• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.72-72
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• 2011

Surface science is intrinsically related to the performance of solar cells. In solar cells the generation and collection of charge carriers determines their efficiency. Effective transport of charge carriers across interfaces and minimization of their recombination at surfaces and interfaces is of utmost importance. Thus, the chemistry at the surfaces and interfaces of these devices must be determined, and related to their performance. In this talk we will discuss the role of two important interfaces, First, the role of surface passivation is very important in limiting the rate of carrier of recombination. Here we will combine x-ray photoelectron spectroscopy of the surface of a Si device with electrical measurements to ascertain what factors determine the quality of a solar cell passivation. In addition, the quality of the heterojunction interface in a ZnSe/CdTe solar cell affects the output voltage of this device. X-ray photoelectron spectroscopy gives some insight into the composition of the interface, while ultraviolet photoemission yields the relative energy of the two materials' valence bands at the junction, which controls the open circuit voltage of the solar cell. The relative energies of ZnSe and CdTe at the interface is directly affected by the material quality of the interface through processing.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.4-4
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• 2012

Proteins enable biology to be viable through molecular interactions (such as in antigen-antibody, ligand-receptor, and drug-target) with

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.12
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• pp.1859-1864
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• 1990

The effect of H+ and OH- ion concentrations at doped Si semiconductor/pH buffer solution interfaces were investigated in terms of cyclic current-voltage characteristics. The effects of space charge on oppositely doped Si semiconductors, i.e., p-and n-Si semiconductors, can be effectively applied to study the pH effects and the slow surface states at the interfaces. The adsorptions of H+ and OH- inons on the doped Si semiconductor surfaces are physical adsorption rather than chemical adsorption. Adsorptive processes and charging effects of the slow surface states can be explained as the potential barrier variations and the related current-voltage characteristics at the interfaces. Under forward bias, the charged slow surface states on the p-and n-si semiconductor surface are donor and acceptor slow surface states, respectively. The effects of minority carriers on the slow surface states can be neglected at the doped Si semiconductor interfaces.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.221-226
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• 2002

One of the serious challenges in developing rotary compressor with HFC refrigerant is the prediction of scuffing times and wear amounts between vane and roller surfaces. In this study, the tribological characteristics of sliding surfaces using vane-roller geometry of rotary compressor were investigated. The sliding tests were carried out under various sliding speeds, normal loads and surface roughness. During the test friction force, wear depth, time to failure and surface temperature were monitored. Because severe wear was occurred on vane surface, TiN coating was applied on sliding surfaces to prolong the wear-life of vane-roller interfaces. From the sliding test it was found that there was the optimum initial surface roughness to break in and to prolong the wear life of sliding surfaces. Depending on the load and speed, the protective layers, which were composed of metallic oxide and organic compound, were formed on sliding surfaces. Those would play an important role in role amounts of friction and wear between miler and vane surfaces.

• Tribology and Lubricants
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• v.20 no.6
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• pp.337-342
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• 2004

One of the serious challenges in developing rotary compressor with HFC refrigerant is the prediction of scuffing times and wear amounts between vane and roller surfaces. In this study, the tribological characteristics of sliding surfaces using vane-roller geometry of rotary compressor were investigated. The sliding tests were carried out under various sliding speeds, normal loads and surface roughness. During the test, friction force, wear depth, time to failure and surface temperature were monitored. Because severe wear occurred on vane surface, TiN coating was applied on sliding surfaces to prolong the wear life of vane-roller interfaces. From the sliding test it was found that there was the optimum initial surface roughness to break in and to prolong the wear life of sliding surfaces. Depending on the load and speed, the protective layers, which were composed of metallic oxide and organic compound, were formed on sliding surfaces. Those would play an important role in the amounts of friction and wear between roller and vane surfaces.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.299-299
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• 2011

A dipolar interlayer can cause dramatic changes in the device characteristics of organic field-effect transistors (OFETs) or photovoltaics. A shift in the threshold voltage, for example, has been observed in an OFET where the organic semiconductor active layer is deposited on SiO2 modified with a dipolar monolayer. Dipolar molecules can similarly be used to change the current-voltage characteristics of organic-inorganic heterojunctions. We have conducted a series of experiments in which different molecular linkages are placed between a pentacene thin film and a silicon substrate. Interface modifications with different linkages allow us to predict and examine the nature of tunneling through pentacene on modified Si surfaces with different dipole moment. The molecular-scale structure and the tunneling properties of pentacene thin films on modified Si (001) with nitrobenzene and styrene were examined using scanning tunneling spectroscopy. Electronic interfaces using organic surface dipoles can be used to control the band lineups of a semiconductor at organic/inorganic interfaces. Our results can provide insights into the charge transport characteristics of organic thin films at electronic interfaces.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.227-228
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• 2002

One of the serious challenges in developing rotary compressor with HFC refrigerant is the prediction of scuffing times and wear amounts between vane and roller surface. In this study, the tribological characteristics of sliding surfaces using roller-vane geometry of rotary compressor were investigated. The sliding tests were carried out under various sliding speeds, normal loads and surface roughness. During the tests, friction force, wear scar width, time to failure, surface temperature, and surface roughness were monitored. Because severe wear was occurred on vane surface, TiN coating was applied on sliding surfaces to prolong the wear-life of vane-roller interfaces. From the sliding tests, it was found that there was the optimum initial surface roughness to break in and to prolong the wear life of sliding surfaces. Depending on load and speed, the protective layers, which were composed of metallic oxide and organic compound, were formed on sliding surfaces. Those would play an important role in the amount of friction and wear between roller and vane surfaces.

• ETRI Journal
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• v.25 no.6
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• pp.517-522
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• 2003

This investigation confirms that silver stearate consists of an infinite-sheet, two-dimensional, nonmolecular layered structure. Scanning electron microscopy, X-ray diffraction, and infrared spectroscopy reveal the following: plate-like morphology is identified from the SEM image, XRD peaks can be indexed to the (0k0) reflections of a layered structure, and infrared peaks show that alkyl chains are present in an all-trans conformational state with little or no significant gauche population. Based on these structural characteristics, we demonstrate that silver stearate, a prototype of layered organic-inorganic hybrid material, can be grown not only in a designed two-dimensional pattern but also in three-dimensionally ordered ways by using carboxyl-group terminated nanoparticles as a template.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.276-282
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• 2013

This paper proposes an ultrasonic method for measurement of linear and hysteretic interfacial stiffness of contacting surfaces between two steel plates subjected to nominal compression pressure. Interfacial stiffness was evaluated by the reflection and transmission coefficients obtained from three consecutive reflection waves from solid-solid surface using the shear wave. A nonlinear hysteretic spring model was proposed and used to define the quantitative interfacial stiffness of interface with the reflection and transmission coefficients. Acoustic model for 1-D wave propagation across interfaces is developed to formulate the reflection and transmission waves and to determine the linear and nonlinear hysteretic interfacial stiffness. Two identical plates are put together to form a contacting surface and pressed by bolt-fastening to measure interfacial stiffness at different states of contact pressure. It is found from experiment that the linear and hysteretic interfacial stiffness are successfully determined by the reflection and transmission coefficient at the contact surfaces through ultrasonic pulse-echo measurement.

• Computers and Concrete
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• v.29 no.4
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• pp.247-253
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• 2022

In this study, the problem of discontinuous contact in two functionally graded (FG) layers resting on a rigid plane and loaded by two rigid blocks is solved by the finite element method (FEM). Separate analyzes are made for the cases where the top surfaces of the problem layers are metal, the bottom surfaces are ceramic and the top surfaces are ceramic and the bottom surfaces are metal. For the problem, it is accepted that all surfaces are frictionless. A two-dimensional FEM analysis of the problem is made by using a special macro added to the ANSYS package program The solution of this study, which has no analytical solution in the literature, is given with FEM. Analyzes are made by loading different Q and P loads on the blocks. The normal stress (σy) distributions at the interfaces of FG layers and between the substrate and the rigid plane interface are obtained. In addition, the starting and ending points of the separations between these surfaces are determined. The normal stresses (σx, σy) and shear stresses (τxy) at the point of separation are obtained along the depth. The results obtained are shown in graphics and tables. With this method, effective results are obtained in a very short time. In addition, analytically complex and long problems can be solved with this method.