• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.332-332
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• 2012

분자선 에피탁시(molecular beam epitaxy)를 이용하여 GaAs 기판에 성장한 InAs 양자점(QDs: quantum dots)은 성장 온도, 압력, As/In의 공급비 등의 성장 조건에 따라 다른 변수(parameter)를 갖는다. 따라서 성장변수에 따라 양자점의 모양과 크기, 밀도가 달라져 균일한 양자점 형성에 어려움이 있어 많은 연구가 진행되고 있다. 예를 들면 In-interruption 법으로 성장한 양자점의 특성이 S-K mode (Stranski-Krastanov mode)로 성장한 양자점에 비해 광학적 특성이 향상되었다. 본 연구에서는 In pre-deposition (IPD) 법으로 성장한 InAs/GaAs 양자점의 광학적 특성을 PL(photoluminescence)와 TRPL (time-resolved PL)을 이용하여 분석하였다. InAs QDs 시료들은 In과 As 공급시간을 각각 1초와 19초 (QD1), 2초와 18초 (QD2), 3초와 17초 (QD3)로 조절하여 성장하였으며, In이 공급되는 시간 동안 As shutter를 차단하여 As 공급을 중단하였다. In과 As의 차단 없이 S-K mode로 성장한 시료를 기준시료로 사용하였다 (QD0). AFM (atomic force microscope) 측정결과, In 공급시간이 1초에서 2초로 증가할 때, 양자점의 밀도와 종횡비(aspect ratio)가 증가하였고, 양자점의 균일도가 증가하였다. 그러나 QD3 시료는 QD1 시료에 비해 밀도와 종횡비, 균일도가 감소하였다. 10 K에서 PL 피크는 In 공급 시간이 증가할 때, 970 nm에서 1020 nm로 적색편이 하였고 반치폭 (FWHM: full width at half maximum)은 75 meV에서 85 meV로 증가하였다. QD2 시료의 PL 피크 에너지가 가장 낮았고, 가장 강한 PL 세기를 보였다. IPD 시간이 증가함에 따라 PL 피크에서 측정한 PL 소멸은 점차 빨라졌다. IPD 기법으로 성장한 양자점의 빠른 PL 소멸은 양자점 밀도와 종횡비 향상에 의한 파동함수 중첩의 증가와 구속 에너지 증가에 의한 것으로 설명된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.620-620
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• 2013

When $MoS_2$ is thinned to single layer (1L), photoluminescence (PL) quantum yield drastically increases due to emergence of direct band gap. A recent theory predicts that the electronic structure of 1L $MoS_2$ is very sensitive to its lattice constants. We investigated the response of 1L $MoS_2$ to biaxial tensile strain using spatially resolved PL and Raman spectroscopy. Changes in the lattice constants were monitored by the Raman frequency of the in-plane ($E^1{_2g}$) mode. Systematic correlations between PL and Ramanspectral features, revealed in the preliminary results, will be further tested with samples on other substrates and against thermal stress. The results will also be discussed in regard to the theory which predicts that 1L $MoS_2$ becomes an indirect semiconductor at small tensile strain and turns metallic when further extended.

• Journal of the Korean Ceramic Society
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• v.45 no.2
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• pp.126-131
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• 2008

In this study, we prepared zirconia gel by the sol-gel method and investigated its photoluminescence properties by varying pyrolysis temperature. The addition of acetic acid into a Zr-alkoxide solution resulted in forming the bidentate ligands with Zr ions and producing a stable gel. At the pyrolysis temperature of $350^{\circ}C$, the zirconia nanocrystals with tetragonal structure gradually appeared in the gel. The PL intensity of the zirconia gel increased with increasing the pyrolysis temperature up to $350^{\circ}C$, but decreased above the temperature. Concurrently, its PL peak wavelength continuously shifted from ${\sim}440\;nm$ to ${\sim}550\;nm$ with the temperature. The PL characteristics of the zirconia gels were closely associated with decomposition of residual organic groups, the formation of the zirconia nanocrystals, and the tetragonal to monoclinic phase transformation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.38-41
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• 2002

The variation of photoluminescence(PL) properties of Si thin films was investigated by changing deposition temperatures, Si-rich silicon oxide films on p-type (100) Si substrate have been fabricated by pulsed laser deposition(PLD) technique using a Nd:YAG laser. During deposition, the substrates were kept at the temperature range of room temperature(RT) to $400^{\circ}C$. After deposition, samples were annealed at $800^{\circ}C$ in nitrogen ambient, Strong Blue PL has been observed on RT-deposited Si nanocrystallites. When the deposition temperature was increased over $100^{\circ}C$, PL intensities abruptly decreased. The experimental results show the growing mechanism of Si nanocrystallites by PLD.

• Journal of the Microelectronics and Packaging Society
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• v.4 no.2
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• pp.71-78
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• 1997

본 논문에서는 InGaAsP 에피막에서 도핑 농도와 에피막의 미세조직구조가 photoluminescence (PL) 스펙트럼의 위치 및 형상에 어떤 영향을 미치는가를 연구하였고, 그 결과를 설명하기 위해 가능한 모델을 제시하였다. InGaAsP 에피막(발진파장 ~1.3$\mu$m) 을 액상증착법(liquid phase epitaxy, LPE)으로 성장하여 9K에서 PL측정을 했을 때 InGaAsP 활성층 내 Zn 억셉터의 유무에 따라 PL 피크의 위치가 최대 30nm (24meV)까지 shift하고 피크의 선폭도 넓어지는 현사을 발견하였다. 이와같은 피크 분산현상은 inGaAsP 에피막이 유기금속 기상증착법으로 성장되거나 Zn로 고농도로 도핑되거나 고온에서 어닐링 될 경우 대폭 감소하였다. 이를 설명하기 위해 여러 가지 모델을 설정하여 실험을 하였으며 이 중 InGaAsP 에피막의 미세조직구조 특히 Spinodal 분해에 의한 조성이 모듈레이션과 Zn의 상호작용의 관계가 이 현상을 설명하는 데 가장 적절하다는 것을 밝혔다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.756-759
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• 2009

We described the growth of undoped ZnO thin films and their optical properties changing with a various growth temperature. The undoped ZnO thin films were grown on $c-Al_2O_3$ substrates using pulsed laser deposition (PLD) at room temperature, 200, 400, and $600^{\circ}C$, respectively. Field emission microscopy (FE-SEM) measurements showed that the grain size of undoped ZnO thin films are increasing as a increase of growth temperature. In addition, we were investigated that the structural and optical properties of undoped ZnO thin films by x-ray diffraction (XRD) and photoluminescence (PL) studied. Also, we could confirmed that the exciton luminescence was strongly related to charge trap by grain boundary of the samples using micro-PL measurement.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.387-391
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• 2014

Self-assembled InAlAs/AlGaAs quantum dots (QDs) on GaAs substrates were grown by using modified molecular epitaxy beam in Stranski-Krastanov method. In order to study the structural and optical properties of InAlAs/AlGaAs QDs, atomic force microscopy (AFM) and photoluminescence (PL) measurements are conducted. The size and uniformity of QDs have been observed from the AFM images. The average widths and heights of QDs are increased as the deposition time increases. The PL spectra of QDs are composed of two peaks. The PL spectra of QDs were analyzed by the excitation laser power- and temperature-dependent PL, in which two PL peaks are attributed to two predominant sizes of QDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.663-668
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• 2003

CdTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. The synthesized CdTe QDs were identified to be cubic-structured ones by x-ray diffraction(XRD). The photoluminescence(PL) was performed for CdTe QDs prepared as a function of Te precursor concentration, condensation time and aging time. The PL intensity is strongly dependent on Te precursor concentration, indicating that the ratio of Te to Cd ions affects the particle size and size distribution of the CdTe QDs. Our PL study reveals that the intensity of PL peaks strengthens as the condensation time elongates, implying that annealing by thermal energy transferred during condensation would eliminate defects which act as killing centers in CdTe particles. Our photocurrent study suggests that the CdTe QDs materials are one of the prospective materials for optoelectronics including photodetectors.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.10-13
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• 2001

Effects of an anionic surfactant pentadecafluorooctanoic acid on the photoluminescence of porous silicon was investigated, which was prepared by photoelectrochemical etching at 4V of single crystalline n-type silicon (100) with the specific resistivity of $0.4\~0.8{\Omega}{\cdot}cm$. Photoluminescence shifted to shorter wavelength and its intensity decreased when the concentration of the surfactant increased. FT-IR and contact angle data supported the presence of the surfactant lying on the surface of porous silicon.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.1-5
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• 2007

The 1R(Infra-Red) spectrum and PL(Photoluminescence) of the antiferromagnetic pure $MnF_2$ and the single crystal $MnF_2(1.5%\;EuF_3)$ with the rutile structures were measured. The detailed analysis of the measured PL data showed the differences of the optical property between the single crystal $MnF_2(1.5%\;EuF_3)$ and the pure $MnF_2$. It was found that the additional PL peak by the doping of the $EuF_3$ in $MnF_2$ is originated from the f-d transition of $Eu^{3+}$ from the temperature dependent intensity measurement.