• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.150-156
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• 1996

RWG MQW-LD has been made with our vertical LPE system from the optimal design condition for the RWG MQW-LD to be activated as weakly index-guided LD. Through several experiments we have established the growth condition which can be used through to grow the MQW-DH wafer and to control the thickness of MQW layer to ~200$\AA$. 4 ${\mu}{\textrm}{m}$-thickness of the ridge pattern has been formed through the photolithographic process on the MQW-DH wafer grown by the former condition, and then we have fabricated the RWG MQW-LD using it. From the result of measuring the electro-optical characteristics we can make sure that it can be lasing as lasing as laterally single mode at even more than $2.7I_{th}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1181-1185
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• 2005

Microstereolithography has evolved from the stereolithography technique, and is also based on a light-induced layer-stacking manufacturing. Integral microstereolithography is proposed for building a 3D microstructure rapidly, which allows the manufacture of a complete layer by one irradiation only. In this study, we developed the integral microstereolithography apparatus based on the use of $DMD^{TM}$ as dynamic pattern generator. It is composed of Xenon-Mercury lamp, optical devices, pattern generator, precision stage, controllers and the control program. Also, we estimated curing characteristics in photopolymer. The relationship between the viscosity of diluent-oligomer solutions and curing width, irradiation time and curing property has been studied.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.743-746
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• 2003

We have successfully used hydrophobic direct-wafer bonding, along with H-induced layer splitting of Ge, to transfer 700nm think, single-crystal Ge films to Si substrates. Optical and electrical properties have been also observed on these samples. Triple-junction solar cell structures gown on these Ge/Si heterostructure templates show comparable photoluminescence intensity and minority carrier lifetime to a control structure grown on bulk Ge. When heavily doped p$^{+}$Ge/p$^{+}$Si wafer bonded heterostructures were bonded, ohmic interfacial properties with less than 0.3Ω$\textrm{cm}^2$ specific resistance were observed indicating low loss thermal emission and tunneling processes over and through the potential barrier. Current-voltage (I-V) characteristics in p$^{+}$Ge/pSi structures show rectifying properties for room temperature bonded structures. After annealing at 40$0^{\circ}C$, the potential barrier was reduced and the barrier height no longer blocks current flow under bias. From these observations, interfacial atomic bonding structures of hydrophobically wafer bonded Ge/Si heterostructures are suggested.ested.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.378-378
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• 2007

In this study, liquid crystal (LC) aligning capabilities for homeotropic alignment on the $ZrO_x$ thin film by electron beam evaporation method were investigated. Also, the control of pretilt angles and thermal stabilities of the NLC treated on $ZrO_x$ thin film were investigated. The uniform LC alignment on the $ZrO_x$ thin film surfaces and good thermal stabilities with electron beam evaporation can be achieved. It is considerated that the LC alignment on the $ZrO_x$ thin film by electron beam evaporation is attributed to elastic interaction between LC molecules and micro-grooves at the $ZrO_x$ thin film surface created by evaporation. In addition, it can be achieved the good electro-optical (EO) properties of the VA-LCD on $ZrO_x$ thin film layer with. oblique electron beam evaporation.

• Journal of the Korean Vacuum Society
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• v.21 no.4
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• pp.205-211
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• 2012

We investigated the optical and hydrophobic properties of the deposited silver (Ag) zinc oxide (ZnO) nanorods (NRs) on flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates (i.e., ITO/PET). The ZnO NRs were grown by an electrochemical deposition using a sputtered ZnO seed layer and the Ag was deposited by using a thermal evaporator. For comparison, the same fabrication process was carried out on the bare ITO/PET without ZnO NRAs. Due to the discrete surface of ZnO NRs, the deposited Ag was formed as nano-scale particles, while the Ag became film-like for bare ITO/PET. In order to control the size and amount of Ag particles, the Ag deposition time was changed from 100 to 600 s. When the deposition time was increased, the Ag particles became larger and denser, and the absorptance was increased. This enhanced absorptance may be due to the localized surface plasmon resonance of Ag particles. Furthermore, the relatively high hydrophobicity was observed for the deposited Ag on the ZnO NRs/ITO/PET. These improved optical and surface properties are expected to be useful for flexible photovoltaic and optoelectronic devices.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2461-2466
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• 2003

This paper presents a simple sensor fusion algorithm using neural network for navigation of mobile robots with obstacle avoidance and trap recovery. The multiple sensors input sensor data to the input layer of neural network activating the input nodes. The multiple sensors used include optical encoders, ultrasonic sensors, infrared sensors, a magnetic compass sensor, and GPS sensors. The proposed sensor fusion algorithm is combined with the VFH(Vector Field Histogram) algorithm for obstacle avoidance and AGPM(Adaptive Goal Perturbation Method) which sets adaptive virtual goals to escape trap situations. The experiment results show that the proposed low-level fusion algorithm is effective for real-time navigation of mobile robot.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.249.1-249.1
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• 2015

Quantum dots (QDs) are attracting growing attention for photovoltaic device applications because of their unique electronic, optical and physical properties. Lead sulfide (PbS) QDs are one of the most widely studied materials for the devices and known to have size-tunable properties. In this context, we investigated the relationship between the size of PbS QDs and two synthesizing conditions, a concentration of ligand, oleic acid in this work, and injection temperature. The inverted colloidal quantum dot solar cells based on the heterojunction of n-type zinc oxide layer and p-type PbS QDs were also fabricated. The size of the QDs and cell properties were observed to depend on both the QD synthesizing conditions, and hence the overall efficiency of the cell could vary even though the size of QDs used was same. The QD synthesizing conditions were finally optimized for the maximum cell efficiency.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.100-100
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• 2003

An image processing algorithm has been developed in order to analyze the nanofiber web images obtained from a high magnification microscope. It has been known that precise pore detection on thick webs is extremely difficult mainly due to lack of light uniformity, difficulty of fine focusing and translucency of nanofiber web. The pore detection algorithm developed has been found to show excellent performance in characterizing the porous structure, thus being a promising tool for on-line quality control system under mass production. Since the images obtained from an optical microscope represent only web surface, a scale factor has been introduced to estimate the web structure as a whole. Resulting web structures have been compared to those by mercury porosimetry, especially in pore size distribution. It has been shown that those two structures have a strong correlation, indicating that scaling of a single layer web structure can be an effective way of estimating the structure of thick fiber webs.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.34-38
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• 2005

This is a widespread requirement for low cost lightweight thermal imaging sensors for both military and civilian applications. Today, a large number of uncooled infrared detector developments are under progress due to the availability of silicon technology that enables realization of low cost IR sensor. System prices are continuing to drop, and swelling production volume will soon drive process substantially lower. The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple Structurefor developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. This paper reports a micromachined silicon uncooled thermal imager intended for applications in automated process control. This paper presents the design, fabrication, and the behavior of cantilever for thermomechanical sensing.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1219-1221
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• 1997

Poly(1,4-phenylene(1-methoxyenthylene)), organic water soluble PPV precursor was synthesized for polymer electroluminescence(EL) device. To control the molecular array, deposition method of emitter was Langmuir-Blodgett(LB). PPV precursor layer was treated thermally to conversion of PPV. Optical, electrical and EL properties of PPV LB thin film was estimated. Homogeneous light emission of greenish-yellow in PPV LB thin film can be easily confirmed under normal lighting even at low driving voltage. Polymer EL device using PPV LB thin film as emitter materials had a possibility to apply to next generation display device.