• Tribology and Lubricants
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• v.30 no.1
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• pp.59-63
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• 2014

Laser Surface Texturing(LST) is a surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact surface. In LST technology, a pulsated laser beam is used to create arranged dimples on a surface by a material ablation process, which can improve such as load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on the bearing steel(AISI 52100) to create arranged dimples. To optimize the surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by combining circles, ellipses and the laser ablation process. The tribological testing of multi-scale textured surface was performed by a flat-on-flat unidirectional tribometer under lubrication and the results compared with that of the non-textured surface. Through an increase in sliding speed, the beneficial effect of multi-scale LST performance was achieved. The multi-scale textured surface had lower friction coefficient performances than the non-textured surface due to the hydrodynamic lubrication effect.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.749-753
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• 2010

We investigated the haze and the surface roughness of textured Si substrates etched by $XeF_2$ etching system with the etching parameters of $XeF_2$ pressure, etching time, and etching cycle. Here the haze was obtained as a function of wavelength from the measured reflectance. The haze of textured Si substrates was strongly affected by the etching parameter of etching cycle. The surface roughness of textured Si substrates was calculated with the haze and the scalar scattering theory at the wavelength of 800 nm. Then, the surface roughness was compared with that measured by atomic force microscope. The surce roughness obtained by two methods was changed with the similar tendency n terms of $XeF_2$ etching conditions.

• Textile Coloration and Finishing
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• v.25 no.1
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• pp.47-55
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• 2013

Physical properties of the composite yarn using low-melting(LM) polyester/Tencel were investigated with air-jet texturing conditions such as temperature, take-up overfeed, yarn speed and air pressure. Surface morphology, microstructure, tensile property, glossiness were evaluated. Surface morphology of a composite yarn had more damaged and loosened structure according to increase of take-up overfeed, yarn speed and air pressure. Crystallinity was affected by parameters such as temperature, yarn speed, take-up overfeed and air pressure and especially, yarn speed was most effective for increase of crystallinity. Also, it was found that temperature and air pressure had significantly affected tensile properties of a composite yarn. The glossiness of yarn increased with increase of temperature, yarn speed and air pressure.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.245-248
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• 2011

Many researches have been carried out to improve light absorption in the crystalline silicon solar cell fabrication. The rear reflection is applied to increase the path length of light, resulting in the light absorption enhancement and thus the efficiency improvement mainly due to increase in short circuit current. In this paper, we manufactured the silicon solar cell using the mono crystalline silicon wafers with $156{\times}156mm^2$, 0.5~3.0 ${\Omega}{\cdot}cm$ of resistivity and p-type. After saw damage removal, the dielectric film ($SiN_x$)on the back surface was deposited, followed by surface texturing in the KOH solution. It resulted in single-side texturing wafer. Then the dielectric film was removed in the HF solution. The silicon wafers were doped with phosphorus by $POCl_3$ with the sheet resistance 50 ${\Omega}/{\Box}$ and then the silicon nitride was deposited on the front surface by the PECVD with 80nm thickness. The electrodes were formed by screen-printing with Ag and Al paste for front and back surface, respectively. The reflectance and transmittance for the single-sided and double-sided textured wafers were compared. The double-sided textured wafer showed higher reflectance and lower transmittance at the long wavelength region, compared to single-sided. The completed crystalline silicon solar cells with different back surface texture showed the conversion efficiency of 17.4% for the single sided and 17.3% for the double sided. The efficiency improvement with single-sided textured solar cell resulted from reflectance increase on back surface and light absorption enhancement.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.433-438
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• 2013

In this paper, we found surface shapes are affected by several parameters of RIE, such as RF power, pressure, temp, and process times. The reflectance of pyramid and half sphere structures show differences among shapes, size, height, and depth of those structures. We made about $1{\mu}m$ pyramid and half sphere shapes of silicon surface with RIE. For comparing the reflectance, pyramid and half sphere structures are fabricated with same height. Pyramid structure cell shows higher cell efficiency of 12.5% by 1.1% than one of half sphere structure of 11.4%. The light absorption is more increased through the pyramid structure than half sphere structure.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.383-387
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• 2009

Multi-crystalline silicon surface etching without grain-boundary delineation is a challenging task for the fabrication of high efficiency solar cell. The use of sodium hydroxide - sodium hypochlorite (NaOH40% + NaOCl 12%) solution for texturing multi-crystalline silicon wafer surface in solar cell fabrication line is reported in this article. in light current-voltage results, the cells etched in NaOH 40% + NaOCl 12% = 1:2 exhibited higher short circuit current and open circuit voltage than those of the cells etched in NaOH 40% + NaOCl 12% = 1:1 solution. we have obtained 15.19% conversion efficiency in large area(156cm2) multi-Si solar cells etched in NaOH 40% + NaOCl 12% = 1:1 solution.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.86-86
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• 2010

Micro- and nanoscale texturing and control of surface energy have been considered for superhydrophobicity on polymer and silicon. However these surfaces have been reported to be difficult to meet the robustness and transparency requirements for further applications, from self cleaning windows to biochip technology. Here we provided a novel method to fabricate a nearly superhydrophobic soda-lime glass using two-step method. The first step involved wet etching process to fabricate micro-sale patterns on soda-lime glass. The second step involved application of $SiO_x$-incorporated DLC to generate high intrinsic contact angle on the surface using chemical vapor deposition (CVD) process. To investigate the effect of surface roughness, we used both positive and negative micro-scale patterns on soda-limeglass, which is relatively hard for surface texturing in comparison to quartz or Pyrex glasses due to the presence of impurities, but cheaper. For all samples we tested the static wetting angle and transparency before and after 100 cycles of wear test using woolen steel. The surface morphology is observed using optical and scanning electron microscope (SEM). The results shows that negative patterns had a greater wear resistance while the hydrophobicity was best achieved using positive patterns having static contact angle up to 140 deg. with about 80% transparency. The overall experiment shows that positive patterns at etching time of 1 min shows the optimum transparency and hydrophobicity. The optimization of micro-scale pattern to achieve a robust, transparent, superhydrophobic soda-lime glass will be further investigated in the future works.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.61-65
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• 2009

We produced noble surface structure of crystalline Si for solar cells by using preferential aqueous etching on crystallographic defects which were induced by grinding process. We analyzed the reflectance of textured surface according to surface topography resulting from various etchant concentrations and duration of etching process. The crystallographic defects and textured surface topography were investigated by using transmission electron microscopy and secondary electron microscopy, respectively. Also, the measurement of reflectance of textured surface utilizes spectrophotometer. The optimized texture surface exhibits improved result indicating reflectance of below ave. 1%. And it is cost-effective as well as taking short time within a few minutes.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.92-92
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• 2009

실리콘 기판과 비정질 실리콘 박막 사이의 계면특성은 실리콘 이종접합 태양전지의 효율을 높이는데 있어서 중요한 요소이다. 이종접합 태양전지에서는 n형 실리콘 기판 위에 비정질 실리콘 막을 증착시키는데 이 때 비정질 실리콘 막이 증착되면서 (111)면과 (111)면이 만나는 조직화된 피라미드의 골 사이에서 부분적으로 실리콘의 에피층이 성장하게 된다. 이 에피층이 결정질 실리콘 기판과 비정질 실리콘 막 사이의 계면 특성을 떨어뜨려 이종접합 태양전지의 효율이 감소하게 된다. 본 연구에서는 n형 실리콘 기판을 이용한 고효율 실리콘 이종접합 태양전지 제작을 위하여 실리콘 기판의 조직화 상태를 다르게 하여 셀을 제작하였다. 이에 큰 피라미드 형상의 조직화된 기판 표면, 작은 피라미드 형상의 조직화된 기판 표면, 큰 피라미드 형상을 라운딩 시킨 기판 표면, 작은 피라미드 형상을 라운딩 시킨 기판 표면을 제작하여 기판 종류에 따른 이종접합 태양전지를 제작하여 특성을 비교 하였다.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.393-397
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• 2003

To investigate the effect of AIN c-axis orientation on the resonance performance of film bulk acoustic wave resonators, solidly mounted resonators with crybtallographically different AIN piezoelectric films were prepared by changing only the bottom electrode surface conditions. As increasing the degree of c-axis texturing, the effective electromechanical coupling coefficient ($\kappa$$\_$eff/)$^2$ in resonators increased gradually. The least 4 degree of full width at half maximum in an AIN(002) rocking curve, which corresponds to $\kappa$$^2$$\_$eff/ of above 5%, was measured to be necessary for band pass filter applications in wireless communication system. The longitudinal acoustic wave velocity of AIN films varied with the degree of c-axis texturing. The velocity of highly c-axis textured AIN film was extracted to be about 10200 n/s by mathematical analysis using Matlab.