• Current Optics and Photonics
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• 제3권2호
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• pp.143-149
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• 2019

Shape ellipticity dependence of the exciton fine energy levels in CdTe and CdSe nanocrystal quantum dots were compared theoretically by considering the crystal structure and the Coulomb interaction of an electron and a hole. While quantum dot ellipticity changes from an oblate to prolate quantum dot via spherical shape, both the fine energy levels and the dipole moment in wurtzite structure of a CdSe quantum dot change linearly for ellipticity. In contrast, CdTe quantum dots were found to show a level crossing between the bright and dark exciton states with a significant change of the dipole moment due to the cubic structure. Shape ellipticity dependence of the optical nonlinearities in CdTe and CdSe nanocrystal quantum dots was also calculated by using semiconductor Bloch equations. For a spherical shape quantum dot, only $1^L$ dominates the optical nonlinearities in a CdSe quantum dot, but both $1^U$ and $0^U$ contribute in a CdTe quantum dot. As excitation pulse area becomes strong (${\sim}{\pi}$), the optical nonlinearities of both CdSe and CdTe quantum dots are mainly governed by absorption saturation. However, in the case of a prolate CdTe quantum dot, the real part of the nonlinear refractive index becomes relatively significant.

• 한국분말재료학회지
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• 제19권6호
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• pp.451-457
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• 2012

Nowadays, research and development on quantum dot have been intensively and comprehensively pursued worldwide in proportion to concurrent breakthrough in the field of nanotechnology. At present, quantum dot technology forms the main interdisciplinary basis of energy, biological and photoelectric devices. More specifically, quantum dot semiconductor is quite noteworthy for its sub-micro size and possibility of photonic frequency modulation capability by controlling its size, which has not been possible with conventionally fabricated bulk or thin film devices. This could lead to realization of novel high performance devices. To further understand related background knowledge of semiconductor quantum dot at somewhat extensive level, a review paper is presently drafted to introduce basics of (semiconductor) quantum dot, its properties, applications, and present and future market trend and prospect.

• 전자통신동향분석
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• 제35권2호
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• pp.79-88
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• 2020

Quantum computing is regarded as one of the revolutionary computing technologies, and has attracted considerable attention in various fields, such as finance, chemistry, and medicine. One of the promising candidates to realize fault tolerant quantum computing is quantum dot qubits, due to their expectation of high scalability. In this study, we briefly introduce the international tendencies for quantum dot quantum computing. First, the current status of quantum dot gate operations is summarized. In most systems, over 99% of single qubit gate operation is realized, and controlled-not and controlled-phase gates as 2-qubit entangling gates are demonstrated in quantum dots. Second, several approaches to expand the number of qubits are introduced, such as 1D and 2D arrays and long-range interaction. Finally, the current quantum dot systems are evaluated for conducting quantum computing in terms of their number of qubits and gate accuracies. Quantum dot quantum computing is expected to implement scalable quantum computing. In the noisy intermediate-scale quantum era, quantum computing will expand its applications, enabling upcoming questions such as a fault-tolerant quantum computing architecture and error correction scheme to be addressed.

• 한국결정성장학회지
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• 제30권2호
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• pp.78-81
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• 2020

양자점은 산소와 수분에 취약하기 때문에 수분과 산소를 막아줄 수 있는 베리어 특성을 가진 제품을 이용하여 샌드위치 형식 양자점 층을 감싸는 형태로 제조하여 양자점의 광학적 신회성을 평가하였다. 다른 보호막이 없는 양자점 레진으로만 이루어진 필름, 양자점 필름과 PET를 합지한 필름 및 베리어 필름을 합지한 양자점 필름, 3가지를 이용하여 온도 60℃, 습도 90 %인 고온고습 조건에서 650시간 동안 변화를 평가를 진행하였다. 베리어 필름과 합지한 양자점 필름 제품은 휘도와 CIE x 및 CIE y 값이 유지되는 반면 PET와 합지한 양자점 필름 제품은 휘도 8 %, CIE x 2 % 및 CIE y 8 %가 낮아졌다. 또한 수분과 산소에 그대로 노출되었던 양자점 필름 제품은 측정 전부터 산화되어 낮게 측정되었으며 최종적으로 휘도 12 %, CIE x 9 % 및 CIE y 14 %가 낮게 측정되었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.21-21
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• 2004

• 진공이야기
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• 제4권4호
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• pp.4-13
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• 2017

Quantum structures containing nanoparticles have attracted much attention because of their promising potential applications in electronic and optoelectronic devices operating at lower currents and higher temperatures. The quantum dot is a particle of matter so small that the addition or removal of an electron changes its properties in some useful way. The Quantum dots typically have dimensions measured in nanometers, where one nanometer is 10-9 meter or a millionth of a millimeter. The emission and absorption spectra corresponding to the energy band gap of the quantum dot is governed by quantum confinement principles in an infinite square well potential. The energy band gap increases with a decrease in size of the quantum dot. In this review paper, we will discuss the quantum dot and their application.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3787-3789
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• 2013

In this study, the silicone thermal curing degree of the silicone-encapsulated quantum dot light emission diode was measured using the various types of chemical ligands around quantum dot. It was confirmed that the trioctyl phosphin oxide (TOPO) ligand around the quantum dot was responsible for dispersion of the quantum dot in silicone encapsulant and decline of the thermal curing degree of the silicone encapsulant. Also, it was confirmed that the thermal curing degree of silicone encapsulants containing the steric acid (SA) and the dodecanoic acid (DA) ligands were higher than the one of TOPO ligand.

• Journal of the Optical Society of Korea
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• 제19권3호
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• pp.272-276
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• 2015

The PbS quantum dot is an emerging photovoltaic material, which may provide high efficiency breakthroughs. The most crucial element for the high efficiency solar cells's development is to understand charge transport characteristics of PbS quantum dot solids, which are also important in planning strategic research. We have investigated charge transport characteristics of PbS quantum dot solids thin films using space charge limited conduction analysis and assessed thickness dependent photovoltaic performances. The extracted carrier drift mobility was $low-10^{-2}cm^2/Vs$ with the estimated diffusion length about 50 nm. These and recently reported values were compared with those from a commercial photovoltaic material, and we present an essential element in further development of PbS quantum dot solids materials.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.154-157
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• 2016

The energy dispersion and magnetization of a modified magnetic dot are investigated numerically. The effects of additional electrostatic potential, magnetic field non-uniformity, and Zeeman spin splitting are studied. The modified magnetic quantum dot is a magnetically formed quantum structure that has different magnetic fields inside and outside of the dot. The additional electrostatic potential prohibits the ground-state angular momentum transition in the energy dispersion as a function of the magnetic field inside the dot, and provides oscillation of the magnetization as a function of the chemical potential energy. The magnetic field non-uniformity broadens the shape of the magnetization. The Zeeman spin splitting produces additional peaks on the magnetization.

• Journal of the Optical Society of Korea
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• 제15권2호
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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.