 to 3.46 eV with increasing EB dose. From the result of band alignment, it was confirmed that the Fermi level(EF) of the sample irradiated with 1.5 × 1016 electrons/cm2 was located at the closest position to the conduction band minimum(CBM) due to the increase of electron carrier concentration

Aluminum-oxide(Al2O3) thin films were deposited by electron cyclotron resonance plasma-enhanced atomic layer deposition at room temperature using trimethylaluminum(TMA) as the Al source and O2 plasma as the oxidant. In order to compare our results with those obtained using the conventional thermal ALD method, Al2O3 films were also deposited with TMA and H2O as reactants at 280 oC. The chemical composition and microstructure of the as-deposited Al2O3 films were characterized by X-ray diffraction(XRD), X-ray photo-electric spectroscopy(XPS), atomic force microscopy(AFM) and transmission electron microscopy(TEM). Optical properties of the Al2O3 films were characterized using UV-vis and ellipsometry measurements. Electrical properties were characterized by capacitance-frequency and current-voltage measurements. Using the ECR method, a growth rate of 0.18 nm/cycle was achieved, which is much higher than the growth rate of 0.14 nm/cycle obtained using thermal ALD. Excellent dielectric and insulating properties were demonstrated for both Al2O3 films.

Porous polytetrafluoroethylene (PTFE) thin films are fabricated by spin-coating using a dispersion solution containing PTFE powders, and their crystalline properties are investigated after thermal annealing at various temperatures ranging from 300 to 500°C. Before thermal annealing, the film is densely packed and consists of many granular particles 200-300 nm in diameter. However, after thermal annealing, the film contains many voids and fibrous grains on the surface. In addition, the film thickness decreases after thermal annealing owing to evaporation of the surfactant, binder, and solvent composing the PTFE dispersion solution. The film thickness is systematically controlled from 2 to 6.5 μm by decreasing the spin speed from 1,500 to 500 rpm. A triboelectric nanogenerator is fabricated by spin-coating PTFE thin films onto polished Cu foils, where they act as an active layer to convert mechanical energy to electrical energy. A triboelectric nanogenerator consisting of a PTFE layer and Al metal foil pair shows typical output characteristics, exhibiting positive and negative peaks during applied strain and relief cycles due to charging and discharging of electrical charge carriers. Further, the voltage and current outputs increase with increasing strain cycle owing to accumulation of electrical charge carriers during charge-discharge.

목적: ITO 박막과 발수 박막의 두께에 따른 안경렌즈 투과율 변화를 관찰하고자 한다. 방법: Electron beam evaporation 와 dipping장비로 ITO 코팅, 발수 코팅, SiO2, ZrO2, 하드 코팅 막 을 제작하고 분광광도계와 ellipsomter를 이용하여 파장에 따른 광학상수를 구했다. 이러한 데이터를 이용 하여 Macleod 프로그램으로 ITO 박막과 발수 박막의 두께에 따른 안경렌즈 투과율의 변화를 관찰하였다. 박막설계는 [air / repellent film / ITO / SiO2-ZrO2-SiO2-ZrO2 / AR coating / hard coating(1.553) / lens(1.56)] 와 같다. 결과: ITO 박막과 발수 박막이 없을 시 최적 투과율은 400nm에서 700nm 까지의 평균 투과율은 약 99.5%이다. 안경렌즈 전 후면에서의 반사율이 비슷하므로 안경렌즈 전체 투과율은 약 99%이다. 발수 박막 의 두께를 고정시키고 ITO 박막의 두께를 증가시키면 가시광선의 단파장 영역의 투과율이 장파장에 비해 많 이 감소된다. ITO 박막을 고정시키고 발수 박막의 두께를 증가시킬 경우 장파장의 투과율이 감소하고 단파 장의 투과율은 발수 박막의 두께가 50nm 까지 감소하다가 그 이후에서는 투과율이 증가한다. 결론: ITO 박막의 두께를 증가시키면 가시광선의 단파장 영역의 투과율이 장파장에 비해 많이 떨어지고, 발수 박막의 두께를 증가시킬 경우 장파장의 투과율이 감소하고 단파장의 투과율은 발수 박막의 두께가 50nm 까지 감소하다가 그 이후에서는 투과율이 증가한다.

In this study, we present a unique surface modification method for a water desalination membrane to control the surface fouling via titanium dioxide (TiO2) nanopillar pattern imprinting. The patterned membranes showed significantly improved fouling resistance for both organic protein and bacterial foulants compared to the nonpatterned membranes. The hydrophilicity of TiO2 used as a pattern material affects the improvement of chemical antifouling resistance of the membrane. Fouling behavior was also interpreted in terms of the topographical effect depending on the relative size of foulants to the pattern dimension. Moreover, the computational fluid dynamics simulation intimates that the overall and local shear stress enhancement on the patterned surface could affect the foulant deposition behavior on the membrane.

We report on a unique fabrication technique, DSC for high performance PA TFC RO membranes. DSC allows the simultaneous and continuous spreading of two reactive monomer solutions to create an unsupported PA layer, which is then adhered onto a porous support to form a membrane. DSC facilitates the characterization of the PA layer structure by easily isolating it. The DSC-PA layer exhibits a thinner and smoother structure with a more wettable and less negatively charged surface than one prepared via conventional interfacial polymerization (IP). DSC enables the formation of an extremely thin (~9 nm) and dense PA layer using a very low MPD concentration, which is not feasible by conventional IP. Importantly, the DSC-assembled membrane shows the excellent water flux and NaCl rejection, exceeding both the IP control and commercial RO membranes.

A salinity gradient power (SGP) system holds a great potential to generate continuous and clean electricity for 24 hours. Recently, incorporating with seawater reverse osmosis, SGP has been recognized as a alternative to solve the brine issue as well as energy saving. For commercialization, many scientists would sympathize that one of main hurdles is the limited performance of each membrane to extract the high power. In case of pressure retarded osmosis (PRO) closer to commercialization, the membrane must have the high water permeability and salt rejection. There are two type of modules; hollow fiber membranes and spiral type. Toray Chem. (Korea) already shows that 4th generation PRO module, but there is no still large size PRO hollow fiber modules. Therefore, this study presents 2 and 3 inch size of PRO hollow fiber membrane prepared by inside interfacial polymerization techniques.