• E2M - 전기 전자와 첨단 소재
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• 제9권3호
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• pp.298-303
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• 1996

A double diffusion technique is developed to enhance the effective mode index of optical waveguides in $LiTaO_3$. It consists of Zn diffusion from the vapor phase at relatively low temperatures (750->$800^{\circ}C$), into waveguides initially produced by Ti indiffusion at higher temperature (1150->$1200^{\circ}C$). Both X- and Z-cut substrates are investigated. A model that combines profiles of both diffusion is formulated to calculate the expected effective index values for planar waveguides. Good agreement is found between experimental results and model predictions which assume that the initial Ti profile is not affected by the lower temperature Zn diffusion. Effective index enhancements as high as 0.005 and 0.003 are obtained by this method for the fundamental extraordinary and ordinary modes, respectively.

• 한국진공학회지
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• 제13권3호
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• pp.109-113
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• 2004

InP에서 열처리 온도와 시간 및 활성화 온도에 따른 Zn의 확산의 특성을 electrochemical capacitance-voltage 법으로 조사하였다. InP층은 metal organic chemical vapor deposition를 이용하여 성장하였으며, 화산방법으로는 $Zn_3P_2$ 확산과 박막과 rapid thermal annealing를 사용하였다. 최대의 정공 농도를 갖는 p-lnP 층은 $550^{\circ}C$에서 5분 동안 확산과 활성화를 한 시료에서 얻었고, Zn의 농도는 $1\times10^{19}\textrm{cm}^{-3}$이었다. $550^{\circ}C$에서 5-20 분 동안 확산을 수행한 결과 정공농도의 확산 깊이는 1.51 $\mu\textrm{m}$에서 3.23 $\mu\textrm{m}$로 이동하였고, Zn의 확산계수는 $5.4\times10^{-11}\textrm{cm}^2$/sec이었다. 활성화 시간의 증가로, Zn가 더 깊게 확산하지만, 정공농도는 거의 변화가 없었다. 이는 도핑된 영역의 과잉의 침입형 Zn가 도핑되지 않은 영역으로 빠르게 확산하고 치환형 Zn로 변한다는 것을 의미한다. 정공농도는 $SiO_2$ 박막의 두께가 1,000$\AA$ 이상이어야 안정적으로 분포된다.

• Transactions on Electrical and Electronic Materials
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• 제9권1호
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• pp.24-27
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• 2008

ZnO has intensively attracted interest for the next generation of short wavelength LEDs and semiconductor lasers. However, for the development and application of the devices based on this material, the fabrication of p-type ZnO thin films is pivotal. Generally, the process of preparation of ZnO is unavoidably accompanied by the natural donor ions such as interstitial Zn ions and oxygen vacancy ions that show n-type electrical property and make fabrication of p-type ZnO to be a hard problem. On this study, to realize stable high-quality p-type ZnO thin films, the undoped ZnO thin films were diffused with P in vapor state. The ZnO:P thin films showed high-quality p-type properties electrically and optically.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.371-375
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• 2014

Diffusion coefficient of Fe in polycrystalline host ZnSe as a mid-IR gain medium has been measured in the annealing temperature ranges of 850 to $950^{\circ}C$. The synthesis of the samples was carried out in quartz ampoule in which the Fe thin film deposited by physical vapor evaporation method on the ZnSe. One can realize that the diffusion coefficient strongly depends on the surface active surfactants through the cleaning process and the substrate temperature during the thin film deposition leading to $2.04{\times}10^{-9}cm^2/s$ for $Fe^{2+}:ZnSe$. The Annealing temperature dependence of the Fe ions diffusion in ZnSe was used to evaluate the activation energy, $E_a$=1.39 eV for diffusion and the pre-exponential factor $D_0$ of $13.5cm^2/s$.

• 한국재료학회지
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• 제12권4호
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• pp.304-307
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• 2002

A zinc oxide (ZnO) single crystal was used as a substrate in the hydride vapor-phase epitaxy (HVPE) growth of GaN and the structural and optical properties of GaN layer were characterized by x- ray diffraction, transmission electron microscopy, secondary ion mass spectrometry, and photoluminescence (PL) analysis. Despite a good lattice match and an identical structure, ZnO is not an appropriate substrate for application of HVPE growth of GaN. Thick film could not be grown. The substrate reacted with process gases and Ga, being unstable at high temperatures. The crystallinity of ZnO substrate deteriorated seriously with growth time, and a thin alloy layer formed at the growth interface due to the reaction between ZnO and GaN. The PL from a GaN layer demonstrated the impurity contamination during growth possibly due to the out-diffusion from the substrate.

• 한국전기전자재료학회논문지
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• 제27권2호
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• pp.71-75
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• 2014

To observe the optical characteristic of oxide semiconductor depending on the degree of bonding structures, SiOC, ZnO and IGZO were prepared by the RF magnetron sputter system and chemical vapor deposition. Generally, crystal ZnO, amorphous SiOC and IGZO changed the optical characteristics in according to the electro-chemical behavior due to the oxygen vacancy at an interface between different groups. Transmittance of SiOC and IGZO with amorphous structures was higher than that of ZnO with crystal structure, because of lowering the carrier concentration due to the recombination of electron and holes carriers as oxygen vacancies. Besides, the energy gap of amorphous SiOC and IGZO was higher than the energy gap of crystal ZnO. The diffusion mobility of holes is higher than the drift mobility of electrons.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.50.1-50.1
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• 2009

Transparent conductive oxides (TCOs) play an important role in thin-film solar cells in terms of low cost and performance improvement. Al-doped ZnO (AZO) is a very promising material for thin-film solar cellfabrication because of the wide availability of its constituent raw materials and its low cost. In this study, AZO films were prepared by low pressurechemical vapor deposition (LPCVD) using trimethylaluminum (TMA), diethylzinc(DEZ), and water vapor. In order to improve the absorbance of light, atypical surface texturing method is wet etching of front electrode using chemical solution. Alternatively, LPCVD can create a rough surface during deposition. This "self-texturing" is a very useful technique, which can eliminate additional chemical texturing process. The introduction of a TMA doping source has a strong influence on resistivity and the diffusion of light in a wide wavelength range.The haze factor of AZO up to a value of 43 % at 600 nm was achieved without an additional surface texturing process by simple TMA doping. The use of AZO TCO resulted in energy conversion efficiencies of 7.7 % when it was applied to thep-i-n a-Si:H thin film solar cell, which was comparable to commercially available fluorine doped tin oxide ($SnO_2$:F).

• 센서학회지
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• 제29권6호
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• pp.420-426
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• 2020

A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO₂ nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO₂ seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO₂ seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.

• 한국결정성장학회지
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• 제14권5호
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• pp.226-232
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• 2004

One predicts the crystal growth rate of ZnSe with a low vapor pressure system in a horizontal configuration based on one dimensional advection-diffusion and two-dimensional diffusion-convection model. The present results show that for the ratios of partial pressures, s = 0.2 and 2.9, the growth rate increases with the temperature differences between the source and crystal. As the ratio of partial pressure approaches the stoichiometric value, s = 2 from s = 1.5 (zinc-deficient case: s < 2) and 2.9 (zinc-rich case: s > 2), the rate increases sharply. For the ranges from 1.5 to 1.999 (zinc-deficient case: s < 2) and from s = 9 to 2.9 (zinc-rich case: s > 2), the rate are slightly varied. From the viewpoint of the order of magnitude, the one-dimensional model for low vapor pressure system falls within the 2D predictions, which indicates the flow fields would be advective-diffusive. For the effects of gravitational accelerations on the rate, the gravitational constants are varied from 1 g to $10^{-6}$ g for $\Delta$T = 50 K and s = 1.5, the rates remain nearly constant, i.e., 211 mg/hr, which indicates Stefan flow is dominant over convection.

• 한국표면공학회지
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• 제46권3호
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• pp.116-119
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• 2013

To improve the corrosion resistance of an electrogalvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at $250-330^{\circ}C$. The zinc-magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at $270-310^{\circ}C$ showed better corrosion resistance than others. In X-ray diffraction analysis, $ZnMg_2$ was detected through out the temperature range, whereas $Mg_2Zn_{11}$ and $FeZn_{13}$ were detected only in the film annealed at $310^{\circ}C$. The depth composition profile showed that the compositions of Mg at $270-290^{\circ}C$ are evenly and deeply distributed in the film surface layer. These results demonstrate that $270-290^{\circ}C$ is a proper temperature range to produce a layer of $MgZn_2$ intermetallic compound to act as a homogeneous passive layer.