• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.420.2-420.2
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• 2016

Various fields have been paid attention to upconversion nanoparticles (UCNPs) because of its unique optical properties. Moreover, to use the UC luminescent techniques through cell images for identified apoptosis/necrosis of cancer cells have been performed. They have been studied for a versatile biomedical application such as a biosensing tool, or delivery of active forms of medicines inside living cells. UCNPs have distinctive characteristics such as photoluminescence, special emission, low background fluorescence signal and good colloidal stability, which have many advantages compared with the organic dyes and quantum dots. UCNPs have not only a great potential for imaging (UC luminescence) but also therapies (photo-thermal therapy, PTT and photo-dynamic therapy, PDT) in cancer diagnostics. Therefore, we report the enhancement of upconversion red emission in NaYF4:Yb3+,Er3+ nanoparticles, synthesized via solid-state method with the thermal decomposition of trifluoroacetate as precursors and organic solvent at a high boiling point. The UCNPs have an emission in the field of near infrared wavelength, cubic shape and nano-size in length. In this study, we will further investigate it for cancer therapy with NIR optical detection onto the solid substrate.

• 한국결정성장학회지
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• 제17권2호
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• pp.52-56
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• 2007

본 연구에서는 초고진공(UHV, ultra high vacuum) 분자선 에피성장(MBE, molecular beam epitaxy) 시스템을 제작하여, ZnSe/GaAs[001]을 증착하였고, 증착된 박막의 특성을 SEM(scanning electron microscopy), AFM(atomic force microscopy)으로 조사하여, 분자층 단위의 조밀하고 균일한 표면특성을 보이고 있음을 확인할 수 있었다 XRD(x-ray diffractometer)를 이용하여, GaAs[001]기판의 XRD peak 위치와 ZnSe 박막의 XRD peak 위치가 각자 일치함을 확인할 수 있었다. PL(photoluminescence)로는 대략 437nm에서 발광하는 것이 관측되었으며, 2인치 ZnSe 박막의 PL mapping을 측정하였다.

• 한국세라믹학회지
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• 제44권1호
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• pp.32-36
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• 2007

Zinc gallate $(ZnGa_2O_4)$ thin film phosphors have been formed on ITO glass substrates by a sol-gel spinning coating method. For the formation of the film phosphors, the starting materials of zinc acetate dihydrate, gallium nitrate hydrate and 2-methoxyethanol as a solution were used. The thin films deposited were firstly dried at $100^{\circ}C$ and fired at $500^{\circ}C\;or\;600^{\circ}C$ for 30 min and then, annealed $500^{\circ}C\;or\;600^{\circ}C$ at for 30 min under an annealing atmosphere of 3% $H_2/Ar$. The thin films deposited on ITO glass plates showed the (220), (222), (400), (422), (511), and (440) peaks of spinel structure as well as the (311) peak indicating a standard powder diffraction pattern. The surface morphologies of the thin film phosphors were observed with a firing and an annealing condition. The $ZnGa_2O_4$ film phosphors showed the blue emission spectra around 410 nm as well as the emission spectra in the UV region (360-380 nm).

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.245-248
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• 1997

Photoluminescence (PL) and cathodoluminescence (CL) characteristics of Ce-activated $Y_{2-x}Ce_xSiO_5$ have been investigated as functions of Ce concentration and firing condition. According to the X-ray, PL and CL results, $Y_2SiO_5$ is found to have two phases depending on the firing temperature. For the specimen fired above 127$0^{\circ}C$, the emission band peaked at 395nm with a shoulder at 424 nm under ultraviolet (u.v.) and cathode-ray (c.r.) excitation. However, for the specimen fired below 120$0^{\circ}C$ in air the peak was observed at 424 nm and it shifted to longer wavelength with reduction level. The reduced specimen for x=0.02 showed the brightest emission under u.v. excitation whereas under c.r. excitation the brightest emission was observed for the reduced specimen for x=0.06.

• 한국세라믹학회지
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• 제35권7호
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• pp.757-763
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• 1998

The effect of {{{{ {Ga }^{3+ } }} addition on the photoluminescence and cathodoluminescence of {{{{ {SrTiO}_{3 } }}:{{{{ { Pr}^{3+ } }} was stu-died by performing the excitation emission and decay time measurements. Addition of {{{{ {Ga }^{3+ } }} in {{{{ {SrTiO}_{3 } }}:{{{{ { Pr}^{3+ } }} resulted in a considerable enhancement of {{{{ { Pr}^{3+ } }} emission intensity. From the analysis of the experimental results the following mechanism is proposed. Excitation in the {{{{ {SrTiO}_{3 } }} host lattice leads to the formation of electrons in the conduction band and holes in the valence band. The electrons in the conduction band re-combine radiatively with the holes trapped at {{{{ { Ga}^{3+ } }} and the energy is transferred to {{{{ { Pr}^{3+ } }} ion which give its own characteristic red emission.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.39-39
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• 2010

The authors have an extensive study of photoluminescences for Zn-polar and O-polar faces of single-crystalline ZnO bulks. In the photoluminescence (PL) spectra at 10 K, Zn-polar and O-polar faces show a common emission feature: neutral donor-bound excitons and their longitudinal-optical (LO) phonon replicas are strong, and free excitons are very weak. However, in the PL spectra at room temperature (RT), Zn-polar and O-polar faces show extremely different emission characteristics: the emission intensity of Zn-polar face is 30 times larger than that of O-polar face, and the band edge of Zn-polar face is 33 meV red-shifted from that of O-polar face. The temperature dependence of photoluminescence indicates that the PL spectra at RT are closely associated with free excitons and their phonon-assisted annihilation processes. As a result, it is found that the RT PL spectra of Zn-polar face is dominated by the first-order LO phonon replica of A free excitons, while that of O-polar face is determined by A free excitons. This is ascribed that Zn-polar face has larger exciton-phonon coupling strength than O-polar face.

• Current Optics and Photonics
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• 제3권6호
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• pp.516-521
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• 2019

The electrical leakage levels of GaN-based light-emitting diodes (LEDs) containing leakage paths are estimated using photoluminescence (PL) and photovoltaic properties under photoexcitation conditions. The PL intensity and open-circuit voltage (V_OC) decrease because of carrier leakages depending on photoexcitation conditions when compared with reference values for typical LED chips without leakage paths. Changes of photovoltage-photocurrent characteristics and PL intensity due to carrier leakage are employed to assess the leakage current levels of LEDs with leakage paths. The current corresponding to the reduced V_OC of an LED with leakage from the photovoltaic curve of a reference LED without leakage is matched with the leakage current calculated using the PL intensity reduction ratio and short-circuit current of the LED with leakage. The current needed to increase the voltage for an LED with a leakage under photoexcitation from V_OC of the LED up to V_OC of a reference LED without a leakage is identical to the additional current needed for optical turn-on of the LED with a leakage. The leakage current level estimated using the PL and photovoltaic properties under photoexcitation is consistent with the leakage level measured from the voltage-current characteristic obtained under current injection conditions.

• Bulletin of the Korean Chemical Society
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• 제28권8호
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• pp.1280-1284
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• 2007

A series of Ca1-xSrxS:Eu (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) phosphors were synthesized by solid-state reactions. The Ca1-xSrxS:Eu phosphors have a strong absorption at 455 nm, which corresponds to the emission wavelength of a blue LED. The emission peak of Ca1-xSrxS:Eu is blue shifted from 655 to 618 nm with increasing Sr content. The characteristics of Ca1-xSrxS:Eu phosphors make them suitable for use as wavelengthtunable red-emitting phosphors for three-band white LEDs pumped by a blue LED. In support of this, we fabricated a three-band white LED by coating SrGa2S4:Eu and Ca0.6Sr0.4S:Eu phosphors onto a blue LED chip, and characterized its optical properties.

• 한국재료학회지
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• 제15권8호
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• pp.514-517
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• 2005

Effects of nitrogen and oxygen annealing on the carrier concentration, carrier mobility, electrical resistivity and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD). X-ray diffraction (XRD), Scanning electron microscope (SEM), photoluminescence (PL) analyses, and Hall measurement were performed to investigate the crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. According to the XRD analysis results the crystallinity of the ZnO film annealed in an oxygen atmosphere is better than that of the ZnO film annealed in a nitrogen atmosphere. Annealing undoped ZnO films grown by ALD at a high temperature above $600^{\circ}C$ improves the crystallinity and enhances W emission but deteriorates the electrical conductivity of the flms. The resistivity of the ZnO film annealed particularly at $800^[\circ}C$ in a nitrogen atmosphere is much higher than that annealed at the same temperature in an oxygen atmosphere.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.172-172
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• 2008

By thermal evaporation method, well-aligned ZnO nanowires were synthesized on sapphire substrate at $1000^{\circ}C$ with different oxygen flow rate by using pure ZnO powder (99.999 %). The as-synthesized ZnO nanowires were characterized by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The well-aligned nanowires are single crystalline in nature and perpendicularly grown along the c-axis. Also the growth rate of nanowires, such as diameter and length, had a tendency to increase as oxygen flow rate increased. Based on the PL measurement of ZnO nanowires, we found that the near band edge of emission redshifted with the increasing intensity of the defect-related green emission in proportion to the increase of oxygen flow rate. "This research was supported by the Korea Research Foundation Grant funded by the Korean Government(MOEHRD)" (The Regional Research Universities Program/Chungbuk BIT Research-Oriented University Consortium).