• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.17-22
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• 1999

Since the use of porous silicon for microsensors and microactuators is in the euly stage of study, only several application devices, such as light-emitting diodes and chemical sensors have so far been demonstrated. In this paper we present an overview of the present status of porous silicon sensors and actuators research with special emphasis on the applications of chemical sensors and optical devices. The capacitive type porous silicon humidity sensors had a nonlinear capacitance-humidity characteristic and a good sensitivity at higher humidity above $40\%RH$. The porous silicon $n^+-p-n^+$ device showed a sharp increase in current when exposed to an ethanol vapor. The $p^+-PSi-n^+$ diode fabricated on porous silicon diaphragm exhibited an optical switching characteristic, opening up its utility as an optical sensor or switch. The photoluminescence (PL) spectrum, taken from porous silicon under 365 nm excitation, had a broad emission, peaked at -610 nm. The electroluminescence(EL) from ITO/PSi/In LED had a broader spectrum with a blue shifted peak at around 535nm than that of the PL.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.553-557
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• 1999

In order to investigate the optical properties of the $Al_XGa_{1-X}N/GaN$ thin film grown by metalorganic chemical vapor deposition (MOCVD) method, the photoluminescene (PL), photocurrent (PC) and persistent photoconductivity (PPC) measurements were carried out at room temperature. The band gap of the $A1_x$$Ga_{1-x}$N/GaN was determined to 3.70 eV by the PL and PC measurements. The PC measurement on the light illumination from the top of the $A1_x$$Ga_{1-x}$N/GaN thin film provides peaks at 3.70, 3.43, and around 2.2 eV. The PC spectrum by the illumination passing through from the substrate of the sample can be shown at 3.43 eV together with a broad tail band from the GaN band edge to around 2.23 eV. The photocurrent quenching and anomalous PPC decay observed in PPC measurements indicate that metastable electron states are fomed in the band gap of GaN layer to trap electrons which can be tunneled the potential barrier for long recovery time.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.209-215
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• 2006

We investigated the optical property and the electronic subband structure of InAs quantum dots in an InAsGa/GaAs well structure utilizing photoluminescence (PL), PL excitation (PLE) and near infrared transmission spectroscopy. From transmission and PLE spectra, we found three bound states in the InAs quantum dot and two bound states in InGaAs/GaAs quantum well, and correlated to the results of intersubband transitions observed in photocurrent spectrum.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.541-546
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• 2006

In this study we have investigated cathodoluminescence (CL) and structural properties of thin film $ZnGa_2O_4:Mn$ oxide phosphor by using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), photoluminescence (PL), and cathodoluminescence. PL emission peaked at 506 nm was observed from the $ZnGa_2O_4:Mn$ phosphor target and it was attributed to the $^4T_1-^6A_1$ transition in $Mn^{2+}$ ion. The color coordinates of the emission were x = 0.09 and y = 0.67. The $ZnGa_2O_4:Mn$ films showed the excitation spectrum peaked at 294 nm by $Mn^{2+}$ ion absorption. It was found that the higher intensity of CL emission at 505 nm appears to result from the denser and closely-packed structure in $ZnGa_2O_4:Mn$ phosphor films deposited at lower pressures. The CL intensity did not show any systematic dependence on film surface roughness.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.31-34
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• 2002

HgTe quantum dots were synthesized in aqueous solution at room temperature by colloidal method. The synthesized materials were identified to be zincblende cubic structured HgTe quantum dots by X-ray diffraction and transmission electron microscopy image revealed that these quantum dots are agglomerate of a individual particle. The colloidally prepared HgTe quantum dots have the sphere-like shape with a diameter of approximately 4 nm. The optical properties of the HgTe quantum dots were investigated with photoluminescence(PL). The PL appears in the near-infrared region, which represent a dramatic shift from bulk HgTe behavior. The analytic results revealed that HgTe quantum dots have the broad size distribution, as PL emission spectrum covers the spectral region from 900 to 1400 nm. In this study, the factors affecting PL of HgTe quantum dots and particle size distributiont are described.會Ā᐀䁇?⨀젲岒Ā㰀會Ā㰀顇?⨀끩Ā㈀會Ā㈀?⨀䡪ఀĀ᐀會Ā᐀䡈?⨀Ā᐀會Ā᐀ꁈ?⨀硫ᜀĀ저會Ā저?⨀샟ගऀĀ저會Ā저偉?⨀栰岒ఀĀ저會Ā저ꡉ?⨀1岒Ā저會Ā저J?⨀惝ග؀Ā؀會Ā؀塊?⨀ග嘀Ā切會Ā切끊?⨀⣟ගĀ搀會Ā搀ࡋ?⨀큭킢Ā저會Ā저恋?⨀桮킢Ā저會Ā저롋?⨀⣅沥ࠀĀࠀ會Āࠀ၌?⨀샅沥Ā저會Ā저桌?⨀壆沥ሀĀ저會Ā저쁌?⨀o킢瀀ꀏ會Āᡍ?⨀棤좗ĀĀĀ會ĀĀ灍?⨀å좗ĀĀĀ會ĀĀ졍?⨀飥좗ĀĀĀ會ĀĀ⁎?⨀?ꆟᤀ

• Journal of Life Science
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• v.25 no.1
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• pp.53-61
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• 2015

In this study, we tried to separate the photosensitizer that induces apoptosis of leukemia cells (U937) from perilla leaves. Perilla leaves (Perilla frutescens Britt var. japonica Hara) are a popular vegetable in Korea, being rich in vitamins (A and E), GABA, and minerals. Dried perilla leaves were extracted with methanol to separate the photosensitizer by various chromatographic techniques. The structure of the isolated compound (PL9443) was identified by 1D-NMR, 2D-NMR, and FAB-mass spectroscopy. Absorbance of the UV-Vis spectrum was highest at 410 nm and was confirmed by the 330, 410, and 668 nm. PL9443 compound was determined to be pheophorbide, an ethyl ester having a molecular weight of 620. It was identified as a derivative compound of pheophorbide structure when magnesium comes away from a porphyrin ring. Observation of morphological changes in U937 cells following cell death induced by treated PL9443 compound revealed representative phenomena of apoptosis only in light irradiation conditions (apoptotic body, vesicle formation). Results from examining the cytotoxicity of PL9443 substance against U937 cells showed that inhibition rates of the cell growth were 99.9% with the concentration of 0.32 nM PL9443. Also, the caspase-3/7 activity was 99% against U937 cells with the concentration of 0.08 nM of PL9443 substance. The result of the electrophoresis was that a DNA ladder was formed by the PL9443. The PL9443 compound is a promising lead compound as a photosensitizer for photodynamic therapy of cancer.

• Journal of the Korean Applied Science and Technology
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• v.15 no.3
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• pp.85-90
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• 1998

In this study, organic electroluminescent devices(OELD) with a structure of a glass $substrate/ITO/TPD/Tb(ACAC)_3(Phen-Cl)/Alq_3/Al$ was fabricated by vacuum evaporation method, where Tb complex was known to have green light emitting property. Electroluminescent(EL) and I-V characteristics of this structure were investigated. This triple-layer structure shows the green EL spectrum at the wavelwngth of 546nm, which is almost the same as the PL spectrum of $Pb(ACAC)_3(Phen_Cl)$. It was found in current-voltage(I-V) characteristics of the devices that the operating voltage was about 12V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.848-850
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• 2001

In this work, we investigated on the white-colored ribbon fiber synthesized from GaN powder. We convinced the formation of monoclinic phase $\beta$-Ga$_2$O$_3$from the X-ray diffraction pattern on ribbon fiber. The 10 K PL spectrum consisted with the strong emission band caused by self-activated optical center at 3.464 eV with the full-width at half maximum of 48 meV and the impurity related emission bands. Through this work, the optical properties and the electrical conductivity of $\beta$-Ga$_2$O$_3$, it will be useful for the fabrication of optoelctronic devices operating in visible spectrum region.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.955-958
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• 2003

We report the photo-(PL) and electroluminescence (EL) properties of new conjugated compounds based on diphenyl benzeneamine moiety, 4,4'-(1,4-phenylenedi-(1E)-2,1-ethenediyl]bis(N,N-diphenyl-benzenamine](PEDB) and 4,4'-([1,1 -biphenyl]-4,4'-diyldi-2,1-ethenediyl)bis[N,N-diphenyl-benzenamine)(BPEDB), as emitting materials and dopant materials. The ITO/m-MTDATA/NPB/DPVBi + BPEDB(1%) /Alq3/LiF/Al device shows blue EL spectrum at 458nm and high efficiency(5.3 cd/A). PEDB as dopant shows also blue EL spectrum around ${\lambda}$ max=463nm and 4.1 cd/A high efficiency in ITO/m-MTDATA/NPB/DPVBi + PEDB(1%)/Alq3/LiF/Al device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.2
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• pp.133-138
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• 2001

We studied the optical properties of poly(3-hexylthiophene) for applying to the emitting material of organic electro luminescent device. The infrared spectrum and NMR of synthesized polymer gave good evidence for the conjugation of 3-hexylthiophene monomer unit. We confirmed that poly(3-hexylthiophene) contains the HT(head-to-tail)-HT(head-to-Tail) linkage larger than 65% based on NMR analysis. FTIR and raman spectroscopy show that poly(3-hexylthiophene) has two main vibration levels which have an energy about 0.18eV and 0.36eV. Electronic absorption spectra shifted to the shorter wavelength with increasing temperature, which is related to a conformational transition of the polymer. Photoluminescence spectrum generated at low temperature(10K) is separated at 669nm, 733nm and 812nm that it's because of phonon energy generated from the lattice vibration.