• Particle and aerosol research
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• v.6 no.2
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• pp.51-59
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• 2010

ZnO quantum dots embedded in a silica matrix without agglomeration were synthesized from $TEOS:Zn(NO_3)_2$ solutions in one-step process by aerosol-gel method. It was successfully demonstrated that the size of ZnO Q-dots could be controlled from 2 to 7 mm verified by a high resolution transmission electron microscope observation. The line scanning energy dispersive X-ray spectroscopy(EDS) revealed that the Q-dots existed preferentially inside SiO2 sphere when Zn/Si < 0.5. However, the Q-dots distributed homogeneously all over the sphere when Zn/Si > 1.0. Blue-shifted UV/Vis absorption peak observation confirmed the quantum size effect on the optical properties. The photoluminescence(PL) emission peaks of the powders at room temperature were consistent with previous reports in the following aspects: 1) PL characteristics are dominated by two peaks of deep-level defect-related emissions at 2.4 - 2.8 eV, 2) the first defect-related peak at 2.4 eV was blue shifted due to the quantum size effect with decreasing the concentration of $Zn(NO_3)_2$(decreasing the size of ZnO q dots). More interestingly, the existence of surface-exposed ZnO q dots affects greatly the second defect PL peak at 2.8 eV.

• Vacuum Magazine
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• v.4 no.4
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• pp.14-17
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• 2017

Recently, quantum-dots light emitting diodes (QLEDs) are considered as a next-generation display due to the superior luminescence behaviors, photo stability and narrow spectral emission bandwidth. Moreover, the emission color of QLEDs can be easily controlled by changing the dimension of quantum dots (QDs). A flexible display based on QLEDs can be achieved using low-cost solution process, such as a printing technology. Therefore, QLEDs are expected as a next generation display. In this document, recent progresses in QDs technology will be introduced.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.571-574
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• 2012

In present study, CdSe quantum dots (QDs) were prepared with a novel but simple, effective and exercisable method. Nine different types of carbohydrate molecules were used to modify CdSe QDs. D-mannose (Man)-coated quantum dots were prepared for labeling human hepatoma (HepG2) cells, because of the high expression of mannose receptor (MR) on HepG2 cells. The uptake characteristics of CdSe QDs-Man were investigated in HepG2 cells. The absorption rate result of MTT assay in 48 h suggested the extremely low cytotoxicity of CdSe QDs-Man. The presence of quantum dots was confirmed with fluorescence microscopy. These results were encouraging regarding the application of QDs molecules for early detection of HepG2 cells.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.257-261
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• 2001

InAs/GaAs quantum dots between InGaAs/GaAs superlattices were grown by MBE. The quantum dots size is shown to be very uniform by measuring photoluminescence spectra of quantum dots. Single photon structures based on self-consistent calculation were grown and single photon devices were fabricated by e-beam lithography. The electrical hystereses of I-V curves for single Photon devices would result from single electron-hole recombination, where the resonant-tunneling voltages of electron and hole are different.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.588-590
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• 2008

Yellow-emitting $Y_3Al_5O_{12}$:Ce nanocrystalline phosphor and orange-emitting CdS:Mn/ZnS core/shell quantum dots were prepared by a modified polyol and a reverse micelle chemistry, respectively. To compensate a poor color rendering index of YAG:Ce nanocrystalline phosphor due to the lack of red spectral component, CdS:Mn/ZnS quantum dots were blended into YAG:Ce. Based on spectral evolutions in the blended systems, hybrid white light emitting diodes are fabricated and characterized.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.527-531
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• 2005

Fully coherent self-assembled InAs quantum dots(QDs) grown on Si (100) substrates by atmospheric pressure metalorganic chemical vapor deposition(APMOCVD) were grown and the effect of growth conditions such as growth rate and growth time on quantum dots' morphology such as densities and sizes was investigated. InAs QDs of 30 - 80 nm in diameters with densities in the range of (0.6 - 1.7) x $10^{10}\;cm^{-2}$ were achieved on Si substrates and InAs layer was changed from 2 dimensional growth to 3 dimensional one at a nominal thickness less than 0.48 ML. This is attributed to the higher ambient pressure of APMOCVD suppressing of In segregation from the 2 dimensional InAs layer. This In segregation looked to disturb the dot formation especially when the growth rate was low so that the dots became less dense and bigger as the growth rate was lower.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.195-197
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• 2002

CdTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. Photoluminescence(PL) spectra of the synthesized CdTe QDs revealed the intensity of PL peaks was stronger as the condensation time was longer. This result was thought because annealing effect by thermal energy transferred during condensation eliminated defects which act as traps and recombination centers in CdTe particle. PL intensity has stron dependence of Te precursor concentration. It confirmed the ratio of Te ion to Cd ion added during synthesis affected the particle size and size distribution of the CdTe QDs. Finally, the synthesized CdTe QDs were identified to be cubic structured CdTe quantum dots by X-ray diffraction(XRD).

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.94-98
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• 2020

The core/shell of nanowires (NWs) with Cu-doped CdSe quantum dots were fabricated as an electron transport layer (ETL) for perovskite solar cells, based on ZnO/TiO2 arrays. We presented CdSe with Cu2+ dopants that were synthesized by a colloidal process. An improvement of the recombination barrier, due to shell supplementation with Cu-doped CdSe quantum dots. The enhanced cell steady state was attributable to TiO2 with Cu-doped CdSe QD supplementation. The mechanism of the recombination and electron transport in the perovskite solar cells becoming the basis of ZnO/TiO2 arrays was investigated to represent the merit of core/shell as an electron transport layer in effective devices.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.245-249
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• 2015

Vertically coupled low density InGaAs quantum dots (QDs) buried in GaAs matrix were grown with migration enhanced molecular beam epitaxy method as a candidate for quantum information processing devices. We performed excitation power-dependent photoluminescence measurements at cryogenic temperature to analyze the effects of vertical coupling according to the variation in thickness of spacer layer. The more intense coupling effects were observed with the thinner spacer layer, which modified emission properties of QDs significantly. The low surface density of QDs was observed by atomic force microscopy, and scanning transmission electron microscopy verified the successful vertical coupling between low density QDs.

• Journal of the Optical Society of Korea
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• v.15 no.2
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• pp.124-127
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• 2011

Quantum dots were designed within a GRIN-SCH(Graded index - Separate confinement Heterostructure) heterostructure to create a high power InAlAs/AlGaAs laser diode. 808 nm light emission was with a quantum dot composition of In0.665Al0.335As and wetting layer composition of Al0.2Ga0.8As by LASTIP simulation software. Typical characteristics of GRIN structures such as high confinement ratios and Gaussian beam profiles were shown to still apply when quantum dots are used as the active media. With a dot density of 1.0x1011 dots/cm2, two quantum dot layers were found to be good enough for low threshold, high-power laser applications.