• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.213-217
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• 2005

The polymer light emitting diodes (PLED) with ITO/PEDOT:PSS/MEH-PPV/Al structure were prepared on ITO(indium tin oxide)/Glass substrates using PEDOT:PSS[poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] as the hole transport material and MEH-PPV[poly(2-methoxy-5-(2-ethyhexoxy)-1,4phenylenvinylene)] as emission material layer. The dependences on the surface roughnees and friction coefficient between film layers were investigated as a function of the MEH-PPV concentrations$(0.1\;wt\%\~0.9\;wt\%)$. The RMS values decreased from 1.72 nm to 1.00 nm as the concentration of MEH-PPV increased from $0.1\;wt\%\;to\;0.9\;wt\%$, indicating improvement of surface roughness. In addition, friction coefficients decreased from 0.048 to 0.035, which means the deteriorating of the adhesion condition. The PLED sample with $0.5\;wt\%$ of MEH-PPV showed the maximum luminance of $409\;cd/m^2$.

• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.123-129
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• 2003

Thin transparent Cu films in the thickness range of 10 ~ 40 nm are deposited by rf-magnetron sputtering on porous silicon (PS) anodized on p-type silicon in dark. Microstructural features of the Cu films are investigated using SEM, AFM and XRD techniques. The RMS roughness of the Cu films is found to be around 1.47 nm and the grain growth is columnar with a (111) preferred orientation and follows the Volmer-Weber mode. The photoluminescence studies showed that a broad luminiscence peak of PS near the blue-green region gets blue shifted (~0.05 eV) with a small reduction in intensity and therefore, Cu-related PL quenching is absent. The FTIR absorption spectra on the PS/Cu structure revealed no major change of the native PS peaks but only a reduction in the relative intensity. The I-V characteristic curves further establish the Schottky nature of the diode with an ideality factor of 2.77 and a barrier height of 0.678 eV. An electroluminiscence (EL) signal of small intensity could be detected for the above diode.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.353-358
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• 2008

In order to increase extraction efficiency of AlGaInP-based vertical RED LEDs, chemical wet etching technique was produced by using a roughened surface with triangle-like morphology. A commonly used $H_3PO_4$-based solution was applied for chemical wet etching. The light extraction of AlGaInP LED was related to the n-side roughed surface morphology. The morphology of roughed surface is analyzed by the atomic force microscope (AFM). As a result, the roughed surface AlGaInP LED has a root-mean-square (RMS) roughness of 44 nm. The brightness shows 41% increase after roughening n-side surface, as compared to the ordinary flat surface LED.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.151-156
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• 2015

In order to improve the properties of high-temperature superconducting wire for superconducting cable system, we optimized the electro-polishing (EP), ion-beam assisted deposition (IBAD), superconducting (SC) layer, and baking (heat) treatment. The buffer layer was deposited on electro-polished substrate with RMS roughness ($R_{RMS}$) less than 5 nm. The IBAD process was carried out at $V_{beam}$: 1100 V and $V_{accel}$: 850 V that resulted in highly crystalline film of $LaMnO_3$. Chemical composition of SC layer is key to higher critical current, and we found that composition can be determined by surface color of SC layer. We adopt a proprietary contorl system based on RGB analysis of the surface and achieved critical current of 150 A/4 mm-width. The proposed baking treatment resulted in decreasing of about 10% of fraction defects.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.1
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• pp.29-33
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• 2010

Titanium nitride (TiN) films were deposited on the polycarbonate substrate by using radio frequency (RF) magnetron sputtering without intentional substrate heating. After deposition, the films were bombarded with intense electron beam for 20 minutes. The intense electron irradiation impacts on the crystalline, hardness and surface roughness of the TiN films. The films irradiated with an electron beam of 300 eV show the small grains on the surface, while as deposited TiN films did not showany grains on the surface. Also the surface harness evaluated with micro indenter was increased up to 18 Gpa at electron energy of 900 eV after electron beam irradiation. In addition, surface root mean square (RMS) roughness of the films irradiated with intense electron beam affected strongly. The films irradiated by electron beam with 900 eV have the lowest roughness of 1.2 nm in this study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.9-15
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• 2019

This study focused on the application of ELID mirror-surface grinding technology to the manufacture of off-axis asymmetric large-area reflecting mirrors made of BK7 glass. The size of the parts, such as asymmetric large-area mirrors or lens, made form-accuracy or roughness especially hard to measure after machining because of the measuring range limit of measurement devices. In this study, the ELID grinding system has been set up for mirror-surface machining experiments manufacturing off-axis asymmetric lenses. A measuring method using a reference workpiece has been suggested to measure the form-accuracy and roughness. According to the experimental results, even when using only a reference workpiece, it is confirmed that the surface roughness was 8 nmRa and form-accuracy was 80 nmRMS, with a best fit asymmetric radius when using a grinding wheel of #8,000. It is found that the accuracy of large-area parts could be estimated by the proposed process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.99-105
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• 2014

$LiCoO_2$ thin film have received attention as cathodes of thin-film microbatteries. In this study, $LiCoO_2$ thin films were synthesized on Au substrates by sol-gel spin coating method and electrochemical properties were investigated under annealing temperature and time. The phycochemical properties of $LiCoO_2$ thin film were investigated by X-ray diffraction, scaning electron microscopy and atomic force microscopy. The electrochemical properties were characterized using galvanostatic charging/discharging cycling tests. From X-ray diffraction, as-grown films annealed at $550^{\circ}C$ and $750^{\circ}C$ are presumed to be spinel structure and a single phase of the layered-rock-salt, respectively. The RMS roughness and grain size of the films which annealed at $750^{\circ}C$ has similar values for annealing time 10 and 30 min, while for annealing time 120 min surface roughness, grain size increase and pore appearance were observed. The first discharge capacity of $LiCoO_2$ thin films annealed at $750^{\circ}C$ for 10, 30 and 120 min is about 54.5, 56.8 and $51.87{\mu}Ah/cm^2{\mu}m$, respectively. Corresponding capacity retention at 50th cycle is 97.25, 76.69, 77.19%.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.243-252
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• 2021

The present study aims to investigate the interaction of a wire-type turbulence stimulator and the laminar boundary layer on a flat plate by flow field measurement. For the towing tank tests, a one-dimensional Laser Doppler Velocimetry (LDV) attached on a two-axis traverse was used to measure the streamwise velocity component of the boundary layer flow in zero pressure gradient, disturbed by a turbulence stimulator. The wire diameter was 0.5 and 1.0 mm according to the recommended procedures and guidelines suggested by the International Towing Tank Conference. Turbulence development by the stimulator was identified by the skin friction coefficient, mean and Root Mean Square (RMS) of the streamwise velocity. The laminar boundary layer with the absence of the wire-type stimulator was similar to the Blasius solution and previous experimental results. By the stimulator, the mean and RMS of the streamwise velocity were increased near the wall, showing typical features of the fully developed turbulent boundary layer. The critical Reynolds number was reduced from 2.7×10⁵ to 1.0×10⁵ by the disturbances caused by the wire. As the wire diameter and the roughness Reynolds number (Rek) increased, the disturbances by the stimulator increased RMS of the streamwise velocity than turbulent boundary layer.

• Journal of Korea Water Resources Association
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• v.42 no.8
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• pp.619-629
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• 2009

The objective of this study is to estimate bed-resistance in gravel-bed rivers using the equivalent roughness height($k_s$). We calculated the friction factor(f) with the measured data from 8 domestic gravel-bed rivers and investigated the size distributions of the bed materials. The averaged $k_s$ in each cross-section, which is determined under the hypothesis that the vertical velocity distribution follows the logarithmic law, is compared with the reach $k_s$ which is calculated with the cumulative grain diameter distribution curve of bed materials. Moreover, the applicability of existing formulae, such as Strickler type equations, is examined by comparing with Manning's n value converted from the $k_s$. According to the results, the reach $k_s$ proves to be a good indicator of representative characteristic of bed materials in a reach, and the Manning's n based on the reach $k_s$ is appropriate for practical estimation of the bed-resistance, for RMS errors between calculated and measured Manning's n is less than 0.003. The correlation between the $k_s$ and specified bed-material size($D_i$) is very low, so it is difficult to select a proper one among the existing empirical equations.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.642-647
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• 2007

We investigated dry etching of acrylic (PMMA) in $O_2/N_2$ plasmas using a multi-layers electrode reactive ion etching (RIE) system. The multi-layers electrode RIE system had an electrode (or a chuck) consisted of 4 individual layers in a series. The diameter of the electrodes was 150 mm. The etch process parameters we studied were both applied RIE chuck power on the electrodes and % $O_2$ composition in the $N_2/O_2$ plasma mixtures. In details, the RIE chuck power was changed from 75 to 200 W.% $O_2$ in the plasmas was varied from 0 to 100% at the fixed total gas flow rates of 20 sccm. The etch results of acrylic in the multilayers electrode RIE system were characterized in terms of negatively induced dc bias on the electrode, etch rates and RMS surface roughness. Etch rate of acrylic was increased more than twice from about $0.2{\mu}m/min$ to over $0.4{\mu}m/min$ when RIE chuck power was changed from 75 to 200 W. 1 sigma uniformity of etch rate variation of acrylic on the 4 layers electrode was slightly increased from 2.3 to 3.2% when RIE chuck power was changed from 75 to 200 W at the fixed etch condition of 16 sccm $O_2/4\;sccm\;N_2$ gas flow and 100 mTorr chamber pressure. Surface morphology was also investigated using both a surface profilometry and scanning electron microscopy (SEM). The RMS roughness of etched acrylic surface was strongly affected by % $O_2$ composition in the $O_2/N_2$ plasmas. However, RIE chuck power changes hardly affected the roughness results in the range of 75-200 W. During etching experiment, Optical Emission Spectroscopy (OES) data was taken and we found both $N_2$ peak (354.27 nm) and $O_2$ peak (777.54 nm). The preliminarily overall results showed that the multi-layers electrode concept could be successfully utilized for high volume reactive ion etching of acrylic in the future.