• 한국초전도ㆍ저온공학회논문지
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• 제21권3호
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• pp.6-12
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• 2019

Extended Drude model has been used to obtain information of correlations from measured optical spectra of strongly correlated electron systems. The optical self-energy can be defined by the extended Drude model formalism. One can extract the optical self-energy and the electron-boson spectral density function from measured reflectance spectra using a well-developed usual process, which is consistent with several steps including the extended Drude model and generalized Allen's formulas. Here we used a reverse process of the usual process to investigate the extended Drude analysis when an additional low-energy interband transition is included. We considered two typical electron-boson spectral density model functions for two different (normal and d-wave superconducting) material states. Our results show that the low-energy interband transition might give significant effects on the electron-boson spectral density function obtained using the usual process. However, we expect that the low-energy interband transition can be removed from measured spectra in a proper way if the transition is well-defined or well-known.

• Advances in nano research
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• 제3권1호
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• pp.13-27
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• 2015

Size dependent emission properties and the interband optical transition energies in group-III nitride based quantum dots are investigated taking into account the geometrical confinement. Exciton binding energy and the optical transition energy in $Ga_{0.9}In_{0.1}N$/GaN and $Al_{0.395}In_{0.605}N$/AlN quantum dots are studied. The largest intersubband transition energies of electron and heavy hole with the consideration of geometrical confinement are brought out. The interband optical transition energies in the quantum dots are studied. The exciton oscillator strength as a function of dot radius in the quantum dots is computed. The interband optical absorption coefficients in GaInN/GaN and AlInN/AlN quantum dots, for the constant radius, are investigated. The result shows that the largest intersubband energy of 41% (10%) enhancement has been observed when the size of the dot radius is reduced from $50{\AA}$ to $25{\AA}$ of $Ga_{0.9}In_{0.1}N$/GaN ($Al_{0.395}In_{0.605}N$/AlN) quantum dot.

• Applied Science and Convergence Technology
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• 제24권5호
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• pp.167-171
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• 2015

Quantum-confined nanostructures open up additional perspectives in engineering materials with different electronic and optical properties. We have fabricated unique cation-exchanged CdS and CdS/CdSe quantum dots and measured their first four exciton transitions. We demonstrate that the relationship between electronic transitions and charge-carrier distributions is generalized for a broad range of core-shell nanostructures. These nanostructures can be used to further improve the performance in the fields of bio-imaging, light-emitting devices, photovoltaics, and quantum computing.

• 한국자기학회지
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• 제4권2호
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• pp.154-159
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• 1994

비정질 RE-Co(RE=Ce, Nd, Pr, Gd, Tb, Er, Ho) 합금막의 자기광학 스펙트럼(${\lambda}=250~700nm$)을 Y-Co의 그것과 비교하여 RE 부격자에 의한 자기광학효과를 추정하였다. RE에 의한 자기광학효과는 단파장 영역에서 크게 기여하는 것으로 나타났으며, Ce, Pr, Nd 및 Gd은 Co의 자기광학효과에 더해지는 방향으로 일어나고, Tb, Ho 및 Er은 Co와 반대방향으로 일어난다. 자기광학 천이 모델에 의하면, Pr과 Nd은 $4f{\uparrow}->5d{\uparrow}$, Ce과 Gd은 d->p, Tb은 $4f{\downarrow}->5d{\downarrow}$ 또는 $5d{\downarrow}->4f{\downarrow}$ 그리고 Ho과 Er은 $4f{\downarrow}->5d{\downarrow}$ 밴드간 천이에 의한 것으로 각각의 자기광학횬과를 설명할 수 있다.

• 한국표면공학회지
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• 제29권6호
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• pp.788-796
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• 1996

$TiO_2$ films prepared by RF magnetron sputtering, electron beam evaporation, ion assisted deposition (IAD) and sol-gel method are prepared on c-Si substrate and vitreous silica substrate respectively. From the transmission spectra of $TiO_2$ films on vitreous silica substrate in the spectral region from 190 nm to 900 nm, k($\lambda$) of $TiO_2$ is obtained. Using k($\lambda$) in the interband transition region the coefficients of the quantum mechanical dispersion relation of an amorphous $TiO_2$ and hence n($\lambda$) including the optically opaque region of above fundamental transition energy are obtained. The spectroscopic ellipsometry spectra of $TiO_2$ films in the spectral region of 1.5-5.0eV are model analyzed to get the film packing density variation versus i) substrate material, ii) film thickness and iii) film growth technique. The complex refractive index change of these $TiO_2$ films versus water condensation is also studied. Film micro-structures by SE modelling results are compared with those by atomic force microscopy images and X-ray diffraction data.

• Applied Science and Convergence Technology
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• 제24권5호
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• pp.156-161
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• 2015

Application of magnetic fields is important to characterize the carrier dynamics in semiconductor quantum structures. We performed photoluminescence (PL) measurements from an InGaP-AlInGaP single quantum well under pulsed magnetic fields to 50 T. The zero field interband PL transition energy matches well with the self-consistent Poisson-$Schr{\ddot{o}}dinger$ equation. We attempted to analyze the dimensionality of the quantum well by using the diamagnetic shift of the magnetoexciton. The real quantum well has finite thickness that causes the quasi-two-dimensional behavior of the exciton diamagnetic shift. The PL intensity diminishes with increasing magnetic field because of the exciton motion in the presence of magnetic field.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.332.1-332.1
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• 2016

Application of magnetic fields is important to characterize the carrier dynamics in semiconductor quantum structures. We performed photoluminescence (PL) measurements from an InGaP-AlInGaP single quantum well under pulsed magnetic fields to 50 T. The zero field interband PL transition energy matches well with the self-consistent Poisson-Schr?dinger equation. We attempted to analyze the dimensionality of the quantum well by using the diamagnetic shift of the magnetoexciton. The real quantum well has finite thickness that causes the quasi-two-dimensional behavior of the exciton diamagnetic shift. The PL intensity diminishes with increasing magnetic field because of the exciton motion in the presence of magnetic field.