• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.493-498
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• 1998

ZnS doped borosilicate glass for nonlinear optical application was prepared by melting and precipitation process. The optical band gap of the precipitated ZnS particles ranged from 3.83 to 3.96 eV compared with the bulk ZnS energy gap of 3.53 eV. This result was interpreted in terms of a quantum confinement effect due to small crystal size. ZnS partilcle size estimated by effective mass approximation ranged from about 39 to 83 $\AA$ It increased wtih the increase of heat tratment time and temperature.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.86.1-86.1
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• 2010

Cu2ZnSnSe4는 CIS 태양전지의 In 대체 물질계로 주목을 받고 있는 저가형 태양전지 재료로 장차 차세대 태양전지 재료로 응용이 기대되고 있다. 그러나 에너지 밴드갭이 0.9~1.1eV로 다소 낮아 태양전지 광흡수층 재료로 사용하기 위해서는 wide band gab화 처리가 필요하다. 본 연구에서는 CZTSe에 S를 첨가하여 에너지 밴드갭을 확장하고자 하며, S의 첨가가 CZTSe 박막의 특성에 미치는 영향에 대하여 조사하였다. 실험의 편의성을 도모하고자 펄스레이저 법을 사용하여 증착하였다. 박막 조성 제어에는 Cu, Zn, Sn, Se, S 분말을 볼밀로 분쇄, 혼합하여 균질 혼합상 프리커서를 제조하고 이를 Cold Isostatic Press(CIP) 성형하여 Source target을 사용하였다. Pulsed YAG-Laser를 사용하여 soda lime glass상에 증착하고 조성, 구조, 조직을 관찰하고 에너지 밴드갭, 광흡수계수, 면저항, 전하밀도 등 특성을 조사하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.85-86
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• 2006

Single crystal $AgGaSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_2$ source at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $AgGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=19501 eV-(879{\times}10^{-4} eV/K)T^2/(T+250 K)$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.119-122
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• 2003

We report a dramatic increase in the photo-stability of a blue-emitting polymer, poly(9,9-dioctylfluorene), achieved by the addition of gold nanoparticles to the polymer. The optical absorption band of gold nanoparticles is tuned to resonate the triplet exciton-ground state band gap energy of the polymer. The photo-oxidation rate of poly(9,9-dioctylfluorene) was drastically reduced by doping the polymer with a very small amount ($10^{-6}-10^{-5}$ volume fraction) of gold nanoparticles. The gold nanoparticles used herein act as the quenching agent of the triplet states and can be directly applied to various blue light emitting polymer thin film ( < 100 nm ) devices.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.431-434
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• 2014

Wind turbine industry is the most developing field among other renewable energy industry. As expanding wind farms, noise is the big problem to solve. This study is about wind turbine noise measuring method based on IEC 61400-11. Sound pressure levels, 1/3-octave band levels, and low frequency sound pressure levels of a 3 MW wind turbine were measured and analyzed.

• Journal of Energy Engineering
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• v.22 no.1
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• pp.58-81
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• 2013

Recently, the technological progress in manufacturing power devices based on wide bandgap materials, for example, silicon carbide(SiC) or gallium nitride(GaN), has resulted in a significant improvement of the operating-voltage range and switching speed and/or specific on resistance compared with silicon power devices. This paper will give an overview of the status on The Next generation Power Devices such as SiC/GaN with a focus on commercialization and research.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.314-318
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• 1989

Thin films of undoped and Ga-doped zinc oxide have been prepared by rf sputtering. The films deposited on substrates, which have a columnar structure with the c-axis perpendicular to the substrate surface, consist of very small crystal grains (500-1000 ${\AA}$). Considering doping effects, the electrical resistivity of Ga-doped films decreased by an order of $10^3$ compared to undoped films and the optical transmission was above 80% in the visible range and the optical band gap widened as the Ga content increased.

• Advances in nano research
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• v.3 no.1
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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.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.477-477
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• 2012

The effects of argon neutral beam (NB) energy on the amorphous carbon (a-C) films were investigated, while the a-C films were deposited by neutral particle beam assisted sputtering (NBAS) system. The deposition characteristics of these films were studied as a function of NB energy (or reflector bias voltage). The film structures were investigated by Raman spectroscopy. The hardness was measured by nano-indentation tests and the optical band gap was measured by UV-visible spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1235-1241
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• 2012

Aluminium (Al)-doped zinc oxide (AZO) thin films with different Al concentrations were prepared by the solgel spin-coating method. Optical parameters such as the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity were studied in order to investigate the effects of the Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at infinite wavelength of the AZO thin films were found to be affected by Al incorporation. The optical conductivity of the AZO thin films also increases with increasing photon energy.