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Due to the reduced thickness of thin films formed via atomic layer deposition, analyzing their true mechanical properties is difficult. To overcome this drawback, tensile tests on free-standing alumina thin films floating on water were conducted to measure their mechanical properties. Tensile tests on alumina thin films formed at different deposition temperatures were also conducted; the results indicated that higher Young's modulus and the strength were obtained from thin films formed at higher deposition temperatures. Factors responsible for the variations in mechanical properties were investigated through analyses of the structure, density, and composition of the films.

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This study evaluates the performance and stability of Pt cathodes, which are treated by infiltrating cerium oxide (CeOx) onto their surfaces, in polymer electrolyte membrane fuel cells. The concentration of CeOx on the surface of Pt is adjusted by varying the concentration of the cerium precursor in the infiltration solution. The peak power density of the cell using the Pt cathode featuring the optimal amount of infiltrated CeOx is as high as 400 mW cm−2 at 70 °C, which is approximately 40% higher than that of the cell using the untreated Pt cathode under identical test conditions. Electrochemical impedance analysis confirms that this increase in peak power density is clearly attributed to the decrease in cathodic polarization impedance, which implies that the CeOx deposited on the surface of Pt enhances the catalytic performance of Pt. The infiltration of CeOx on the surface of Pt is also confirmed to be truly effective for improving the stability of Pt. Accelerated degradation tests demonstrate that the degradation rates of the cells using CeOx-Pt cathodes are significantly lower than that of the cell using the untreated Pt cathode because of the preservation of electrochemically active sites, as revealed by cyclic voltammetry.

The semiconductor etching process, which is the most important part of the semiconductor manufacturing process, requires higher sophistication as 10 nm semiconductors are mass produced. Etching methods utilizing plasma are getting increasingly popular with the miniaturization of the etching process. As the process performance depends on the state of the plasma variables, such as electron density, it is essential to measure and control these variables in real time. Moreover, to control the plasma-based system, the sensitive and time-varying characteristics of plasma should be considered. This paper proposes a self-tuning adaptive model predictive controller that can effectively perform electron density control. As a first step, an integral squared error-based Bayesian optimization is used to tune the model predictive controller, and its performance is verified on a drift-free Ar plasma system. The self-tuning adaptive model predictive controller is constructed by combining a recursive model parameter estimator with a model predictive controller. The recursive model parameter estimator is designed using a recursive least squares algorithm with Kalman filter interpretation. The effectiveness of the proposed controller is verified through control simulations and a set-point tracking experiment on the electron density with artificial drift in real time. The experimental results show that the performance of the proposed controller is 21% better than that of the conventional model predictive controller. We expect that this result will make a significant contribution to control processes utilizing plasma.

Recently, atomic layer deposition (ALD) has drawn much attention as a suitable tool for fabrication and engineering of high performance fuel cell catalysts and electrodes. Intrinsic merits of ALD enable synthesis of conformal and uniform film even at a sub-nm scale with excellent stoichiometry control and reproducibility. Leveraging the unique characteristics, ALD has proven its promising potential as a solution to achieve two major challenges of solid oxide fuel cell research: sluggish kinetics at low operational temperatures and long-term stability. In this review, recent efforts to address the challenges by the use of ALD-based functionalization of surfaces and interfaces of cell components are discussed.

In this study, wind-battery hybrid power systems are designed, evaluated, and optimized for regular supply of electrical power at a designated minimum load level with no shortage. Our simulation uses lead-acid batteries and vanadium redox flow batteries (VRBs) for storage, and utilizes hourly wind speed data measured in 2012 at Mt. Taegi in South Korea. Twenty Vestas V80 wind turbines, each rated at 2 MW, are used as power generators, on the basis of an actual wind turbine project recently installed at Mt. Taegi. Sale to the main grid of electricity generated in excess of the minimum load offset the initial capital costs for installation of the wind turbines and batteries. Results show that the optimized wind-VRB hybrid system can supply more than 9 MW of regular electrical power at no cost. Even higher levels of production are profitable with sale of the wind-generated electricity directly to a demand site at a price greater than the price of sales to the main grid. A reduction in the VRB electrolyte costs and an increase in carbon taxes can also increase profitability.

The mechanical properties of free-standing atomic layer-deposited alumina thin films were evaluated in this study. Stress-strain curves were obtained by measuring alumina films floating on the water surface. The Young's modulus, strength, and elongation of the free-standing films were analyzed at varying deposition temperatures of 80-200°C. The results show that the mechanical properties improve with increasing temperature. The microstructures of the films were examined to explain the change of the mechanical properties depending on the deposition conditions. Finally, the underlying causes of the differences in the mechanical properties were analyzed by evaluating the chemical composition of the thin films.

In this study, the performance of the cathode catalyst of polymer electrolyte membrane fuel cells is improved by the atomic layer deposition (ALD) of a protective layer. An atomic layer-scale zirconia protective layer is coated on the platinum catalyst for surface treatment. The results indicate that a very thin layer deposition with two ALD cycles or less is required to minimize the deterioration of the activity of the catalyst. Further, it is also confirmed that the catalyst aggregation can be effectively suppressed by its encapsulation with the protective layer through several ALD cycles from the analysis of the electrochemical surface area by cyclic voltammetry and the change in the catalyst particle size. According to the results, even two ALD cycles, which provide less than one atom layer, has decreased the deterioration rate to one-fourth of that of the untreated catalyst, with a minor decrease in the fuel cell power. In addition, the I–V data and impedance spectroscopy confirms that the overall stability of the membrane electrode assembly is improved by the ALD treatment. Thus, the ALD of a protective layer is considered to be a very promising strategy to improve the stability and performance of fuel cell catalysts.

With the advent of more than Moore’s law era, control of plasma etch process is expected to become inevitable. Given that highly complex plasma is a medium of etch processes, plasma parameters are key factors to be controlled. In addition, highly interactive plasma characteristics require multivariate control schemes. In this paper, we design a multi-loop controller which controls effective plasma parameters in Ar plasma conditions. The effective plasma parameters obtained by optical emission spectroscopy are paired with plasma reactor instrumental variables through relative gain array and singular value decomposition. Each single input-single output (SISO) system based on the pairing result shows successful disturbance rejection performance but interactions between SISO controllers occur. In order to handle the interactions, 2 × 2 multiple input-multiple output (MIMO) controllers with and without decouplers are simulated to track set point change. Based on the simulations, a MIMO controller with decouplers is implemented in a capacitively coupled plasma reactor and show feasible control performance without interaction. Hopefully, the results introduced in this paper contribute to making progress in plasma parameter control.

This study reports on protonic ceramic fuel cells (PCFCs) that exhibit enhanced performance after the addition of palladium (Pd) interlayers at the cathode–electrode interface. The Pd interlayer is deposited by sputtering on the BaZr0.2Ce0.6Y0.1Yb0.1O3-δ (BZCYYb) electrolyte surface, followed by the inkjet printing of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) and sintering. The proposed method successfully has produced a Pd layer that was well integrated between the BZCYYb and PBSCF layers, with no undesired reactions or phase formation. The Pd layer is diffused along the inner surface of the porous PBSCF cathode with the desired gradient composition. In our experiment, the fuel cell power is enhanced by up to 60% compared to the untreated PCFCs. In the former, the peak power density of the optimal cell is 420 mW cm−2, while that of the untreated sample is 260 mW cm−2 at 500 °C. The long-term stability of the Pd interlayer is confirmed during cell operation. The impedance analysis has revealed that the presence of the Pd significantly enhances the current collection and reduces the polarization impedance at the cathode–electrolyte interface, especially at low temperatures. These results indicate that the proposed method is promising for the fabrication of high-performance and robust PCFCs.

In this study, we investigate the accuracy of wind-speed prediction at a designated target site using wind-speed data from reference stations that employ an ANN (artificial neural network). The reference and target sites fall into three geographical categories: plains, coast, and mountains of South Korea. Accurate wind-speed predictions are calculated by means of a correlation coefficient between the actual and simulated wind-speed data obtained by ANN. We investigate the effect of the geological characteristics of each category and the distance between reference and target sites on the accuracy of wind-speed prediction using ANN.

In recent years, plasma etching process has been considered important because it is one of the most critical processes in semiconductor manufacturing. Numerous research results have been presented in relation to the plasma etch processes, especially plasma parameters control. Although the above results are expected to bring about positive effects in various fields, they do not consider the variability of the system. In this paper, we performed the recursive model estimation of which the model structure is ARX considering the time delay. The recursive algorithm contains the Kalman filter interpretation to the model parameters. we have confirmed that the system model updated in real-time by our recursive model estimation algorithm continuously calculates the model parameters that predict the output variable precisely. Through these results, we expect the better performance of MPC control using the recursive model estimation

In recent years, the development of AI has been accelerated so that the semiconductor manufacturing process has also been regarded as a very important issue. Many research results related to the plasma etch process which is one of the most important processes in the semiconductor manufacturing process have been presented in various forms. Recently, our research group has also presented a case of successful real-time multivariable control of plasma parameters based on optical emission spectroscopy. Although the above results are expected to bring about positive effects in various fields, they do not consider the variability of the system. Plasma related systems are so sensitive that online system identification is inevitable. In this paper, we performed the online system identification of the system composed of the plasma parameter through recursive parameter estimation method. Through the recursive algorithm using forgetting factor and input and output information which was gathered in real-time, we detected that the system was changing in real-time and updated the model parameters. We expect the results introduced in this paper contributes not only to the semiconductor manufacturing process but also to all the processes using plasma.

Many automakers have recently developed and commercialized electric vehicles that operate on polymer electrolyte membrane fuel cells (PEMFCs). The most important component in PEMFCs is the platinum catalyst. Fuel cell electric vehicles are expected to be particularly useful for heavy-duty cars including buses and trucks that operate at relatively high power for a relatively long-term per charge. Under these operating conditions, it is important to minimize aggregation of platinum (Pt) catalysts that tend to agglomerate in long-term high current (or high power) conditions. In this study, we propose the surface coating of zirconia (ZrO2) using atomic layer deposition (ALD) to prevent the aggregation of fuel cell catalysts. ALD is the most advanced technology for thin film deposition because it can control thickness and composition at the atomic scale. Another advantage of ALD is conformal coating along the surface of complex 3D features. With these unique properties, ALD has successfully demonstrated uniform surface coatings on nanoparticles. One cycle of ALD is generally less than 0.1 nm in many cases, which can in principle form a porous film. We selected ZrO2 as a coating material because of its high thermal and phase stability. As a result, we have succeeded in uniformly depositing ALD ZrO2 as a porous film on the surface of the nano-size metal catalyst, and confirmed that it is truly effective in preventing agglomeration of catalysts in a long-term fuel cell operation.

Organic/inorganic hybrid gels were directly prepared by polymerization on the peroxide surface of silica particles where the particle surface was irradiated by a 60Co γ-ray. These hydrogels have no residues of initiators or cross-linkers, so they can be used in biocompatible gel applications. Wide Raman spectroscopy was used to verify the interaction between the particles and poly(acrylic acid) (PAA). We observed that covalent bonds existing between the peroxide particles and acrylic acid, and the hydrogen bonds between the acrylic acids. For these studies, we prepared hydrogels by varying the particles’ concentration and the size of the silica particles to classify the number of reaction sites, which are the dominant factor for the chemical reaction between the silica particles and PAA. Open image in new window

Direct Methanol Solid Oxide Fuel Cell (DMSOFCs) has been drawn comparable attentions in fuel cell society for its fuel flexibility and high energy density of methanol compared to that of hydrogen. However, carbon coking and carbon monoxide poisoning occur due to usage of methanol as fuel, which hinder electrode kinetics and eventually cause performance degradation. Therefore, demand of high performance catalyst with excellent stability has been risen for the widespread usage of DMSOFC. To these days, bimetallic Pt-Ru is known as the best DMSOFC catalyst for its superior methanol oxidation capability. However, high scarcity of Pt and Ru hinders the widespread commercialization of DMSOFC for its expensive price. Recently, Ni has been considered as promising alternative for Pt-Ru. Price of Ni is far lower than that of Pt or Ru, and Ni has respectable methanol oxidation ability. During electrochemical oxidation of methanol, however, carbon tends to deposited on the surface of Ni, which leads performance and stability degradation of Ni catalyst. In this study, we deposited the palladium nanoparticles on the surface of Ni in order to obtain bimetallic Pd/Ni catalyst for DMSOFC application. Pd nanoparticles were deposited by DC magnetron sputtering and atomic layer deposition. DMSOFC with Pd/Ni catalyst were analyzed by current-voltage measurement and electrochemical impedance spectroscopy at the temperature range of 300 - 450 ºC. Pd/Ni catalyst showed enhanced performance and stability compared to bare Ni catalyst. Detailed analysis of experiment will be discussed in the presentation.

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) has been drown much attentions due to its high energy density, pollution-free electricity generation. Because of its versatile advantages, PEMFCs are considered as next-generation transportation system, which is used for power system of fuel cell electronic vehicle (FCEV). However, the usage of Pt catalyst hinders the widespread application of PEMFC because of high price of Pt. In order to utilize Pt in cost-effective way, various researches have been conducted to maximize the performance and long-term stability of Pt catalyst. Recently, many researches of Pt-metal oxide/C catalyst in PEMFCs have been investigated due to improvement of adsorption characteristics for oxygen at the surface of Pt by adding metal oxide. Especially, Cerium oxide has superior oxygen storage capability originated from easy redox between Ce3+ and Ce4+. Also, Pt-CeOx interact regions increase active sites where oxygen and Pt catalyst could meet together. In this study, we treated PEMFC cathode by cerium oxide with infiltration process, which enables uniform distribution of added materials with cost-effective way. We investigated the performance of PEMFC membrane-electrode assembly (MEA) with cerium oxide treated cathode. PEMFC performance was evaluated by current-voltage measurement and cyclic voltammetry. Also, the long term stability of cerium oxide treated PEMFC MEA has been analyzed with electrocatalyst accelerated degradation protocol proposed by Department of Energy (DOE). In brief, performance and long term stability enhancement of PEMFC MEA has been observed in cerium oxide treated samples. In our presentation, detail process of experiment and PEMFC performance analysis will be introduced.

Oxide electrodes are known to significantly improve reliability problems, such as fatigue and retention, in Pb(Zr, Ti)O3(PZT)-based ferroelectric capacitors. To understand the roles of the oxide electrodes on the opposite-state retention, we investigated the isotope tracer experiments and hysteresis measurements on Ir/IrO2/PZT/Ir and Ir/PZT/Ir capacitors before and after the retention tests. The depth profile of isotopic 18O in the Ir/IrO2/PZT/Ir capacitor, measured by the second ion mass spectroscopy, shows little changes in the 18O and 16O distributions at the IrO2/PZT interface. In addition, the hysteresis measurements showed that the internal field created by the retention tests should be nearly the same for both capacitors, indicating that the IrO2 layer should not play an important role in compensating the interface defect charges (possibly, the oxygen vacancies).

Highly c-axis-oriented (Sr,Ba)Nb2O6 (SBN) films were grown on a seeded MgO(100) substrate via sol-gel method. The substrate was preseeded with epitaxial islands of SBN made by breaking up a continuous film into single-crystal islands by pores. Since the number of epitaxial nuclei was increased at the interface between the film and the substrate, the film on a seeded substrate had better highly orientation than that on unseeded substrate. The film having low Sr content exhibited better epitaxial growth because of the distorted unit-cell network and the change of lattice parameters of SBN thin film. For obtaining excellent optical properties, SBN:75 film was prepared on MgO substrate with SBN:25 composition seed layer. Because of low birefringence of refractive indices in the film having high Sr content, the optical scattering loss by the anisotropy of refractive indices was suppressed.

Germanium oxide glass thin films were prepared by the sol–gel method and annealed under reduced atmosphere to create more oxygen-deficient defects. The densification and crystallization were examined depending on sintering and annealing conditions. Thus, homogeneous germanium oxide thin films with a high content of oxygen vacancies were fabricated. Ultraviolet absorption and oxygen vacancies of the films were investigated as a function of annealing temperature and time. Optical absorption in the 5-eV region due to the formation of oxygen vacancies is enhanced with increasing annealing temperature and time. The formation energy of oxygen vacancies is calculated to be about 1.0 eV.

Strontium barium niobate thin films were prepared by sol-gel method on various substrates using an improved process, two-step heating process. The two-step heating process applies an additive heat-treatment before crystallization for enhancement of the densification and the nucleation of films. Also, highly c-axis oriented SBN thin films with various compositions were obtained on MgO(100) and Pt(100)/MgO(100) substrates. Their optical and electrical properties such as optical propagation loss, refractive index, P-E hysteresis, and dielectric constant, were characterized as a function of the film composition.

Germanium oxide and germanosilicate glass films were fabricated using a sol–gel spin coating method. The formation and photobleaching of the optical absorption band of the films in the 5-eV region were measured as a function of annealing under a reducing atmosphere and ultraviolet (UV) illumination. A greater amplitude in the 5-eV absorption band was observed with increasing annealing time due to the formation of more germanium-related oxygen vacancies in the films. Also, the photobleaching of the absorption band increased with increasing illumination time. Although the amplitude of the absorption band in 50GeO2–50SiO2 glass films is greater than that in germanium oxide glass films because of higher annealing temperature, germanium oxide glass films are more photosensitive due to the greater photobleachable neutral oxygen monovacancy (NOMV) concentration than non-photobleachable neutral oxygen divacancy (NODV) concentration in the films.

Highly oriented lead lanthanum titanate (PLT) thin films on MgO (100) and c-plane sapphire single-crystal substrates have been prepared using the sol-gel process. The orientation and the mechanism of the highly preferred oriented PLT films derived sol-gel process have been investigated. The sol-gel PLT films fabricated on MgO (100) and c-plane sapphire substrates grow preferentially with (100) and (111) crystallographic orientations respectively, regardless of the film thickness and La content. In addition, it is confirmed that the tetragonality of the PLT perovskite structure decreases with an increase of La content. The a-axis orientation of the sol-gel PLT film on MgO (100) substrate is controlled only by formation of the intrinsic tensile stress during the crystallization of the film.

Using sol-gel processing method, thin films of lathanum modified lead titanate (PLT) on Corning 7059 glass were prepared. Differential thermal analysis (DTA/TG) curve of gel powder and infrared spectra (FT-IR) of the films were measured to estimate proper heating schedule. Microstructures of the films were observed using a scanning electron microscope (SEM). The waveguiding properties and the propagation loss were measured using the prism coupling method. Effects of the drying conditions on the refractive indices and the propagation losses of the films were investigated. Experimental results showed that the grain size and the content of residual organics in the film decreased as the drying temperature of the film increased. As the drying temperature increased, the refractive index increased and the propagation loss decreased.

Lead lanthanum titanate [(Pb,La)TiO{sub 3}] sol-gel films have been prepared to investigate the effect of heat treatment on the fabrication of uniform and crack-free thick films by applying different heating schedules. The surface morphology as well as the optical properties such as refractive index, optical transmission, and optical propagation loss of the films was examined depending on the film thickness. Because the slower and longer heating is enough to remove the organic and nitrate residues and diminish the thermal shock during heating the films, the slower and longer heating can produce the uniform and crack-free thick films having higher refractive index as well as lower optical propagation loss. Also, the drying and heating the films on hot plate in every coating resulted in the fabrication of thick films having above 8000 {Angstrom} without any defects and microcracks. This film presented the highest refractive index as well as the lowest optical propagation loss which grows exponentially with increasing the film thickness due to the scattering of defects in the film. {copyright} {ital 1997 Materials Research Society.}

There have been lots of effort to lower the operating temperature of solid oxide fuel cell (SOFC) below intermediate temperature (IT) regime (< 500 °C) because the high operating temperature (> 800 °C) of SOFCs causes various problems such as thermal stress, mechanical degradation and long startup time. At sub-IT, sluggish oxygen reduction reaction (ORR) at the cathode surface is considered as the rate determining step and it limits the practical use of SOFC at sub-IT region. Although Pt is known as the best catalyst for ORR, it is uneconomical due to its high price. Ag is considered as a great alternative for Pt cathode because of its high ORR activity and its relatively lower price compared to Pt. However, Ag agglomerates easily even at the low temperature region due to its low thermal stability. This agglomeration causes radical decrease of triple phase boundary (TPB) region where ORR occurs. In this study, we introduce atomic layer deposited yttria-stabilized zirconia (ALD YSZ) nano-particulate on Ag cathode in order to expand the TPB region of the cathode. ALD YSZ nano-particulate was deposited on the surface of porous Ag cathode made by DC sputtering. Fuel cell performance of Ag-ALD YSZ cathode was evaluate at the region of 250–450 °C. We will discuss the enhanced performance of ALD YSZ-treated Ag cathode in terms of morphology, electrochemical impedance and fuel cell performance.

Photobleaching of the optical absorption band in the 5-eV region of sol-gel-derived germanium oxide glass thin films was examined with the irradiation of the 5-eV light. The photobleaching represented by the saturated absorption coefficient change (−Δα) and the ratio of the neutral oxygen monovacancies to neutral oxygen divacancies concentrations for the germanium oxide were 175 cm−1 and 0.113, respectively. These values are larger than those of the pure germanium oxide bulk glass as well as germanosilicate thin films. The changes in bonding configuration around Ge atom by ultraviolet illumination were analyzed using x-ray photoelectron spectroscopy.

Highly c-axis oriented SBN films with various compositions were obtained on MgO(100) substrates using sol-gel process. Although the sol-gel process has been developed for ferroelectric thin films, it is known as being hard to fabricate highly oriented films. Thus, the preferential orientation of the films was enhanced by two methods: (1) poling the film by a high dc electric field (greater than Ec) and (2) growing the film on an SBN-seeded MgO substrate. The mechanisms of these methods were discussed. For their optical applications, second-harmonic generation (SHG) effect of SBN films was studied. Fundamental beam of Nd:YAG laser with 1064 nm was used as a pump beam. From Maker fringe measurements with a quartz reference, second- order nonlinear optical (NLO) coefficients d of the films were obtained. The second-order NLO coefficients of the films could be enhanced to considerable extent by applying the electric poling and using a self-seeds layer. These phenomena indicate that the SHG effect is sensitive to crystallographic structure as well as ferroelectric polarization. Mathematical equation was derived to correlate this microstructure to the SHG effect of SBN films.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper focuses on increasing the mechanical strength of hydrogels that connect silica particles via acrylic acid polymer chains. This is done by directly polymerizing the silica particle surfac...

Highly c-axis oriented SBN thin films with various compositions were obtained on MgO(100) and Pt(100)/MgO(100) substrates. The anisotropy of refractive indices (no and nc) of c-axis preferred oriented films on MgO(100) substrates decreases certainly as Sr content in the film composition increases. The optical propagation loss of the films decreases with increasing Sr content due to the reduction of the optical scattering by the anisotropy of refractive indices. The oriented films show the linear electro-optic effect with large electro-optic coefficients. The coefficient of the films increases as the Sr content increases because the linear electro-optic coefficient is dependent on the spontaneous polarization and the dielectric constant of the films.

The preparation and the optical characteristics of highly oriented PLT thin films are investigated. PLT films fabricated on MgO(100) and c-plane sapphire substrates have highly grown in (100) and (111) orientations, respectively. PLT films with high La content have a near cubic structure and weak anisotropy of refractive indices. The optical propagation losses of PLT films decrease as the La content of the films increases due to a complex interaction of surface roughness reduction and a reduction in the anisotropy refractive index. However, optical scattering in thicker sol-gel PLT thin film waveguides occurs by the internal scattering mechanism from the defects and the interfaces rather than by the surface scattering mechanism.

A two-beam polarization interferometer in a reflection configuration is used to measure the electro-optic coefficients of highly oriented strontium barium niobate thin films prepared by a sol-gel method. The technique enables the determination of the electro-optic coefficients of films using a strong Fabry–Perot effect with automatic adjustment and maintenance of the operation point of the interferometer. The linear electro-optic coefficients increase with increasing Sr content in the films.