• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.249-249
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• 2010

We investigated novel surface treatment and its impact on silicon photovoltaic cells. Using 2-step etching methods, we have changed the nanostructure on pyramid surface so that less light is reflected. This work proposes an improved texturing technique of mono crystalline silicon surface for solar cells with sub-nanotexturing process. The nanotextured silicon surface exhibits a lower average reflectivity (~4%) in the wavelength range of 300-1100nm without antireflection coating layer. It is worth mentioning that the surface of pyramids may also affect the surface reflectance and carrier lifetime. In one word, we believe nanotextruing is a promising guide for texturization of monocrystalline silicon surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.1027-1031
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• 2001

A new constant growth technique to conserve an initial grating height of V-groove AlGaAs/InGaAs quantum nanostructures above 1.0 $\mu\textrm{m}$ thickness has been successfully embodied on submicron gratings using low pressure metalorganic chemical vapor deposition. A GaAs buffer prior to an AlGaAs barrier layer on submicron gratings plays an important role in overcoming mass transport effects and improving the uniformity of gratings. Transmission electron microscopy (TEM) image shows that high-density V-groove InGaAs quantum wires (QWRs) are well confined at the bottom of gratings. The photoluminescence (PL) peak of the InGaAs QWRs is observed in the temperature range from 10 to 280 K with a relatively narrow full width at half maximum less than 40 meV at room temperature PL. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystal.

• Journal of the Korean Ceramic Society
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• v.55 no.1
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• pp.1-20
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• 2018

Semiconducting nanomaterials have attracted considerable interest in recent years due to their high sensitivity, selectivity, and fast response time. In addition, for portable applications, they have low power consumption, lightweight, simple in operation, a low maintenance cost. Furthermore, it is easy to manufacture microelectronic sensor structures with metallic oxide sensitive thin layers. The use of semiconducting metal oxides to develop highly sensitive chemiresistive sensing systems remains an important scientific challenge in the field of gas sensing. According to the sensing mechanisms of gas sensors, the overall sensor conductance is determined by surface reactions and the charge transfer processes between the adsorbed species and the sensing material. The primary goal of the present study is to explore the possibility of using semiconducting mixed metal oxide nanostructure as a potential sensor material for selective gases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.723-730
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• 2003

The CN(carbon nitrogen) nanofibers were formed by HIP(high isostatic pressure) process. From the field emission measurement, CN nanofibers shows an excellent characteristics of emitter, better than CNTs and carbon nanofibers. The structures obtained can be divided into three groups : bamboo-like fibers, corrugated structures and bead necklace-like fib res. Emission properties of CN nanofibers were investigated for spacing, between anode and cathode, variation. Turn-on fields was 1.4 v/$\mu\textrm{m}$. The time reliability and light emission test were carried out for about 100 hours. We suggest that CN nanofibers can be possibly applied to the high brightness flat lamp because of low turn-on field and time reliability

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.130-131
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• 2006

In the present research work was searched the influence of severe plastic deformation (SPD) realized by ECAP (equalchannel angular pressing) on structural, mechanical and plastic properties of IF (interstitial free) steel. For physical simulation ECAP process with right angle channels $(90^{\circ})$ was used. The ECAP process was numerical simulated (namely its course of temperature, strain and stress fields and deformation forces) by FormFEM software, too.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.11
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• pp.873-877
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• 2012

The effect of oxygen pressure in the synthesis of ZnO nanostructures through thermal evaporation of Zn powder was investigated. The thermal evaporation process was carried out in oxygen ambient for 1 hr at $1,000^{\circ}C$ under different pressures. The oxygen pressure was changed in range of 0.5 ~ 900 Torr. Any nanostructure was not formed on the specimens prepared at oxygen pressures lower than 10 Torr. When oxygen pressure was 100 Torr, ZnO nanowires were observed. With increasing the oxygen pressure to 500 Torr, the morphology of ZnO nanostructures changed from wire to tetrapod. For all the samples, room temperature photoluminescence spectra show a strong green emission peak at around 550 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.63-64
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• 2007

Polystyrene-block-polymethyl methacrylate (PS-b-PMMA) can pattern nanoscale structures over large areas. However these patterns have a short-range order. These short-range order limits their utility in some applications. Consequently, we have to overcome this limitation of block-copolymer. In this study we added a electrical field to the standard block-copolymer patterning method for long-range ordered arrays of nanostructures. This method is conformed by annealing a block copolymer with applied voltages. It is very simple method that do not have any additional hour. In this reason it can be applied easily for other nanostructure fabrications. This method opens up a new route to the controlled phase separation of block copolymers with precise place of the nanostructures.

• Prospectives of Industrial Chemistry
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• v.23 no.3
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• pp.32-41
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• 2020

사람들은 대부분의 시간을 실내에서 보내고 있으며, 실내에 존재하는 유해가스는 미량의 농도에도 불구하고 심각한 질환을 일으킬 수 있다. 금속산화물 반도체 가스센서는 감도가 우수하고, 구조가 간단하며, 초소형화가 가능한 장점이 있어 고가의 대형 장비를 사용하지 않고 실내 유해가스를 측정하는 데 효과적으로 이용될 수 있다. 본 기고문에서는 금속산화물 반도체를 이용한 가스 센서의 검지 원리를 고찰하고, 나노 구조 조절, 마이크로 리액터 및 이중층 구조를 이용한 가스 개질 등 실내 유해가스 측정을 위한 다양한 센서 설계방법을 소개하고자 한다.

• Advances in nano research
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• v.1 no.2
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• pp.71-82
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• 2013

A simple chemical precipitation technique is reported for the synthesis of a hybrid nanostructure of single-wall carbon nanotubes (SWCNT) and titania ($TiO_2$) nanocrystals of average size 5 nm, which may be useful as a prominent photocatalytic material with improved functionality. The synthesized hybrid structure has been characterized by transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDAX), powder X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It is clearly revealed that nearly monodispersed titania nanocrystals (anatase phase) of average size 5 nm decorate the surfaces of SWCNT bundles. The UV-vis absorption study shows a blue shift of 16 nm in the absorbance peak position of the composite material compared to the unmodified SWCNTs. The photoluminescence study shows a violet-blue emission in the range of 325-500 nm with a peak emission at 400 nm. The low temperature electrical transport property of the synthesized nanomaterial has been studied between 77-300 K. The DC conductivity shows semiconductor-like characteristics with conductivity increasing sharply with temperature in the range of 175-300 K. Such nanocomposites may find wide applications as improved photocatalyst due to transfer of photo-ejected electrons from $TiO_2$ to SWCNT, thus reducing recombination, with the SWCNT scaffold providing a firm and better positioning of the catalytic material.

• Structural Engineering and Mechanics
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• v.73 no.3
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• pp.225-238
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• 2020

This work treats the axisymmetric buckling of functionally graded (FG) porous annular/circular nanoplates based on modified couple stress theory (MCST). The nanoplate is located at the elastic medium which is simulated by Kerr foundation with two spring and one shear layer. The material properties of the porous FG nanostructure are assumed to vary through the nanoplate thickness based on power-law rule. Based on two variables refined plate theory, the governing equations are derived by utilizing Hamilton's principle. Applying generalized differential quadrature method (GDQM), the buckling load of the annular/circular nanoplates is obtained for different boundary conditions. The influences of different involved parameters such as boundary conditions, Kerr medium, material length scale parameter, geometrical parameters of the nanoplate, FG power index and porosity are demonstrated on the nonlinear buckling load of the annular/circular nanoplates. The results indicate that with increasing the porosity of the nanoplate, the nonlinear buckling load is decreased. In addition, with increasing the material length scale parameter to thickness ratio, the effect of spring constant of Kerr foundation on the buckling load becomes more prominent. The present results are compared with those available in the literature to validate the accuracy and reliability. A good agreement is observed between the two sets of the results.