• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.496-498
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• 2005

We reported that high dielectric hafnium oxide nano-film deposited by thermal atomic layer deposition on the poly-silicon film (poly-Si). The poly -Si film was produced by plasma enhanced chemical vapor deposition and excimer laser annealing. We used the hafniu m chloride ($HfCl_4$) and water as the precursors and analyzed the hafnium oxide film by transmission electron microscope and secondary ion mass spectrometer. Hafnium oxide produced by the ALD method showed very good coverage on the rough surface of poly-Si film. While deposited with 200 cycles, these hafnium oxide films revealed a relatively smooth surface and good uniformity, but the cumulative roughness produced by the incomplete reaction was apparent when the amount of deposition cycle increased to 600 cycles.

• Bulletin of the Korean Chemical Society
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• 제18권10호
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• pp.1076-1082
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• 1997

The infrared, Raman, and jet-cooled laser-induced fluorescence excitation spectra of 1,2,3,4-tetrahydronaphthalene have been recorded and analyzed. The observed vibrations have been assigned to understand the conformational behaviors in its electronic ground (S0) and excited (S1) states. Ab initio at the HF/6-31G** level and molecular mechanics (MM3) force field calculations have been carried out to generate the complete normal mode frequencies of the molecule in its S0 state. The vibrational frequencies calculated from the ab initio method show a better agreement with the observed infrared and Raman frequencies than those calculated from the MM3 method. In several cases, the normal mode calculations were very helpful to clarify some ambiguities of previous assignments. In addition, the ring inversion process between two twisted conformers of 1,2,3,4-tetrahydronaphthalene has been reexamined utilizing ab initio calculation. The results show that the ring inversion energy is in the range of 3.7-4.3 kcal/mol which is higher than the previously reported AM1 value of 2.1 kcal/mol.

• Bulletin of the Korean Chemical Society
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• 제16권4호
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• pp.341-344
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• 1995

Laser-induced fluorescence (LIF) excitation spectra were measured for fluorene (FR) cooled in pulsed supersonic expansions of He in the range 283.7-296.7 nm. Ab initio studies of FR have also been carried out for determining the electronic and vibrational structures by using the standard 3-21G basis sets. In the LIF excitation spectra of FR, highly resolved vibronic bands are observed having the band origin of 33,791 cm-1. The vibrational bands above the electronic origin were assigned on the basis of the well-characterized electronic vibrational bands reported previously and of normal modes of vibrations derived by our HF/3-21G calculations.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.339-339
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• 2012

지난 몇 년 동안, 투명 비정질 산화물 반도체는 유기 발광 다이오드, 플렉서블 전자 소자, 솔라 셀, 바이오 센서 등 많은 응용분야에 연구되고 있다. 투명 비정질 산화물 반도체 그룹들 중, 특히 비정질 IGZO 박막 트랜지스터는 비정질 상태임에도 불구하고 높은 이동도와 낮은 동작 전압으로 훌륭한 소자 특성을 보인다. 이러한 고성능의 IGZO 박막 트랜지스터는 RF 마그네트론 스퍼터링이나 pulsed laser deposition과 같은 고진공 장비를 이용하여 이미 여러 그룹에서 제작되고 발표되었다. 하지만 진공 증착 시스템은 제조 비용의 절감이나 디스플레이 패널의 대면적화에 큰 걸림돌이 되고 있고, 이러한 문제점을 극복하기 위해서 용액 공정은 하나의 해결책이 될 수 있다. 용액 공정의 가장 큰 장점으로는 저온 공정이 가능하기 때문에 글라스나 플라스틱 기판에서 대면적으로 제작할 수 있고 진공 장비가 필요없기 때문에 제조 비용을 획기적으로 절감시킬 수 있다. 본 연구에서는 high-k 게이트 절연막과 IGZO 채널 층을 용액 공정을 이용하여 박막 트랜지스터를 제작하고 그에 따른 전기적 특성을 분석하였다. IGZO의 몰 비율은 In, Ga, Zn 순으로 각각 0.2 mol, 0.1 mol, 0.1 mol로 제작하였고, high-k 게이트 절연막으로는 Al2O3, HfO2, ZrO2을 제작하였다. 또한, 용액 공정 IGZO TFT를 제작하기 전, 용액 공정 high-k 게이트 절연막 캐패시터를 제작하여 그 특성을 분석하였다. 다양한 용액 공정 high-k 게이트 절연막 중, 용액공정 HfO2를 이용한 IGZO TFT는 228.3 [mV/dec]의 subthreshold swing, 18.5 [$cm^2/V{\cdot}s$]의 유효 전계 이동도, $4.73{\times}106$의 온/오프 비율을 보여 매우 뛰어난 전기적 특성을 확인하였다.

• 분석과학
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• 제20권3호
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• pp.219-226
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• 2007

유리 같은 미세 증거물은 전이(transfer)의 결과로서 법과학 실험실에 자주 제시되는 증거물의 일종이다. 이들 시료에서 미량 원소 분석의 반복성과 재현성을 검토하였다. 미세 증거물의 유출원을 규명하기 위하여 LA-ICP-MS를 사용하여 분산 분석이 이루어졌다. 짝지음비교가 모든 시료에 대하여 이루어졌고 각 시료는 이동식별을 위하여 총 [n(n-1)/2] (n :시료의 수) 쌍이 비교 되었다. 이번 실험의 목적은 법과학 시료의 다원소분석에 대한 LA-ICP-MS의 이용 가능성을 검토하는 것이다. 유리의 경우, 2개의 제조 공장으로 부터의 12개 시료를 수집하여 분석에 사용하였다. 유리에서 미량원소 분석용 표준품 NIST 612를 사용하여 31개 원소를 분석하고 분산분석(ANOVA)이 수행되었다. 원소들은 정밀도와 시료간 분산값을 고려 하여 4개의 그룹으로 나뉘어 졌다. 11개의 원소(209Bi, 90Zr, 121Sb, 178Hf, 59Co, 238U, 208Pb, 140Ce, 118Sn, 49Ti, 137Ba)가 선택 되었고 137Ba 만으로 66개의 가능한 pair들 중 6개를 구별(p<0.05)하지 못하였으나, 49Ti과 137Ba의 두 원소를 사용할 경우 모든 시료들이 구별 가능 한 것으로 나타났다(p<0.05). 결론적으로 LA-ICP-MS에 의한 다원소 분석은 법과학 시료의 이동 식별에 잠재력있는 분석기법이라 하겠다.

• 센서학회지
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• 제8권2호
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• pp.184-188
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• 1999

Pulsed laser deposition법에 의하여 양질의 PbTe 박막을 다양한 기판온도에 따라 성장시켰다. XRD패턴으로 부터 각 온도에서의 PbTe층들은 결정화가 되어있음을 알 수 있었다. 또한 PbTe 박막의 XRD 피크들은 (h00)의 방향성을 나타내고 있다. Pb의 재증발로 인하여 $400^{\circ}C$이상에서는 PbTe 박막은 결정성의 박막으로 형성되지 않았다. AFM 이미지로부터 박막의 표면은 작은 granular 결정들과 평탄한 매트릭스로 구성되어 있음이 관찰되었다. 기판온도의 증가에 따라 표면의 입자들이 커지는 것을 알 수 있었다. Hall-effect 측정으로부터 $300^{\circ}C$에서 성장한 PbTe 박막의 전기적 특성은 $3.68{\times}10^{18}cm^{-3}$의 캐리어 농도와 $148\;cm^2/Vs$의 Hall 이동도를 나타내었다.

• 대한소아치과학회지
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• 제23권3호
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• pp.640-658
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• 1996

The purpose of this study was to examine the mechanism of improving acid resistance of Nd-YAG laser irradiated tooth enamel and determine the most effective energy density for improving acid resistance. The bovine tooth enamel were lased with a pulsed Nd-YAG laser. The energy densities of exposed laser beam were varied from 10 to $70\;J/cm^2$. To investigate the degree of improving acid resistance by irradiation, all the samples were submerged to demineralize in 0.5 N $HClO_4$ solution for 1 minute. After 1 minute, 0.05 % $LaCl_3$ was added to the solution for interrupting the demineralization reaction. The amounts of dissolved calcium and phosphate in the solution were measured by using an atomic absorption spectrophotometer and the UV/VIS spectrophotometer, respectively. To examine the mechanism of improving acid resistance, X-ray diffraction analysis, infrared spectroscopy, and scanning electron microscopy were taken. The X-ray diffraction pattern of the samples were obtained in the $10^{\circ}{\sim}80^{\circ}2{\theta}$ range with $Cu-K{\alpha}$ radiation using M18HF(Mac Science Co.) with X-ray diffractometer operating at 40 KV and 300 mA. The infra-red spectra of the ground samples in 300 mg KBr pellets 10 mm diameter were obtained in the $4000cm^{-1}\;to\;400cm^{-1}$ range using JASCO 300E spectrophotometer. The scanning electron microscopy was carried out using JSM6400(JEOL Co.) with $500{\sim}2000$ times magnification. The results were as follow 1. The concentration of calcium dissolved from laser irradiated enamel with $50J/cm^2$ was significantly lesser than that of unlased control group (p<0.05) 2. From the result of the X-ray diffraction analysis, $\beta$-TCP, which increases acid solubility, was identified in lased enamel but the diffraction peaks of (002) and (004) became sharp with increasing energy density of laser irradiation. This means that the crystals in lased samples were grown through the c-axis and subsequently, the acid solubility of enamel decreased. 3. The a-axis parameter was slightly increased by laser irradiation, whereas the c-axis parameter was almost constant except for a little decrease at $50J/cm^2$. 4. In the infra-red spectra of lased enamels, phosphate bands ($600{\sim}500cm^{-1}$), B-carbonate bands (870, $1415{\sim}1455cm^{-1}$), and A-carbonate band ($1545cm^{-1}$) were observed. The amounts of phosphate bands and the B-carbonate bands were reduced, on the other hand, the amount of the A-carbonate band was increased by increase the energy density. 5. The SEM experiments reveal that the surface melting and recrystallization were appeared at $30J/cm^2$ and the cracks were observed at $70J/cm^2$. From above results, It may be suggested that the most effective energy density for improving acid resistance of tooth enamel with the irradiation of Nd-YAG laser was $50J/cm^2$. The mechanism of improving acid resistance were reduction of permeability due to surface melting and recrystallization of lased enamel and reduction of acid solubility of enamel due to decrease of carbonate content and growth of crystal.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권8호
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• pp.451-454
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• 2000

We have grown vertically aligned carbon nanotubes in a large area of Co-Ni codeposited Si substrates by the thermal CVD usign $C_2H_2$ gas. Since the discovery of carbon nanotubes, growth of carbon nanotubes has been achieved by several methods such as laser vaporization, arc discharge, and pyrolysis. In particular, growth of vertically aligned nanotubes is important to flat panel display applications. Recently, vertically aligned carbon nanotubes have been grown on glass by PECVD. Aligned carbon nanotubes can be also grown on mesoporous silica and Fe patterned porous silicon using CVD. In this paper, we demonstrate that carbon nanotubes can be vertically aligned on catalyzed Si substrate when the domain density of catalytic particles reaches a certain value. We suggest that steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically and each nonotubes are grown in bundle.

• 한국표면공학회지
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• 제50권5호
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• pp.315-321
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• 2017

Antireflective pyramid arrays can be readily obtained via anisotropic etching in alkaline solution (KOH, NaOH), which is widely used in crystalline-Si (c-Si) solar cells. The periodic inverted pyramid arrays show even lower light reflectivity because of their superior light-trapping characteristics. Since this inverted pyramidal structures are mostly achieved using very complex techniques such as photolithograpy and laser processes requiring extra costs, here, we demonstrate the Cu-nanoparticle assisted chemical etching processes to make the inverted pyramidal arrays without the need of photolithography. We have mainly controlled the concentration of $Cu(NO_3)_2$, HF, $H_2O_2$ and temperature as well as time factors that affecting the reaction. Optimal inverted pyramid structure was obtained through reaction parameters control. The reflectance of inverted pyramid arrays showed < 10% over 400 to 1100 nm wavelength range while showing 15~20% in random pyramid arrays.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.280-284
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• 2004

Multicrystalline silicon wafers were textured in an alkaline bath, basically using sodium hydroxide and in acidic bath, using mainly hydrofluoric acid (HF), nitric acid $(HNO_3)$ and de-ionized water (DIW). Some wafers were also acid polished for the comparative study. Comparison of average reflectance of the samples treated with the new recipe of acidic solution showed average diffuse reflectance less than even 5 percent in the optimized condition. Solar cells were thus fabricated with the samples following the main steps such as phosphorus doping for emitter layer formation, silicon nitride deposition for anti-reflection coating by plasma enhanced chemical vapor deposition (PECVD) and front surface passivation, screen printing metallization, co-firing in rapid thermal processing (RTP) Furnace and laser edge isolation and confirmed >14 % conversion efficiency from the best textured samples. This isotropic texturing approach can be instrumental to achieve high efficiency in mass production using relatively low cost silicon wafers as starting material.