• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.273-278
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• 2007

For the simulation of active region in the quantum cascade lasers (QCL), we solved Schrodinger equation utilizing Runge-Kutta method and Shotting method. Wavelength, phonon resonant energy, and dipole matrix element were simulated with the variation of active region thickness. As a result of such simulation, it was suggested the tolerance range of epi-layer thickness error when 3-quantum well QCL structures are grown.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.238-245
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• 2018

The skin experiences constant physical stimuli, such as stretching. Exposure to excessive physical stimuli stresses the skin and can accelerate aging. In this study, we applied a method that allowed human fibroblasts and keratinocytes to be perfused with media to form 3D skin equivalents that were then uniaxially 10%-stretched for 12 h per day (at either 0.01 or 0.05 Hz) for up to 7 days to form wrinkled skin-on-a-chip (WSOC). There was more wrinkling seen in skin equivalents under 0.01 Hz uniaxial stretching than there was for non-stretched skin equivalents. At 0.05 Hz, the stratum corneum almost disappeared from the skin equivalents, indicating that stretching was harmful for the epidermis. At both frequencies, the production of collagen and related proteins in the skin equivalents, such as fibronectin 10 and keratin, decreased more than those in the non-stretched equivalents, indicating that the dermis also suffered from the repeated tensile stress. These results suggest that WSOCs can be used to examine skin aging and as an in vitro tool to evaluate the efficacy of anti-wrinkle cosmetics and medicines.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.05a
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• pp.21.1-21.1
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• 2006

• Journal of Magnetics
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• v.17 no.4
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• pp.308-315
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• 2012

Experimental investigations of the magnetization, magnetostriction and magnetoelectric (ME) effects were performed on sandwich - type Metglas/PZT/Metglas laminate composites. The results have been analyzed by taking into account the demagnetization contribution. The study has pointed out that the magnetic flux concentration is strongly improved in piezomagnetic laminates with a narrower width leading to a significant enhancement of the ME effects. The piezomagnetic laminates with the optimal area dimension were integrated to form a 2-D geomagnetic device, which simultaneously can precisely detect the strength as well as inclination of the earth's magnetic field. In this case, a magnetic field resolution of better than $10^{-4}$ Oe and an angle precision of ${\pm}0.1^{\circ}$ were determined. This simple and low-cost geomagnetic-field device is promising for various applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.308-309
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• 2008

We have proposed a high performance liquid crystal display using two thin film transistors (TFTs) for the large size TFT-LCD desirably 42inch WXGA panel for TVs. The device generates stronger electric fields to reorient liquid crystals than that in the conventional IPS device because the voltages with opposite polarity with respect to the common electrode are applied to each finger-type electrode. As a result, the operation voltage of 2Tr-IPS mode can be decreased and the transmittance can be increased compared to conventional IPS device. Consequently, the 2Tr-IPS has all the advantages over conventional IPS from large size point of view.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.209-215
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• 2006

We investigated the optical property and the electronic subband structure of InAs quantum dots in an InAsGa/GaAs well structure utilizing photoluminescence (PL), PL excitation (PLE) and near infrared transmission spectroscopy. From transmission and PLE spectra, we found three bound states in the InAs quantum dot and two bound states in InGaAs/GaAs quantum well, and correlated to the results of intersubband transitions observed in photocurrent spectrum.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.266-271
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• 2009

We have investigated the lasing characteristics of GaAs-based 1300 nm wavelength region InAs Quantum Dot Laser Diode grown by Migration Enhanced Molecular Beam Epitaxy. Under a pulsed and CW operation, we observed the state switching of lasing wavelength from ground state (1302 nm) to excited state (1206 nm) due to the gain saturation of ground state. Under a pulsed operation, $J_{th}=92A/cm^2$, $\lambda_L=1311\;nm$ and under a CW operation, $J_{th}=247A/cm^2$, $\lambda_L=1320\;nm$.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.668-672
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• 2003

In order to reach the high electrical quality of organic thin film transistors (OTFTs) such as high mobility and on-off current ratio, it is strongly desirable to study the enhancement of electrical properties in OTFTs. Here, we report the novel method of hydrogen $(H_{2})$ plasma treatment to improve electrical properties in inverted staggered OTFTs based on pentacene as active layer. To certify the effect of this method, we compared the electrical properties of normal device as a reference with those of device using the novel method. In result, the normal device as a reference making no use of this method exhibited a field effect mobility of 0.055 $cm^{2}/Vs$, on/off current ratio of $10^{3}$, threshold voltage of -4.5 V, and subthreshold slope of 7.6 V/dec. While the device using the novel method exhibited a field effect mobility of 0.174 $cm^{2}/Vs$, on/off current ratio of $10^{6}$. threshold voltage of -0.5 V, and subthreshold slope of 1.49 V/dec. According to these results, we have found the electrical performances in inverted staggered pentacene TFT owing to this novel method are remarkably enhanced. So, this method plays a key role in highly improving the electric performance of OTFTs. Moreover, this method is the first time yet reported for any OTFTs

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.98-103
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• 2019

Optical filters to control light wavelength of displays or cameras are fabricated by multi-layer stacking process of low and high index thin films. The process of multi-layer stacking of thin films has received much attention as an optimal process for effective manufacturing in the optical filter industry. However, multi-layer processing has disadvantages of complicated thin film process, and difficulty of precise control of film morphology and material selection, all of which are critical for transmittance and coloring effect on filters. In this study, the composite $TiO_2$, which can be used to control of UV absorption, coated on nano hollow silica sol, was synthesized as a coating material for optical filters. Furthermore, systematic analysis of the process parameters during the chemical reaction, and of the structural properties of the coating solutions was performed using SEM, TEM, XRD and photo spectrometry. From the structural analysis, we found that the 85 nm nano hollow silica with 2.5 nm $TiO_2$ shell formation was successfully synthesized at proper pH control and titanium butoxide content. Photo luminescence characteristics, excited by UV irradiation, show that stable absorption of 350 nm-light, correlated with a 3.54 eV band gap, existed for the $TiO_2$ shell-nano hollow silica reacted with 8.8 mole titanium butoxide solution. Transmittance observed on substrate of the $TiO_2$ shell-nano hollow silica showed effective absorption of 200-300 nm UV light without deterioration of visible light transparency.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.340-343
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• 2008

This work reports the simple fabrication of the single cell gap transflective liquid crystal display (LCD) using wire grid polarizer. The nano sized wire grid polarizer was patterned on common electrode itself, on the reflective part of FFS (Fringe field switching) mode whereas the common electrode was unpatterned at transmissive part. However, this structure didn't show single gamma curve, so we further improved the device by patterning the common electrode at transmissive part. As a result, V-T curve of proposed structure shows single gamma curve. Such a device structure is free from in-cell retarder, compensation film and reflector and furthermore it is very thin and easy to fabricate.