Optical Properties of ZnO Powder Prepared by Using a Proteic Sol-gel Process

권봉준,우현주,박지연,장기완,임승혁,조용훈 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.5

We have studied the optical properties of ZnO powder synthesized by using a proteic sol-gel process with coconut water as the precursor. The energy dispersive X-ray spectrometer and X-ray diffraction results show high purity of the synthesized ZnO powder. From the low-temperature (12 K) and power-dependent PL spectra, the donor-bound exciton, the acceptor-bound exciton, the donor-to-acceptor pair (DAP), and the phonon-replica of the DAP transition have been observed at 3.38, 3.34, 3.26, and 3.19 eV, respectively. The free exciton emission (3.3 eV) is also observed at 300 K in the temperature-dependent PL spectra.

Optical Properties of CaSrSiO4:Eu2+ Phosphors Prepared by Using a Solid-state Reaction Method for White Light-emitting Diodes

권봉준,Sakthivel GANDHI,우현주,조경미,이호섭,장기완,신동수,정중현 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.3

We have studied the optical properties of CaSrSiO4:Eu2+ phosphors synthesized by using the conventional solid-state reaction method and the role of Eu3+ minority ions in those phosphors. The maximum photoluminescence integrated peak intensity was observed for the Ca1−xSr1−xSiO4:2xEu2+ (2x = 0.0050) phosphor. A red shift of 3 nm from 510 to 513 nm in the emission wavelength of the CaSrSiO4:Eu2+ phosphors was observed with increasing Eu concentration. Under an excitation of 244 nm, the Ca1−xSr1−xSiO4:2xEu2+ (2x = 0.0050) phosphor showed a broad emission band at about 515 nm due to the 4f65d1 ! 4f7 transition of the Eu2+ and small sharp peaks at about 594, 612, and 701 nm corresponding to the 5D0-7FJ transitions of Eu3+. The existence of Eu3+ minority ions in the phosphor resulted in a broader full width at half maximum in the emission of the phosphor at the excitation wavelength of 390 400 nm, even at low Eu concentration. The white light-emitting diodes (LEDs) were fabricated by using the CaSrSiO4:Eu2+ phosphors and 400-nm GaN-based LED chips and exhibited a high color rendering index of 95 and correlated color temperature of 5370 K. The broad emissions of the CaSrSiO4:Eu2+ phosphors combined with the GaN-based LED chips are suitable for the realization of white LEDs.

AlAs 습식산화와 열처리로 인한 InGaAs 양자점 레이저 구조의 Intermixing효과에 관한 공간 분해 광학적 특성

황준석,권봉준,곽호상,최재원,조용훈,조남기,전헌수,조운조,송진동,최원준,이정일,Hwang J.S.,Kwon B.J.,Kwack H.S.,Choi J.W.,Choi Y.H.,Cho N.K.,Cheon H.S.,Cho W.C.,Song J.D.,Choi W.J.,Lee J.I. 한국진공학회 2006 Applied Science and Convergence Technology Vol.15 No.2

전류 차단층으로서 AlAs 자연산화층 ($AlO_x$) 을 갖는 InGaAs 양자점 (quantum dot) 구조를 분자선 박막 성장법 (molecular-beam epitaxy)과 습식 산화법 (wet oxidation)을 이용하여 제작하였고, 이들 구조의 열처리에 따른 광학적인 특성 변화를 photoluminescence (PL), PL excitation, 그리고 공간 분해능을 갖는 micro-PL을 이용하여 분석하였다. 습식 산화와 열처리 과정을 통해 intermixing된 InGaAs 양자점 영역에서 PL 특성을 조사한 결과, intermixing 되지 않은 영역보다 높은 에너지에서 완만한 PL peak이 추가적으로 관측되었다. 산화되지 않은 (non-oxided) AlAs 아래에 있는 InGaAs 양자점 영역에서는 약 1.1 eV에서 PL emission이 주로 관측되었으나, $AlO_x$와 $SiN_x$에 의해 intermixing 된 InGaAs 양자점 영역에서는 각각 약 1.16 eV와 $1.18{\sim}1.20$ eV 에서의 PL emission도 함께 관측되었다. 실험 결과, $AlO_x$층이 있는 InGaAs 양자점 영역이 산화 되지 않은 AlAs층이 있는 영역에 비해서 intermixing 효과가 크게 작용함을 알 수 있었다. Optical characteristics of InGaAs quantum dot (QD) laser structures with an Al native oxide (AlOx) layer as a current-blocking layer were studied by means of photoluminescence (PL), PL excitation, and spatially-resolved micro-PL techniques. The InGaAs QD samples were first grown by molecular-beam epitaxy (MBE), and then prepared by wet oxidation and thermal annealing techniques. For the InGaAs QD structures treated by the wet oxidation and thermal annealing processes, a broad PL emission due to the intermixing effect of the AlOx layer was observed at PL emission energy higher than that of the non-intermixed region. We observed a dominant InGaAs QD emission at about 1.1 eV in the non-oxide AlAs region, while InGaAs QD-related emissions at about 1.16 eV and $1.18{\sim}1.20eV$ were observed for the AlOx and the SiNx regions, respectively. We conclude that the intermixing effect of the InGaAs QD region under an AlOx layer is stronger than that of the InGaAs QD region under a non-oxided AlAs layer.

이온빔 보조에 의한 Al 표면의 에칭 및 산화막 형성

김종민,권봉준,이주선,김명원,김무근,오성근 한국진공학회 2000 한국진공학회 학술발표회초록집 Vol.- No.-

Activated Reactive Evaporation에 의한 알루미늄 산화막 형성

김종민,권봉준,박은희,이주선,이혜영,김명원 한국진공학회 2000 한국진공학회 학술발표회초록집 Vol.- No.-

Ion Plating에 의한 알루미늄 산화막 형성

김종민,권봉준,황도진,김명원 한국진공학회 1999 한국진공학회 학술발표회초록집 Vol.- No.-

Carrier dynamics in ZnO/ZnMgO multiple quantum well structures with different well widths grown on ZnO substrates

이송매,권봉준,곽호상,김려화,조용훈,박영신,한명수,박영식 한국진공학회 2009 한국진공학회 학술발표회초록집 Vol.37 No.-

RF 전력제한기용 실리콘 PIN 다이오드 패키지의 열적 거동 분석

백문철,김예빛,권봉준,조성배,정인용,하재권 한국물리학회 2023 새물리 Vol.73 No.6

In this study, we characterized the thermal behavior of a silicon PIN diode package used for a radio-frequency (RF) power limiter. The PIN diode was fabricated using a silicon process and designed to have a breakdown voltage of 250 V. A sequence of five RF pulses with a frequency of 2.7 GHz and a pulse width of 200 μs entered into the RF power limiter circuit, and the output power was measured. Then, the reflected and absorbed powers were respectively obtained using the scattering parameter (S-parameter) matrix. The absorption power proportion showed a slight decrease from 35% to 21.6% as the input power increased. Heat generation and temperature changes in the PIN diode package were analyzed by setting up a simple model and compared with the values actually measured by an infrared thermometer. The peak temperatures of the PIN diode package due to the heat absorbed by the RF pulses showed an almost linear increase when the RF input power increased from 30 to 59 dBm (1 to 810 W). The values calculated by the model matched well with the actual, measured ones within the error range. The temperature profiles of the package caused by input RF pulses were determined using the thermal time constant of the package material and showed a good match when the thermal time constant value was 3.2 ms.

수열합성법과 고상반응법으로 제조한 SrAl2O4:Eu2+ 형광체의 결정 및 광학적 특성

우현주,박지연,권봉준,장기완,문병기 한국물리학회 2014 새물리 Vol.64 No.7

수열합성법과 고상반응법을 이용하여 SrAl2O4:Eu2+ 형광체를 제조하고, 제조법에 따른 결정성과 광학적 특성에 대하여 연구하였다. 시료에 대한 결정구조 및 모양은 XRD 및 FE-SEM을 이용하여 분석하였고 광학적 특성은 여기 및 발광스펙트럼 등의 측정을 통하여 분석하였다. 수열합성법으로 제조된 시료는 비교적 균일한 얇은 판 형태인 낙엽모양으로, 최소 폭이 약 500 nm, 최대 폭은 약 1 μm 그리고 두께가 수 나노미터 정도의 분말결정이었으며 고상반응법으로 제조된 시료는 직경이 약 5 ~10 μm로서 균일하지 못한 괴상형태를 띄고 있었다. 제조된 시료들에 대한 여기스펙트럼은 429 nm에서 최대 여기 피크를 보이면서 선폭이 300 ~ 450 nm로서 비교적 넓으며, 발광스펙트럼은 선폭이 약 450 ~ 650 nm이며 520 nm에서 가장 강하게 나타났다. 또한 365 nm의 UV 램프로 조사 시에 장잔광 특성을 보였다. Eu2+-doped monoclinic Sr1−xAl2O4 powder samples were prepared by using both the solid-state reaction and the hydrothermal methods, followed by sintering at 1300 C for 4 h in a reducing atmosphere (95% N2 + 5% H2). X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were carried out to reveal the phase purity and the morphology of the synthesized phosphors, respectively. The XRD patterns of the SrAl2O4:Eu2+ phosphors agree well with these for the monoclinic SrAl2O4 structure (JC-PDS No: 34-0739). The FE-SEM image of the SrAl2O4:Eu2+ phosphor synthesized by using a solid-state reaction appears to be irregular in shape and agglomerated with an average crystallite size in the range of 1 - 5 μm. The particle prepared by using the hydrothermal method consists of many of agglomerated feather-shaped structures with lengths of 500 nm and widths of 10 nm. Emission and excitation spectra were measured for the synthesized phosphors by using a RF-5301 shimadzu fluorescence spectrofluorophotometer. The decay dynamics and the afterglow properties of the SrAl2O4:Eu2+ phosphors, in addition to the fluorescent properties were also investigated and are discussed in detail.

레이저 기반 테라헤르츠 시간영역 분광 및 영상 기술

강광용 ( Kwang-yong Kang ),권봉준 ( Bong-joon Kwon ),백문철 ( Mun Cheol Paek ),강경곤 ( Kyeong Kon Kang ),조수영 ( Jangsun Kim ),김장선 ( Suyoung Cho ),이승철 ( Senung-churl Lee ),이대성 ( Dae-sung Lee ) 한국센서학회 2018 센서학회지 Vol.27 No.5

THz 시간 영역 분광학(TDS)은 이제 성숙한 분야가 되었고, 그 기술은 전 세계적으로 수백 개의 연구실에서 사용되고 있지만, THz 시스템의 개선에 대한 여지는 아직 많이 남아있다. 도전과제의 핵심은 모드-잠김 에지 방사(edge emitting) 반도체방출 반도체 레이저와 광전도 반도체 양자 구조의 개선이다. 또한 대량 생산을 위한 기술과 3D 프리팅과 같은 혁신적인 제조 기술도 매우 효과적이다. 최근에 상용제품으로 출시된 OSCAT 시스템과 ASOPS 시스템을 이용하여 분광/영상기법을 반도체 패키지 칩에 적용하기도 하였다. 한편, THz 분광법이 정적(static)이거나 또한 시간-분해적이든 간에 모두 반도체 소재 및 반도체 나노 구조의 특성을 평가하는 데 있어서 선도적인 기법이 될 것이다. 향후에는 점점 더 좁은 영역을 탐구하는 방법이나 THz 응용 시스템을 평형상태에서 벗어나게 하는 툴(tool)로써 사용될 가능성도 높다. 또한 메타(meta) 물질을 이용하여 THz 시스템에 적용할 경우, 가변 필터와 같은 순시적인 광학 부품이 가능하므로 광여기(photoexcited) 반도체 소자(신호원)으로 이용하는 구상/디자인도 할 수 있다. Terahertz (THz) time-domain spectroscopy(TDS), imaging techniques, and related systems have become mature technologies, widely used in many universities and research laboratories. However, the development of creative technologies still requires improved THz application systems. A few key points are discussed, including the innovative advances of mode-locking energy-emitting semiconductor lasers and better photoconductive semiconductor quantum structures. To realize a compact, low cost, and high performance THz system, it is essential that THz spectroscopy and imaging technologies are better characterized by semiconductor and nano-devices, both static and time-resolved. We introduce the THz spectroscopy and imaging systems, the OSCAT(Optical Sampling by laser CAvity Tuning) system and the ASOPS(ASynchronous Optical Sampling) system, are constructed by our research team. We report on the THz images obtained from their use.