• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.201-208
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• 2006

Optical characteristics of InGaAs quantum dot (QD) laser structures with an Al native oxide (AlOx) layer as a current-blocking layer were studied by means of photoluminescence (PL), PL excitation, and spatially-resolved micro-PL techniques. The InGaAs QD samples were first grown by molecular-beam epitaxy (MBE), and then prepared by wet oxidation and thermal annealing techniques. For the InGaAs QD structures treated by the wet oxidation and thermal annealing processes, a broad PL emission due to the intermixing effect of the AlOx layer was observed at PL emission energy higher than that of the non-intermixed region. We observed a dominant InGaAs QD emission at about 1.1 eV in the non-oxide AlAs region, while InGaAs QD-related emissions at about 1.16 eV and $1.18{\sim}1.20eV$ were observed for the AlOx and the SiNx regions, respectively. We conclude that the intermixing effect of the InGaAs QD region under an AlOx layer is stronger than that of the InGaAs QD region under a non-oxided AlAs layer.

• Journal of Powder Materials
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• v.19 no.5
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• pp.362-366
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• 2012

We report the effect of the chain length of carboxylic acid on the photoluminescence(PL) of $CuInS_2$/ZnS nanocrystals. $CuInS_2$/ZnS nanocrystals with emission wavelength ranging from 566 nm through 583 nm were synthesized with zinc acetate and carboxylic acids with various chain length. In this study, $CuInS_2$/ZnS nanocrystals prepared using long chain carboxylic acid showed more improved PL intensity. The origin of strong photoluminescence of the nanocrystals prepared with zinc acetate and long chain carboxylic acid was ascribed to improved size distribution due to strong reactivity between long chain carboxylic acid and zinc acetate.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.900-904
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• 2011

We have synthesized core-shell structured nanocrystals based on chalcopyrite-type $Cu_{0.2}InS_2$. The photoluminescence of the nanocrystals shows a significant blueshift in the emission wavelength by shell capping with ZnS layers. This shift can be explained with the compressive stress to core nanocrystals applied by the formation of a ZnS shell layer with a large lattice mismatch with the core. In this study, the emission wavelength could be tuned by changing the composition of the shell layers. Nanocrystals with emission wavelength ranging from 575 nm through 630 nm were synthesized by varying the portion of cadmium compared with zinc in the shell layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.387-387
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• 2007

기능성 나노소자를 구현할 수 있는 나노 소재로 0차원 구조의 양자점(quantum dot)과 1차원 구조의 양자선 및 나노선(nanorod)이 제안되고 있다. 나노선의 경우 나노스케일의 dimension, 앙자 제한 효과, 탁월한 결정성, self-assembly, internal stress등 기존의 벌크형 소재에서 발견할 수 없는 새로운 기능성이 나타나고 있어서 바이오, 에너지, 구조, 전자, 센서 등의 분야에서 활용되고 있다. 현재 국내외적으로 널리 연구되고 있는 나노선으로는 Si 및 Ge, $SnO_2$, SiC, ZnO 등이 있으며 특히, ZnO는 우수한 물리적 전기적 특성과 함께 나노선으로의 합성이 비교적 쉬워 주목받고 있는 재료이다. ZnO의 합성방법으로는 thermal CVD, MOCVD, PLD, wet-chemistry 등 다양한 방법이 사용되고 있다. 특히 MOCVD 법은 수직 정렬된 ZnO 나노막대를 합성하기가 매우 용이하다. 본 실험에서는 자체개발된 MOCVD 장비를 이용한 일차원 ZnO 나노선을 성장하였다. 이러한 ZnO 나노선의 성장은 사파이어 기판과 실리콘 기판 위에서 이루어졌으며 기판의 종류와 격자상수 불일도에 따른 상이한 성장과정을 온도에 따른 나노선 성장에서 관찰할 수 있었다. 사파이어 기판의 경우, 240도의 온도에서는 박막형상을 지닌 ZnO가 온도가 320도 이상으로 상승하면서 나노선으로 변함을 보였고, 실리콘 기판의 경우 380도 이상에서 기울기률 가진 나노선을 관찰하였으며, 420도에서는 나노선을 관찰 할 수 없었다. 또한 PL 장비를 이용한 PL 강도와 성장과정을 연관하여 생각하였을 때, 나노선의 기물기가 PL 강도비과 연관성을 가진다는 것을 측정을 통해 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Current Optics and Photonics
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• v.3 no.6
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• pp.590-596
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• 2019

To improve the color gamut of a liquid-crystal display (LCD), we propose a bandpass filter that is added to the backlight unit to optimize the backlight spectrum. The bandpass filter can only transmit red, green and blue light in the visible range, while reflecting the unwanted light. We study the optical properties of the bandpass filter using the transfer-matrix method, and the effect of the bandpass filter on the color gamuts of LCDs is also investigated. When a bandpass filter based on a 5-layer configuration comprising low and high refractive indices ((HL)²H) is used in phosphor-converted white-light-emitting diode (pc-WLED), K₂SiF₆:Mn⁴⁺ (KSF-LED), and quantum-dot (QD) backlights, the color gamuts of the LCDs improve from 72% to 95.3% of NTSC, from 92% to 106.7% of NTSC, and from 104.3% to 112.2% of NTSC respectively. When the incident angle of light increases to 30°, the color gamuts of LCDs with pc-WLED and KSF-LED backlights decrease by 2.9% and 1% respectively. For the QD backlight, the color gamut almost does not change. When the (HL)²H structure is coated on the diffusion film, the color gamut can be improved to 92.6% of NTSC (pc-WLED), 105.6% of NTSC (KSF-LED), and 111.9% of NTSC (QD). The diffusion film has no obvious effect on the color gamut. The results have an important potential application in wide-color-gamut LCDs.