• 한국전기전자재료학회논문지
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• 제29권6호
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• pp.370-375
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• 2016

In this paper, we investigated the electrical properties of crystalline silicon solar cell fabricated with Ni/Cu/Ag plating. The laser process was used to ablate silicon nitride layer as well as to form the selective emitter. Phosphoric acid layer was spin-coated to prevent damage caused by laser and formed selective emitter during laser process. As a result, the contact resistance was decreased by lower sheet resistance in electrode region. Low sheet resistance was obtained by increasing laser current, but efficiency and open circuit voltage were decreased by damage on the wafer surface. KOH treatment was used to remove the laser damage on the silicon surface prior to metalization of the front electrode by Ni/Cu/Ag plating. Ni and Cu were plated for each 4 minutes and 16 minutes and very thin layer of Ag with $1{\mu}m$ thickness was plated onto Ni/Cu electrode for 30 seconds to prevent oxidation of the electrode. The silicon solar cells with KOH treatment showed the 0.2% improved efficiency compared to those without treatment.

• Journal of the Korean Physical Society
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• 제80권
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• pp.698-716
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• 2022

Laser plasmas can be produced when high-power laser beams are focused in matter. A focused laser beam of TW(terawatt)-level high power has an extremely strong electric field, so neutral atoms are immediately ionized by the laser electric field, leading to a laser-produced plasma. The laser plasma can be produced by small table-top TW lasers based on the CPA (chirped-pulse amplification) technique, and now they are rather easily available even in university laboratories. In Korea, there are several CPA-based TW (or even petawatt) lasers in a few institutions, and they have been used for diverse laser plasma physics research and applications, including the laser acceleration for electrons and ions, high-power THz (tera-hertz) generation, advanced light sources, high-energy-density plasmas, plasma optics, etc. This paper reviews some of the laser plasma physics research and applications that have been performed in several universities and research institutes.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권5호
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• pp.303-308
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• 1999

Dielectric thin films of PLT(28) ($(Pb_{0.72}La_{0.28})Ti_{0.93}O_3$) have been deposited on $Pt/Ti/SiO_2/Si$ substrates in situ by a laser ablation. We have systematically changed the laser fluence from 0.4 J/$cm^2$ to 3 J/$cm^2$, and deposition temperature from $450^{\circ}C\; to\; 700^{\circ}C$. The surface morphology was changed from planar grain structure to columnar structure as the nucleation energy was increased. The PLT thin film with columnar structure showed good dielectric properties. The deposition temperature influenced on nucleation energy much stronger than the laser energy density did.

• Journal of Advanced Marine Engineering and Technology
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• 제31권5호
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• pp.567-574
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• 2007

Aluminum and aluminum alloys have high rate of lightness, recycling property and excellent specific strength. Fields using them have been widening because they ould satisfy both energy reduction and high efficiency in manufactures production. But they have many problems on welding due to high thermal conductivity and reflectivity, so the study to solve these problems ate proceeding actively around the world. This study was purposed to improve weldability and spread application range for aluminium alloys by using the unique property of aluminium which absorb high energy around $800{\mu}m$ wavelength and the higher temperature, the mote absorbtion of laser beam on preheating by multi-wavelength laser beam(pulsed Nd:YAG laser + diode laser with $808{\mu}m$ wavelength). The favorable mechanical properties were acquired by the test results of strength, hardness and leak of weld metal which had reduced its defect like crack and so on.

• 한국레이저가공학회지
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• 제14권4호
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• pp.9-13
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• 2011

The solar panel that consists of copper plate and copper tube was successfully welded by ultrasonic seam welding. However it was not only expensive the copper material but also ultrasonic welding has many problem such as high error rate, difficulty of dissimilar material welding, noise, etc. At this study, the laser welding of solar panel with aluminum plate instead of copper. The welding were carried out with the pulsed Nd:YAG laser and the weld bead geometry was measured with the variation of pulse energy. Consequently, there was no difference between the ultrasonic and the laser welding on the performance of heat transfer capacities. Also the formation of intermetalic compound such as CuAl2 was increased with the pulse energy.

• 한국정밀공학회지
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• 제14권1호
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• pp.142-149
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• 1997

Ceramic-coated anilox roll for printing is resistant to corrosion and wear, and hence has enhanced life and quality. Laser engraving is used typically for machining holes to store ink in this roll. Since engraved hole size and shape are directly related to laser processing parameters, it is necessary to know the rela- tionships among these parameters. In this study, the parameters for engraving of ;oasma sprayed ceramic coatings with Nd:YAG laser were studied. Relationships between hole shape and processing parameters were analyzed. Cr$_{2}$O$_{3}$ceramic was found to be most suitable for Nd:YAG laser engraving. It was found that hole depth can be increased by using higher energy pulses. Effect of using different assistant gases was small to the final results. For better results, it was suggested to use a very stable laser with shorter pulses and higher pulse energy.

• 한국생산제조학회지
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• 제22권4호
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• pp.643-651
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• 2013

This study applied a laser cleaning method (dry cleaning) that is used for cleaning semiconductor elements to dental implant cleaning. The lasers used in this study were pulsed fiber lasers with wavelengths of 1,064 and 532 nm. The peak output, energy per pulse, energy density per pulse, time of pulse experiment, and number of pulse experiments served as process variables for this study, and the variables were changed for each experiment. As a result, a laser with a wavelength of 532 nm showed much higher cleaning efficiency than its 1,064 nm counterpart. As the wavelength range decreased, the quantized energy increased and the reflection rate of the titanium used for the implant decreased; consequently, the energy absorption rate increased. Therefore, it is proposed that the energy density by wavelength has a greater influence on cleaning than does the output size.

• 한국광학회지
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• 제11권4호
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• pp.294-298
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• 2000

반도체레이저로 단면 여기시킨 Nd:VAP 레이저의 내부공진기 제2고조파 출력특성을 조사하였다. 유도방출 단면적과 형광수명의 곱이 커 낮은 발진문턱 특성을 갖는 Nd:S-VAP 매질은 컴팩트한 마이크로칩 레이저에 적합하다. 내부공진기를 이용한 제2고조파 발진문턱에너지가 81 uJ로 측정되어 쉽게 발진됨을 확인하였다. 여기에너지 $2\mu\textrm{J}$에서 제2고조파 에너지 $126\mu\textrm{J}$을 얻었고, 내부공진기 제2고조파의 출력을 계산하여 이론적인 해석 근거를 제시하였다. Q-스위치된 제2고조파 출력은 펄스폭 26ns에 펄스당 에너지 $15\mu\textrm{J}$로 저출력에서도 시.공간적으로 깨끗한 펄스를 얻었으며, $M^2$도 1.47로 우수한 빔 특성을 나타내었다.

• Current Photovoltaic Research
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• 제4권2호
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• pp.54-58
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• 2016

Laser-doped selective emitter process requires dopant source deposition, spin-on-glass, and is able to form selective emitter through SiNx layer by laser irradiation on desired locations. However, after laser doping process, the remaining dopant layer needs to be washed out. Laser-induced melting of pre-deposited impurity doping is a precise selective doping method minimizing addition of process steps. In this study, we introduce a novel scheme for fabricating highly efficient selective emitter solar cell by laser doping. During this process, laser induced damage induces front contact destabilization due to the hindrance of silver nucleation even though laser doping has a potential of commercialization with simple process concept. When the laser induced damage is effectively removed using solution etch back process, the disadvantage of laser doping was effectively removed. The devices fabricated using laser doping scheme power conversion efficiency was significantly improved about 1% abs. after removal the laser damages.

• Journal of Oral Medicine and Pain
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• 제22권1호
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• pp.15-22
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• 1997

In order to investigate the antibacterial effects of pulsed Nd:YAG Laser concerning to Streptococcus mutans, Streptococcus mutans was cultured and standardized and plated in 96 well plates. After that, black dye and chlorhexidine were applied and pulsed Nd:YAG Laser was irradiated to plates. Experimental groups which was applied with black dye and chlorhexidine were divided into 5 groups by concentration. And experimental groups and control group were subdivided as unlased and lased of 20, 40, and 60J. After laser irradiation, All groups were plated in agar plates and incubated for 18 hours. Bacterial colonies were counted and analysed comparitively, and the temperature of culture medium was measured on every laser irradiation. The results were obtained as follows; 1. In case of laser irradiation only, there is no significant reduction in number of Streptococcus mutans by irradiated energy of laser. 2. In case of black dye application, there is no difference by concentration of black dye but there is decrease when applied Laser and black dye simultaneously. 3. When applied chlorhexidine, the number of Streptococcus mutans was decreased according to increase of concentration, but there is no difference by irradiated energy of laser. 4. The temperature of culture medium was increased according to increase of irradiated energy of Laser, and the number of Streptococcus mutans was reduced remarkably just above 50 centigrade and killed above 70 centigrade. As above results, pulsed Nd:YAG Laser has well-absorbing affinity to black dye. And antibacterial effect of pulsed Nd:YAG Laser against Streptococcus mutans is seemed to be due to increase of temperature.