• Korean Journal of Materials Research
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• v.10 no.7
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• pp.482-488
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• 2000

The deposition characteristics of Cu film by MOCVD using (hfac)Cu(1,5-COD)(1,1,1,5,5,5-hexafluro-2,4-pentadionato Cu(I) 1,5-cryclooctadiene) as a precursor have been investigated in terms of substrate conditions. Two different substrates such as air-exposed TiN and non-contaminated TiN were used for the MOCVD of Cu. MOCVD of Cu on the air-exposed TiN affected the nucleation rate of Cu as well as its growth, resulting in the Cu films having poor interconnection between particles with relatively small grains. On the other hand, in-situ MOCVD of Cu led to the Cu films having a significantly improved interconnection between particles with larger grains, indicating the resistivity as low as $2.0{\mu}{\Omega}-cm$ for the films having more than 1900$\AA$ thickness. Moreover, better adhesion of Cu films to the TiN by using in-situ MOCVD has been obtained. Finally, initial coalescence mechanism of Cu was suggested in this paper in terms of different substrate conditions by observing the surface morphology of the Cu films deposited by MOCVD.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.283-291
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• 2011

Polymer electrolyte membrane fuel cells (PEMFCs) use the bipolar plate of various materials between electrolyte and contact electrode for the stable hydrogen ion exchange activation. The bipolar plate of various materials has representatively graphite and stainless steel. Specially, stainless steels have advantage for low cost and high product rate. In this study, SUS 316 was effectively coated with 600 nm thick F-doped tin oxide (SnOx:F) by electron cyclotron resonance-metal organic chemical vapor deposition and investigated in simulated fuel cell bipolar plates. The results showed that an F-doped tin oxide (SnOx:F) coating enhanced the corrosion resistance of the alloys in fuel cell bipolar plates, though the substrate steel has a significant influence on the behavior of the coating. Coating SUS 316 for fuel cell bipolar plates steel further improved the already excellent corrosion resistance of this material. After coating, the increased ICR values of the coated steels compared to those of the fresh steels. The SnOx:F coating seems to add an additional resistance to the native air-formed film on these stainless steels.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.363-364
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• 2012

기존 양자점에 대한 연구는 레이저 다이오드와 광증폭기등과 같은 광소자의 활성층에 사용되던 양자우물을 대체하기 위하여 고밀도, 고균일 양자점 성장에 관한 연구가 활발히 진행되었지만, 최근에는 양자점을 이용한 Single-photon source의 관심이 높아짐에 따라 저밀도 양자점 성장에 관한 연구가 주목 받고 있다. 본 연구에서는 수직형 저압 Metal organic chemical vapor deposition (MOCVD)를 이용하여 InP 기판 위에 저밀도 InAs 양자점을 성장하였다. 저밀도의 양자점을 성장하기 위하여 양자점과 덮개 층($1.1 {\mu}m$ InGaAsP)사이에 V족 원료 가스인 As만 공급하는 성장 중단 시간 (GI:Growth interruption)을 삽입하였다. 시료의 구조는 InP (100)기판위에 50 nm InGaAsP barrier, 1.5ML GaAs를 성장 후 InAs 1.9 ML를 성장하였다. 그 후 0, 1, 2, 5 분의 GI을 삽입한 후 InGaAsP 와 InP 덮개층을 성장하였다. 양자점의 밀도와 형상을 측정하기 위하여 Atomic force microscopy (AFM)을, 광학적 특성 분석을 위하여 저온 Micro Photoluminescence (${\mu}$-PL)을 측정하였다. 성장 중단 시간의 증가에 따라 InAs/InP 양자점의 높이와 넓이는 증가하고 밀도는 감소하였다. 성장 중단 시간 3분 이후에는 밀도 감소가 둔화 되었으며, 5분일 때 $3.2{\times}10^7/cm^2$의 극저밀도 InAs/InP 양자점이 성장되었다. 또한 저밀도 양자점 시료의 저온 ${\mu}$-PL을 측정하여 단일 양자점의 exciton과 bi-exciton peak가 측정되었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.1
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• pp.1-6
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• 2020

In this research, 50 nm thick AlN thin films were deposited on the patterned sapphire (0001) substrate by using HVPE (Hydride Vapor Phase Epitaxy) system and then epitaxial layer structure was grown by MOCVD (metal organic chemical vapor deposition). The surface morphology of the AlN buffer layer film was observed by SEM (scanning electron microscopy) and AFM (atomic force microscope), and then the crystal structure of GaN films of the epitaxial layer structure was investigated by HR-XRC (high resolution X-ray rocking curve). The XRD peak intensity of GaN thin film of epitaxial layer structure deposited on AlN buffer layer film and sapphire substrate was rather higher in case of that on PSS than normal sapphire substrate. In AFM surface image, the epitaxial layer structure formed on AlN buffer layer showed rather low pit density and less defect density. In the optical output power, the epitaxial layer structure formed on AlN buffer layer showed very high intensity compared to that of the epitaxial layer structure without AlN thin film.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.557-565
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• 2014

We report the effect of basal-plane stacking faults (BSFs) on X-ray diffraction (XRD) of non-polar (11$\underline{2}$0) a-plane GaN films with different $SiN_x$ interlayers. Complete $SiN_x$ coverage and increased three-dimensional (3D) to two-dimensional (2D) transition stages substantially reduce BSF density. It was revealed that the Si-doping profile in the Si-doped GaN layer was unaffected by the introduction of a $SiN_x$ interlayer. The smallest in-plane anisotropy of the (11$\underline{2}$0) XRD ${\omega}$-scan widths was found in the sample with multiple $SiN_x$ layers, and this finding can be attributed to the relatively isotropic GaN mosaic resulting from the increase in the 3D-2D growth step. Williamson-Hall (WH) analysis of the (h0$\underline{h}$0) series of diffractions was employed to determine the c-axis lateral coherence length (LCL) and to estimate the mosaic tilt. The c-axis LCLs obtained from WH analyses of the present study's representative a-plane GaN samples were well correlated with the BSF-related results from both the off-axis XRD ${\omega}$-scan and transmission electron microscopy (TEM). Based on WH and TEM analyses, the trends in BSF densities were very similar, even though the BSF densities extracted from LCLs indicated that the values were reduced by a factor of about twenty.

• Journal of Korean Vacuum Science & Technology
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• v.4 no.1
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• pp.23-26
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• 2000

We have fabricated by metal organic chemical vapor deposition (MOCVD) In$\_$0.13/Ga$\_$0.87/N/GaN multiple quantum well (MQW) with thickness as thin as 10 A and barriers also of th same width on (0001) sapphire substrate. We have investigated this thin MQW by steady-state and time-resolved photoluminescence(PL) in picosecond time scale in a wide temperature range from 10 to 290 K. In the PL at 10 K, we observed a broad peak at 3.134 eV which was attributed to the quantum well emission of InGaN. The full width at half maximum (FWHM) of this peak was 129 meV at 10 K and its broadening at low temperatures was considered to be due to compositional fluctuations and interfacial disorder in the alloy. The narrow width of the quantum well was mainly responsible for the broadening of the emission linewidth. We also observed an intense and sharp peak at 3.471 eV of GaN barrier. From the temperature dependent PL measurements, the activation energy of the InGaN quantum well emision peak was estimated to be 69 meV. The lifetime of the quantum well emission was found to be 720 ps at 10 K, which was explained in terms of the exciton localization arising from potential fluctuations.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.857-864
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• 2018

Demand for developing artificial green pearl that meets the needs of modern people has been increasing. In this paper, eco-friendly inorganic pearlescent pigment was used instead of organic pigment and urethane resin was substituted for nitrocellulose which has been used as main materials in previous preparation method, increasing gloss from 73.4% to 86.7%. Urethane was coated on substrate before finishing with CVD, resulting high gloss of 96%. Colorimeteric analysis shows that a* and b* of CIE value was changed from +37.7 and +24.5 to +31.9 and +14.2 respectively because of CVD finishing, obtaining colorful, high gloss and durable artificial pearl. Quality and toxicity of samples was established by chemical resistance, glossiness, colorimeter, surface roughness, wear resistance, content of heavy-metal, and salt water test.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.333-336
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• 2007

A Strained Layer Multiquantum-Well (SL-MQW) distributed feedback laser at a wavelength of 1.31 um operating from $-40^{\circ}C$ to $85^{\circ}C$ without any cooling is grown by metal-organic chemical vapor deposition (MOCVD). Lasers with high slope efficiency are achieved through careful optimization of a SL-MQW active layer, especiallyoptimizing the amount of strain, the well thickness, the barrier thickness, the number of wells, and the active layer width. In this paper, we obtain the slope efficiencies of 0.38[mW/mA] and 0.26 [mW/mA] at $25^{\circ}C$ and $85^{\circ}C$, respectively. Threshold currents are 7.1[mA] and 19.8[mA] at $25^{\circ}C$ and $85^{\circ}C$, respectively.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.2
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• pp.93-101
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• 2002

We have proposed and fabricated two lateral type field emission diodes, poly-Si emitter by utilizing the local oxidation of silicon (LOCOS) and GaN emitter using metal organic chemical vapor deposition (MOCVD) process. The fabricated poly-Si diode exhibited excellent electrical characteristics such as a very low turn-on voltage of 2 V and a high emission current of $300{\;}\bu\textrm{A}/tip$ at the anode-to-cathode voltage of 25 V. These superior field emission characteristics was speculated as a result of strong surface modification inducing a quasi-negative electron affinity and the increase of emitting sites due to local sharp protrusions by an appropriate activation treatment. In respect, two kinds of procedures were proposed for the fabrication of the lateral type GaN emitter: a selective etching method with electron cyclotron resonance-reactive ion etching (ECR-RIE) or a simple selective growth by utilizing $Si_3N_4$ film as a masking layer. The fabricated device using the ECR-RIE exhibited electrical characteristics such as a turn-on voltage of 35 V for $7\bu\textrm{m}$ gap and an emission current of~580 nA/l0tips at anode-to-cathode voltage of 100 V. These new field emission characteristics of GaN tips are believed to be due to a low electron affinity as well as the shorter inter-electrode distance. Compared to lateral type GaN field emission diode using ECR-RIE, re-grown GaN emitters shows sharper shape tips and shorter inter-electrode distance.

• Journal of the Korea Institute of Military Science and Technology
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• v.1 no.1
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• pp.227-237
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• 1998

HgCdTe Is the most versatile material for the developing infrared devices. Not like III-V compound semiconductors or silicon-based photo-detecting materials, HgCdTe has unique characteristics such as adjustable bandgap, very high electron mobility, and large difference between electron and hole mobilities. Many research groups have been interested in this material since early 70's, but mainly due to its thermodynamic difficulties for preparing materials, no single growth technique is appreciated as a standard growth technique in this research field. Solid state recrystallization(SSR), travelling heater method(THM), and Bridgman growth are major techniques used to grow bulk HgCdTe material. Materials with high quality and purity can be grown using these bulk growth techniques, however, due to the large separation between solidus and liquidus line on the phase diagram, it is very difficult to grow large materials with minimun defects. Various epitaxial growth techniques were adopted to get large area HgCdTe and among them liquid phase epitaxy(LPE), metal organic chemical vapor deposition(MOCVD), and molecular beam epitaxy(MBE) are most frequently used techniques. There are also various types of photo-detectors utilizing HgCdTe materials, and photovoltaic and photoconductive devices are most interested types of detectors up to these days. For the larger may detectors, photovoltaic devices have some advantages over power-requiring photoconductive devices. In this paper we reported the main results on the HgCdTe growing and characterization including LPE and MOCVD, device fabrication and its characteristics such as single element and linear array($8{\times}1$ PC, $128{\times}1$ PV and 4120{\times}1$ PC). Also we included the results of the dewar manufacturing, assembling, and optical and environmental test of the detectors.