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공침법을 이용한 Lu<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup> 나노 형광체 합성과 광학적 특성 분석
강태욱,강현우,김종수,김광철,Kang, Taewook,Kang, Hyeonwoo,Kim, Jongsu,Kim, Gwangchul 한국반도체디스플레이기술학회 2019 반도체디스플레이기술학회지 Vol.18 No.4
LuAG:Ce(Lu3Al5O12:Ce3+) nano phosphor were synthesized by applying the coprecipitation method. It is used to increase the color rendering of phosphor ceramic plate for high power LEDs and laser lighting. Internal quantum efficiency and absorption of LuAG:Ce nano phosphor are 51.5 % and 64.4 %, respectively, which is higher than the previously studied nano phosphors. The maximum absorption wavelength of this phosphor is 450 nm blue light, and the emission wavelength is 510 nm. The emission wavelength shifted to longer wavelength when the concentration of Ce increased in the heat treatment of the reducing atmosphere. Thermal quenching of LuAG nano phosphor was 70 % at 200 ℃, it was explained by their significant quenching of all raman scattering modes, implying the restriction of electron-phonon couplings caused by their defects.
백색 레이저 조명용 Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup>,Pr<sup>3+</sup> 단결정 특성
강태욱,임석규,김종수,이봉,Kang, Taewook,Lim, Seokgyu,Kim, Jongsu,Lee, Bong 한국반도체디스플레이기술학회 2018 반도체디스플레이기술학회지 Vol.17 No.4
$Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was prepared by floating zone method. single crystal was confirmed to have a Ia-3d (230) space group of cubic structure and showed regular morphology. The optical properties, single crystal exhibited a emission band from green, yellow wide wavelength and 610nm, 640nm red wavelength vicinity. The luminance maintenance rate was decreased by phonon with increasing temperature, but high luminance is maintained more than powder phosphor. In addition, $Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was applied to a high power blue laser diode, we implemented high power white laser lightings. and it was confirmed that thermal properties over time, due to the effective heat transfer of complete crystal structure. We confirmed that excellent radiant heat properties than powder phosphor was applied to a high power white laser diode.
CaYAlO<sub>4</sub>:Tb<sup>3+</sup>/Eu<sup>3+</sup>/Ce<sup>3+</sup>형광체의 광학적 특성 분석
강태욱,류종호,김종수,김광철,Kang, Taewook,Ryu, Jongho,Kim, Jongsu,Kim, Gwang Chul 한국반도체디스플레이기술학회 2017 반도체디스플레이기술학회지 Vol.16 No.4
$Tb^{3+}$ or $Eu^{3+}$ or $Ce^{3+}$-doped $CaYAlO_4$ phosphor were synthesized by solid-state method. $CaYAlO_4:Tb^{3+}$ is shown that the $Tb^{3+}$-doping concentration has a significant effect on the $^5D_4/^5D_3{\rightarrow}7F_J$ (J=6,...,0) emission intensity of $Tb^{3+}$. The $CaYAlO_4:Tb^{3+}$ phosphors show tunable photoluminescence from blue to yellow with the change of doping concentration of $Tb^{3+}$ ions. The $CaYAlO_4:Eu^{3+}$ phosphors exhibit a red-orange emission of $Eu^{3+}$ corresponding to $^5D_0$, $_{1,2}{\rightarrow}^7F_J$ (J=4,...,0) transitions. The $CaYAlO_4:Ce^{3+}$ phosphors show a blue emission due to $Ce^{3+}$ ions transitions from the 5d excited state to the $^2F_{5/2}$ and $^2F_{7/2}$ ground states. The decay time of $CaYAlO_4:Tb^{3+}$ phosphors decrease from 1.33 ms to 0.97 ms as $Tb^{3+}$ concentration increases from 0.1 mol% to 7 mol%. The decay time of $CaYAlO_4:Eu^{3+}$ phosphors increase from 0.94 ms to 1.17 ms as $Eu^{3+}$ concentration increases from 1 mol% to 9 mol%.
강태욱,김효준,정용석,김종수,Kang, Taewook,Kim, Hyojun,Jeong, Yongseok,Kim, Jongsu 한국재료학회 2020 한국재료학회지 Vol.30 No.8
A transparent quantum dot (QD)-based light-emitting diode (LED) with silver nanowire (Ag NW) and indium-tin oxide (ITO) hybrid electrode is demonstrated. The device consists of an Ag NW-ITO hybrid cathode (-), zinc oxide, poly (9-vinylcarbazole) (PVK), CdSe/CdZnS QD, tungsten trioxide, and ITO anode (+). The device shows pure green-color emission peaking at 548 nm, with a narrow spectral half width of 43 nm. Devices with hybrid cathodes show better performances, including higher luminance with higher current density, and lower threshold voltage of 5 V, compared with the reference device with a pure Ag NW cathode. It is worth noting that our transparent device with hybrid cathode exhibits a lifetime 9,300 seconds longer than that of a device with Ag NW cathode. This is the reason that the ITO overlayer can protect against oxidization of Ag NW, and the Ag NW underlayer can reduce the junction resistance and spread the current efficiently. The hybrid cathode for our transparent QD LED can applicable to other quantum structure-based optical devices.
강태욱,임석규,김종수,정용석,Kang, Taewook,Lim, Seokgyu,Kim, Jongsu,Jeong, Yongseok 한국재료학회 2019 한국재료학회지 Vol.29 No.2
We prepared $Y_3Al_5O_{12};Ce^{3+},Pr3^{+}$ transparent ceramic phosphor using a solid state reaction method. By XRD pattern analysis and SEM measurement, our phosphors reveal an Ia-3d(230) space group of cubic structure, and the transparent ceramic phosphor has a polycrystal state with some internal cracks and pores. In the Raman scattering measurement with an increasing temperature, lattice vibrations of the transparent ceramic phosphor decrease due to its more perfect crystal structure and symmetry. Thus, low phonon generation is possible at high temperature. Optical properties of the transparent ceramic phosphor have broader excitation spectra due to a large internal reflection. There is a wide emission band from the green to yellow region, and the red color emission between 610 nm and 640 nm is also observed. The red-yellow phosphor optical characteristics enable a high Color Rendering Index (CRI) in combination with blue emitting LED or LD. Due to its good thermal properties of low phonon generation at high temperature and a wide emission range for high CRI characteristics, the transparent ceramic phosphor is shown to be a good candidate for high power solid state white lighting.
요추 척추관 협착증 환자의 양방향 경피적 내시경을 이용한 척추 수술
강태욱(Taewook Kang),이순혁(Soon Hyuck Lee),박시영(Si Young Park) 대한정형외과학회 2019 대한정형외과학회지 Vol.54 No.3
요추 척추관 협착증에서 다양한 방법으로 감압술을 시행하고 있으며, 최근 들어 고식적인 척추관 감압술의 여러 합병증을 최소화하기 위하여 최소 침습적 척추 수술이 시행되고 있다. 단방향 내시경을 이용한 감압술은 구조적으로 한계가 있어 그 사용이 제한적이기 때문에 양방향 내시경을 이용한 감압술을 시행하고 있다. 요추 척추관 협착증에서 양방향 내시경을 이용한 감압술은 안전하게 충분한 감압술을 시행할 수 있는 만족스러운 수술법이다. Lumbar decompressive surgery is a standard surgery for lumbar spinal stenosis. Many surgical techniques have been introduced, ranging from open surgery to percutaneous procedures. Minimally invasive techniques are preferred because of the less postoperative pain and shorter hospital stay. Uniportal percutaneous endoscopic decompression has technical difficulties due to the narrow field. Biportal percutaneous endoscopic decompression is a satisfactory technique that can compensate for the shortcomings and provide sufficient decompression.