• 한국재료학회지
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• 제12권1호
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• pp.36-43
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• 2002

In this study, the nanosized ZnS thin films that can be used for fabrication of blue light-emitting diodes, electro-optic modulators, and n-window layers of solar cells were grown by the solution growth technique (SGT), and their surface morphology and film thickness and grain size dependence on the growth conditions were examined. Based on these results, the quantum size effects of ZnS were systematically investigated. Governing factors related to the growth condition were the concentration of precursor solution, growth temperature, concentration of aq. ammonia, and growth duration. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). With decreasing growth temperature and decreasing concentration of precursor solution, the surface morphology of film was found to be improved. Also, the film thickness depends largely on the ammonia concentration. In particular, this is the first time that the surface morphology dependence of ZnS film grown by SGT on the ammonia concentration is reported. The energy band gaps of samples were determined from the optical transmittance values, and were shown to vary from 3.69 eV to 3.91 eV. These values were substantially higher than 3.65 eV of bulk ZnS. It was also shown that the quantum size effect of SGT grown ZnS is larger than that of the ZnS films grown by most other growth techniques.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.65-70
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• 1998

The Spray-ICP technique uses the ICP(Inductively Coupled Plasma) of ultra-high temperature which is produced by r.f power. The ICP is well-kwown as a clean heat source for the preparation of pure ceramic particles because the ICP is a electrodeless-thermal plasma without contamination. In this study,{{{{ { SnO}_{2 } }}}} particles were sythesized from metal salt solution by Spray-ICP technique. The effects of concentration of solution, collecting location of powders were investicated. The prepared {{{{ { SnO}_{2 } }}}} particles from each concentration of solution had same crystalline phase(tetragonal {{{{ { SnO}_{2 } }}}}) a nd the mean size decreased in proportion to the increase of solution concentration. Each {{{{ { SnO}_{2 } }}}} p owders collector in reactor and electrostatic collector had same crystalline phase and morphologies. The mean size of {{{{ { SnO}_{2 } }}}} p articles prepared by Spray-ICP technique was below 30nm.

• 한국세라믹학회지
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• 제22권4호
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• pp.26-32
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• 1985

The subcritical crack growth of sintered SiC is investigated under various corrosive atmospheres such as distilled water Murakami solution and saturated KOH solution. The KI-V diagrams are obtained by the load relaxation method and incremental displacement rate method using the double torsion technique. The obtained fracture mechanics parameters (n) of sintered SiC are 79 in Murakami solution and 39 in saturated KOH solution. These data indicate that the subcritical crack growth of sintered SiC is taking place in these two conditions and the stress-corrosion cracking is suggested to be the mechanism. With these KI-V diagrams the life of sintered SiC in these conditions is predicted.

• 한국결정성장학회지
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• 제8권3호
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• pp.487-492
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• 1998

ICP(Inductively Coupled Plasma)를 열원으로 출발용액의 농도변화 및 $TiO_2$ 첨가로 $SnO_2$와 $(Sn,Ti)O_2$미분말을 합성하였으며 SnO2 박막을 제조하였다. 각각 합성된 $SnO_2$ 미분말은 모두 tetragonal의 rutile형으로서 입자들의 평균입경은 30nm로 매우 미세하였으며, 좁은 입도분포를 나타내었다. $TiO_2$를 첨가하였을 경우 $SnO_2-TiO_2$ 미분말은 고용체를 이루었으며, 첨가량이 증가함에 따라 결정성은 감소하였다. ICP tail flame으로 fused quartz 기판을 가열하여 (101)면을 주 peak로 하는 $SnO_2$ 박막을 얻었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.264.2-264.2
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• 2013

Molecular layer deposition (MLD) is sequential, self-limiting surface reaction to form conformal and ultrathin polymer film. This technique generally uses bifunctional precursors for stepwise sequential surface reaction and entirely organic polymer films. Also, in comparison with solution-based technique, because MLD is vapor-phase deposition based on ALD, it allows epitaxial growth of molecular layer on substrate and is especially good for surface reaction or coating of nanostructure such as nanopore, nanochannel, nanwire array and so on. In this study, polyurea film that consisted of phenylenediisocyanate and phenylenediamine was formed by MLD technique. In situ Fourier Transform Infrared (FTIR) measurement on high surface area SiO2 substrate was used to monitor the growth of polyurethane and polyurea film. Also, to investigate orientation of chemical bonding formed polymer film, plan-polarized grazing angle FTIR spectroscopy was used and it showed epitaxial growth and uniform orientation of chemical bones of polyurea films.

• 대한수학회논문집
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• 제31권4호
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• pp.869-878
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• 2016

This paper presents an ecient fractional shifted Legendre polynomial method to solve the fractional Volterra's model for population growth model. The fractional derivatives are described based on the Caputo sense by using Riemann-Liouville fractional integral operator. The theoretical analysis, such as convergence analysis and error bound for the proposed technique has been demonstrated. In applications, the reliability of the technique is demonstrated by the error function based on the accuracy of the approximate solution. The numerical applications have provided the eciency of the method with dierent coecients of the population growth model. Finally, the obtained results reveal that the proposed technique is very convenient and quite accurate to such considered problems.

• 한국환경보건학회지
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• 제36권4호
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• pp.337-341
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• 2010

The modified simultaneous differential staining technique, which enables double staining of cartilage and bones, needs to be improved to prevent soft tissues from being damaged during the staining process. Key factors influencing the extent to which soft tissues are damaged include the fixative used, macerating time, potassium hydroxide concentration, incubation temperature and the removal of skin from specimens. Here we describe a protocol that enables the hardening of tissues during bleaching and maceration. We also describe a method for objectively measuring rates of cartilage and bone growth. The use of formalin as a fixative rendered soft tissues more rigid due to the resulting chemical bonds formed between proteins. Blotted specimens were immersed in 1% potassium hydroxide (KOH) and incubated at $37^{\circ}C$ for 1 day (smaller specimens) or 2-3 days (larger specimens). The 1% KOH solution was also used as the diluent solution for the subsequent immersion in a graded series of 30%, 50%, 70%, 90%, 100% glycerol solutions, a procedure that made soft tissues even more transparent and hardened. It was not necessary to remove the skin of specimens shorter than 2 cm, since the macerating solution could easily penetrate their thin skin layer and continuously remove those pigments hindering visibility. Since excessive osmosis is another factor that can damage soft tissues in the macerating process by causing the rupture of those cells not able to withstand the osmotic pressure, here it was minimized by balancing the salt concentration between the interior and exterior of cells with the addition of 0.9% sodium chloride (NaCl) in the macerating solution. Finally, to determine the proportions of cartilage and bone growth, photographs of the stained specimens were taken with a dissecting microscope and sections corresponding to the cartilage and bones were cut out from the printed pictures and weighed. Our results show that this method is suitable for the objective evaluation of bone and cartilage growth.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.149-155
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• 1997

We have successfully grown colorless and transparent Rb-doped potassium niobate (KRN) single crystals using the top seeded solution growth(TSSG) technique. In our crystal growth experiments, the Rb doping concentrations within the melt range from 2-15 mol% relative to that of Nb$_2$O5. Atomic absorption measurements indicate that the Rb content in the KRN solid solution is rather low; the Rb segregation coefficient is found to be on the order of 0.05. It is believed that this is due to the relatively much larger Rb+ ionic radius compared to that of K+, rendering it more difficult for Rb to replace K in the KNbO$_3$(KN) host lattice. Preliminary single-pass second harmonic generation (SHG) experimental results indicate that there exists marginal improvement in the phase-matching temperature tolerance of KRN compared to that of pure Kn single crystals.

• 한국결정성장학회지
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• 제10권3호
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• pp.199-204
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• 2000

본 연구에서는 청색 발광다이오드, 광전모듈레이터, 태양전지의 창문층 등의 광범위한 응용분야를 갖는 ZnS를 용액 성장법에 의해 nanometer 사이즈의 입자로 구성된 박막의 형태로 슬라이드 유리기판에 성장하고 구조적, 광학적 특성을 분석하고, 이 결과를 토대로 ZnS박막의 양자사이즈효과에 대해 연구하였다. 성장조건에 관련된 인자는 precursor 용액의 농도, 성장온도, 암모니아 용액의 농도, 성장시간 등이었다. X-선 회절분석 결과, 본 연구에서 용액성장법으로 성장한 ZnS박막은 cubic 구조($\beta$-ZnS)를 가졌다. 성장온도가 $75^{\circ}C$일 때 막의 표면상태가 가장 양호했으며 입자사이즈의 균일도도 가장 우수했다 광에너지 변화에 따른 광투과도 측정 결과, 본 연구의 ZnS 시료는 성장조건을 조절함에 따라 에너지밴드갭이 3.69 eV~3.91 eV까지 조절 할 수 있었고, 이는 벌크 ZnS의 에너지밴드갭인 3.65 eV보다 훨씬 높은 수치로서 양자사이즈효과에 의한 blue-shift 현상이 용액성장법으로 합성된 ZnS에서 큰 폭으로 나타남을 알 수 있었다. 그리고 photoluminescence(PL)측정 결과, ZnS 입자의 미세성으로 인한 입자 표면준위의 영향으로 PL 피크가 에너지밴드갭보다 훨씬 적은 에너지 영역에서 발생했다. 특히 PL피크의 위치가 입자사이즈와 막두께에 따라 shift했는데, 이는 용액성장법으로 성장한 ZnS의 경우 본 연구에서 최초로 보고되는 것이다.

• 한국결정성장학회지
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• 제14권4호
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• pp.174-186
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• 2004

Striations are growth-induced inhomogeneities which hamper the applications of solid-solution crystals and of doped crystals in numerous technologies. Thus the optimized performance of solid solutions often can not be exploited. The inhomogeneity problem can be solved in specific cases by achieving a distribution coefficient one in growth from melts and from solutions. Macrostep-induced striations can be suppressed by controlling the growth mode, by achieving growth on facets thereby preventing step bunching. Thermal striations are commonly assumed to be caused by convective instabilities so that reduced convection by microgravity or by damping magnetic fields was and is widely attempted to reduce such inhomogeneities. Here it will be shown that temperature fluctuations at the growth interface cause striations, and that hydrodynamic fluctuations in a quasi-isothermal growth system do not cause striations. The theoretically derived conditions were experimentally established and allowed the growth of striation-free crystals of $KTa_{1-x}Nb_xO_3$"KTN" solid solutions. Hydrodynamic variations from the accelerated crucible rotation technique ACRT did not cause striations as long as the temperature was controlled within $0.03^{\circ}$ at $1200^{\circ}C$ growth temperature. Alternative approaches to solve or reduce the segregation and striation problems in growth from melts and from solutions are discussed as well.